Is the Wistar Rat a more Suitable Normotensive Control for SHR to Test Blood Pressure and Cardiac Structure and Function?

Abstract Background: There are divergences in the literature regarding the experimental model (Wistar-WIS or Wistar Kyoto-WKY) to be used as a Spontaneously Hypertensive Rat (SHR) control. The characterization of these models in terms of cardiovascular parameters provides researchers with important tools at the time of selection and application in scientific research. Objective: The aim of this study was to evaluate the use of WIS and WKY as a Spontaneously Hypertensive Rat (SHR) control by assessing the long-term behavior of blood pressure and cardiac structure and function in these strains. Methods: To this end, WIS, WKY, and SHR underwent longitudinal experiments. Blood pressure and body mass were measured every two weeks from the 8th to the 72nd. Echocardiographic analysis was performed in all groups with 16, 48, and 72 weeks of life. After having applied the normality test, the Two-Way ANOVA of repeated measures followed by the Tukey post hoc test was used. A significance level of 5% was established. Results: The WIS group showed higher body mass (p<0.05), while the WKY and SHR presented higher body mass variation over time (p<0.05). SHR exhibited increased values of systolic, diastolic, and mean blood pressure when compared to WKY and WIS, whereas the WKY generally showed higher values than WIS (p<0.05). Regarding the cardiac function, SHR showed reduced values, while the WKY presented an early decrease when compared to WIS with aging (p<0.05). Conclusion: WIS is a more suitable normotensive control for SHR than WKY in experiments to test blood pressure and cardiac structure and function.

Aerobic exercise improves renal fibrosis in spontaneously hypertensive rats / 中国应用生理学杂志

Objective: To study the effects of aerobic exercise training on renal fibrosis in spontaneously hypertensive rats (SHR), and to explore the protective effect of exercise on renal damage in hypertensive rats. Methods: Eight-week-old male SHR and Wistar Kyoto rats of the same age (WKY) were randomly divided into 4 groups (n=6): sedentary WKY control group (WKY-S), sedentary SHR control group (SHR-S), low-intensity exercise group (SHR-L) and medium-intensity exercise group (SHR-M). SHR-L group and SHR-M group were set at a slope of 0° at 14 m/min (35% of the maximum aerobic speed) and 20 m/min (50% of the maximum aerobic speed), running on a sports treadmill for 14 weeks, 5 times a week, and 60 min each time. WKY-S and SHR-S groups were kept quietly. Blood pressure was measured 72 hours after exercise training. And the serum levels of creatinine (Scr) and BUN were detected. The morphology of renal tissue was observed by hematoxylin and eosin (HE) staining. The collagen deposition of renal tissue was observed by Masson staining, and the renal collagen volume fraction (CVF) was calculated. Results: Compared with WKY-S group, blood pressure, serum Scr and BUN, kidney CVF levels and AngⅡ, AT1R, TGF-β, α-SMA, CTGF expressions in SHR-S group were increased significantly (P＜0.05). Compared with SHR-S group, blood pressure, serum Scr and BUN, kidney CVF level and AngⅡ, AT1R, TGF-β, α-SMA, CTGF expressions in SHR-L and SHR-M groups were decreased significantly (P＜0.05) and the decreasing trend was more obvious in SHR-M group (P＜0.05). Conclusion: Aerobic exercise can improve renal fibrosis and renal function in spontaneously hypertensive rats by inhibiting the AngⅡ-AT1R-TGF-β pathway.

Inhibition of the Wnt signaling pathway contributes to the cardiac protection of exercise training in spontaneously hypertensive rats / 生理学报

The objective of this study was to investigate the cardiac protective effect of low-to-moderate intensity exercise training and the role of the Wnt signaling pathway in spontaneously hypertensive rats (SHR). SHR and Wistar-Kyoto (WKY) rats were randomly divided into 5 groups, namely hypertensive control (SHR-S), hypertensive plus exercise training (SHR-E), normal blood pressure control (WKY-S), normal blood pressure plus exercise training (WKY-E) and SHR-E plus Wnt agonist (SHR-E-Wnt). The rats in SHR-E and WKY-E groups underwent low-to-moderate intensity swimming for 16 weeks, and the rats in SHR-E-Wnt group were injected with Wnt agonist 1 through tail vein 4 weeks before the end of swimming. The blood pressure of rats was measured every week. After exercise training, the left ventricular wall thickness and ejection function were measured by ultrasound cardiogram, myocardial structure and collagen fiber changes were observed by HE staining and Masson staining, and the expression levels of β-catenin and Dishevelled-1 (DVL-1) mRNA and protein in left ventricular myocardium were detected by real-time fluorescence quantitative PCR and Western blot, respectively. The results showed that the body weight was decreased (P < 0.05), blood pressure was increased (P < 0.01), heart weight and ventricular wall thickness were increased (P < 0.01), and the left ventricular ejection function was decreased (P < 0.05) in SHR-S group compared with those in WKY-S group. In addition, the heart structure was damaged, collagen fibers were significantly increased, and the mRNA and protein expressions of β-catenin and DVL-1 in the left ventricle were significantly up-regulated in SHR-S group compared with those in WKY-S group (P < 0.01). Compared with those in SHR-S group, the body weight of SHR-E group did not change significantly (P > 0.05), but the blood pressure was decreased (P < 0.01), heart weight and ventricular wall thickness were diminished, ejection function was increased (P < 0.01), myocardial structure injury was significantly improved, collagen fibers were significantly reduced, and mRNA and protein expression levels of β-catenin and DVL-1 in the left ventricle were significantly down-regulated (P < 0.01) in SHR-E group. Importantly, exercise-induced antihypertensive and cardioprotective effects in SHR were blunted by Wnt agonist. These results suggest that low-to-moderate intensity exercise training exerts cardioprotective effects in SHR, possibly through inhibiting the Wnt signaling pathway.

Metabolomic characteristics of spontaneously hypertensive rats under chronic stress and the treatment effect of Danzhi Xiaoyao Powder, a traditional Chinese medicine formula / 中西医结合学报

OBJECTIVE@#Numerous studies have demonstrated the close relationship between chronic stress and blood pressure (BP). Hypertensive subjects exhibit exaggerated reactions to stress, especially higher BP. The mechanisms by which stress affects pre-existing hypertension still need to be explored. Danzhi Xiaoyao Powder (DP), a historical traditional Chinese medicine formula, is a promising treatment for BP control in hypertensive patients under stress. The present study investigated the metabolomic disruption caused by chronic stress and the treatment effect and mechanism of DP.@*METHODS@#Spontaneously hypertensive rats (SHRs) were subjected to chronic restraint stress (CRS) for 4 weeks. BP was measured via the tail-cuff method, and anxiety-like behavior was quantified using the elevated-plus-maze test. Meanwhile, DP was administered intragastrically, and its effects were observed. Global metabolomic analysis was performed using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry, followed by multivariate statistical analysis to detect differential metabolites and pathways.@*RESULTS@#DP alleviated the CRS-induced increase in BP and anxiety-like behavior. Systematic metabolic differences were found among the three study groups. A total of 29 differential plasma metabolites were identified in both positive- and negative-ion modes. These metabolites were involved in triglyceride metabolism, amino acid (phenylalanine, tryptophan, and glycine) metabolism, and steroid hormone pathways.@*CONCLUSION@#These findings expose the metabolomic disturbances induced by chronic stress in SHRs and suggest an innovative treatment for this disorder.

Electroacupuncture Attenuated Phenotype Transformation of Vascular Smooth Muscle Cells via PI3K/Akt and MAPK Signaling Pathways in Spontaneous Hypertensive Rats / 中国结合医学杂志

OBJECTIVE@#To investigate whether the antihypertensive mechanism of electroacupuncture (EA) is associated with attenuating phenotype transformation of vascular smooth muscle cells (VSMCs) via phosphoinositide3-kinase (PI3K)/protein kinase B (Akt) and mitogen-activated protein kinase (MAPK) signaling pathways.@*METHODS@#Eight Wistar-ktoyo (WKY) rats were set as normal blood pressure group (normal group). A total of 32 spontaneous hypertensive rats (SHRs) were randomly divided into 4 groups using random number tables: a model group, an EA group, an EA+PI3K antagonist group (EA+P group), and an EA+p38 MAPK agonist+extracellular signal-regulated kinase (ERK) agonist group (EA+M group) (n=8/group). SHRs in EA group, EA+P group and EA+M group received EA treatment 5 sessions per week for continuous 4 weeks, while rats in the normal and model groups were bundled in same condition. The systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) of each rat was measured at 0 week and the 4th week. After 4-week intervention, thoracic aorta was collected for hematoxylin-eosin (HE) staining, immunohistochemistry [the contractile markers α-smooth muscle actin (α-SMA) and calponin and the synthetic marker osteopontin (OPN)] and Western blot [α-SMA, calponin, OPN, PI3K, phosphorylated-Akt (p-Akt), Akt, p-p42/44 ERK, total p42/44 ERK, p-p38 MAPK and total p38 MAPK].@*RESULTS@#EA significantly reduced SBP, DBP and MAP (P<0.01). HE staining showed that the wall thickness of thoracic aorta in EA group was significantly decreased (P<0.01). From results of immunohistochemistry and Western blot, EA increased the expression of α-SMA and calponin, and decreased the expression of OPN (P<0.01). In addition, the expression of PI3K and p-Akt increased (P<0.01), while the expression of p-p42/44 ERK and p-p38 MAPK decreased in EA group (P<0.01). However, these effects were reversed by PI3K antagonist, p38 MAPK agonist and ERK agonist.@*CONCLUSIONS@#EA was an effective treatment for BP management. The antihypertensive effect of EA may be related with inhibition of phenotypic transformation of VSMCs, in which the activation of PI3K/Akt and the repression of MAPK pathway were involved.

Influence of electroacupuncture on ghrelin and the phosphoinositide 3-kinase/protein kinase B/endothelial nitric oxide synthase signaling pathway in spontaneously hypertensive rats / 中西医结合学报

OBJECTIVE@#To investigate the influence of electroacupuncture (EA) on ghrelin and the phosphoinositide 3-kinase/protein kinase B/endothelial nitric oxide synthase (PI3K/Akt/eNOS) signaling pathway in spontaneously hypertensive rats (SHRs).@*METHODS@#Eight Wistar-Kyoto rats were used as the healthy blood pressure (BP) control (normal group), and 32 SHRs were randomized into model group, EA group, EA plus ghrelin group (EA + G group), and EA plus PF04628935 group (a potent ghrelin receptor blocker; EA + P group) using a random number table. Rats in the normal group and model group did not receive treatment, but were immobilized for 20 min per day, 5 times a week, for 4 continuous weeks. SHRs in the EA group, EA + G group and EA + P group were immobilized and given EA treatment in 20 min sessions, 5 times per week, for 4 weeks. Additionally, 1 h before EA, SHRs in the EA + G group and EA + P group were intraperitoneally injected with ghrelin or PF04628935, respectively, for 4 weeks. The tail-cuff method was used to measure BP. After the 4-week intervention, the rats were sacrificed by cervical dislocation, and pathological morphology of the abdominal aorta was observed using hematoxylin-eosin (HE) staining. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of ghrelin, nitric oxide (NO), endothelin-1 (ET-1) and thromboxane A2 (TXA2) in the serum. Isolated thoracic aortic ring experiment was performed to evaluate vasorelaxation. Western blot was used to measure the expression of PI3K, Akt, phosphorylated Akt (p-Akt) and eNOS proteins in the abdominal aorta. Further, quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to measure the relative levels of mRNA expression for PI3K, Akt and eNOS in the abdominal aorta.@*RESULTS@#EA significantly reduced the systolic BP (SBP) and diastolic BP (DBP) (P < 0.05). HE staining showed that EA improved the morphology of the vascular endothelium to some extent. Results of ELISA indicated that higher concentrations of ghrelin and NO, and lower concentrations of ET-1 and TXA2 were presented in the EA group (P < 0.05). The isolated thoracic aortic ring experiment demonstrated that the vasodilation capacity of the thoracic aorta increased in the EA group. Results of Western blot and qRT-PCR showed that EA increased the abundance of PI3K, p-Akt/Akt and eNOS proteins, as well as expression levels of PI3K, Akt and eNOS mRNAs (P < 0.05). In the EA + G group, SBP and DBP decreased (P < 0.05), ghrelin concentrations increased (P < 0.05), and the concentrations of ET-1 and TXA2 decreased (P < 0.05), relative to the EA group. In addition, the levels of PI3K and eNOS proteins, the p-Akt/Akt ratio, and the expression of PI3K, Akt and eNOS mRNAs increased significantly in the EA + G group (P < 0.05), while PF04628935 reversed these effects.@*CONCLUSION@#EA effectively reduced BP and protected the vascular endothelium, and these effects may be linked to promoting the release of ghrelin and activation of the PI3K/Akt/eNOS signaling pathway.

Involvement of ET-1/eNOS in the ameliorating effect of electroacupuncture on cardiac dysfunction in rats with spontaneously hypertensive / 中国针灸

OBJECTIVE@#To observe the effect of electroacupuncture (EA) at "Neiguan" (PC 6) on cardiac function of ventriculus sinister in rats with spontaneously hypertensive (SHR), and to explore the mediation effect of endothelin-1 (ET-1)/endothelial nitric oxide synthase (eNOS).@*METHODS@#Six 12-week-old male Wistar Kyoto (WKY) rats were taken as the normal group. Eighteen 12-week-old SHR were randomly divided into a model group, an EA group and a sham EA group, 6 rats in each group. The rats in the EA group were treated with EA (disperse-dense wave, 2 Hz/15 Hz in frequency, 1 mA in current intensity) at "Neiguan" (PC 6), 30 min each time, once a day for 8 weeks. The rats in the sham EA group were treated with superficial needling at "Neiguan" (PC 6) with no electrical stimulation applied. After treatment, the left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) were tested by echocardiographic analysis. The left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), heart rate (HR), the maximum rate of increase/decrease of left ventricular pressure (±dp/dtmax) were detected. The serum content of ET-1 was detected by ELISA. Western blot was used to evaluate the expression of ETAR, eNOS in myocardial tissue of left ventricular.@*RESULTS@#Compared with the normal group, LVEF, LVFS, +dp/dtmax/LVSP and -dp/dtmax/LVSP were decreased (P<0.01, P<0.05), while LVSP, LVEDP, +dp/dtmax and -dp/dtmax were increased (P<0.01) in the model group. Compared with the model group, LVEF, LVFS, +dp/dtmax/LVSP and -dp/dtmax/LVSP were increased (P<0.01, P<0.05), and LVSP and LVEDP were decreased (P<0.01) in the EA group. Compared with the normal group, the serum content of ET-1 and the expression of ETAR in myocardial tissue were increased (P<0.01), whereas expression of eNOS was decreased (P<0.01) in the model group. Compared with the model group, the serum content of ET-1 and the expression of ETAR in myocardial tissue were decreased (P<0.05), whereas expression of eNOS was increased (P<0.05) in the EA group.@*CONCLUSION@#EA intervention may alleviate hypertensive cardiac function damage by up-regulating the expression of eNOS protein in myocardial tissue, down-regulating the serum content of ET-1 and the expression of ETAR protein in myocardial tissue.

Interleukin-17A is closely correlated with the progression of renal epithelial-mesenchymal transition in spontaneously hypertensive rats / 南方医科大学学报

OBJECTIVE@#To explore the role of interleukin-17A (IL-17A) in renal epithelial- mesenchymal transition (EMT) in essential hypertensive nephropathy.@*METHODS@#Four-week-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats (control group) were both randomized into 4 groups (n=5) for observation at 4, 6, 10 and 30 weeks of age. Blood pressure of the rats was monitored using a noninvasive tail artery blood pressure measurement instrument. The percentage of Th17 cells in the splenocytes was analyzed using flow cytometry. The mRNA and protein expression levels of IL-17A, iNOS, Arg-1, E-cadherin, and α-SMA in the kidneys of the rats were detected using RT-PCR and immunohistochemical staining, respectively, and plasma levels of IL-17A were regularly detected using ELISA.@*RESULTS@#At the age of 6 weeks, the SHRs began to show significantly higher blood pressure with greater Th17 cell percentage in the splenocytes and high renal expression and plasma level of IL-17A than WKY rats (P < 0.05 or P < 0.01). At 30 weeks, renal expression of E-cadherin mRNA and protein was significantly lower and the expression of Arg-1 mRNA and protein was significantly higher in SHR than in WKY rats (P < 0.01). Compared with the WKY rats, the SHRs showed significantly higher mRNA and protein expressions of iNOS at 6 and 10 weeks (P < 0.05 or 0.01) and higher α-SMA mRNA and protein expressions since 10 weeks of age (P < 0.05 or 0.01). In SHRs older than 10 weeks, renal IL-17A mRNA and protein expression levels were negatively correlated with those of E-cadherin (r=-0.731, P < 0.05; r=-0.827, P < 0.01) and positively correlated with those of α-SMA (r=0.658, P < 0.05; r=0.968, P < 0.01).@*CONCLUSION@#IL-17A is closely correlated with the progression of renal EMT in SHR and plays its role possibly by mediating M1/M2 polarization of renal infiltrating macrophages.

The effects of methanol extract of Galium verum L on cardiac redox state in hypertensive rats

Abstract The aim of this study was to assess the effects of methanol extract of G. verum on redox status of isolated heart of spontaneously hypertensive rats after ischemia. Twenty-four Wistar albino rats were divided into three groups: untreated control rats and rats that received 125 and 250 mg/kg G. verum extract for 4 weeks per os. Index of lipid peroxidation (measured as TBARS) and parameters of antioxidative defence system such as level of reduced glutathione (GSH) and activities of catalase (CAT) and superoxide dismutase (SOD) were spectrophotometrically determined in heart homogenate. The index of lipid peroxidation in heart tissue was lower in both treated groups compared to the control group. On the other hand, the activity of SOD was significantly higher after consumption of both doses, while the activity of CAT was significantly higher only after treatment with a higher dose of extract. Based on our results we might conclude that 4-week treatment with methanol extracts of G. verum has the potential to modulate myocardial redox signaling after ischemia, thus significantly alleviating cardiac oxidative stress and exerting dose-dependent antioxidant properties. Future studies are certainly necessary to fully clarify the role of this plant species in myocardial I-R injury.

A method to assess heart rate variability in neonate rats: validation in normotensive and hypertensive animals

Several studies have focused on the heart rate variability (HRV) of murine species, while studies discussing HRV in murine neonates and infants remain scarce, since recording hemodynamic signals through invasive methods in small animals has been found to be quite challenging. Thus, this study aimed at describing and validating a novel method to assess HRV in newborn rats. An electrocardiogram (ECG) system was used to determine RR intervals in awake newborns and evaluate HRV in normotensive (Wistar) and hypertensive (SHR) neonate rats. After birth, ECG was recorded in the awake newborns, and they were allowed to rest on a heated surface, restricted only by the weight of the adhesive ECG electrodes. The electrodes were cut and adapted to provide more comfort to the animal, and gently placed on the newborn's skin. RR intervals were recorded over a 30-min period using an ECG system together with LabChart software (4 KHz). Three sequences of 5 min each from the ECG recording period were analyzed in time and frequency domains, using CardioSeries software. ECG data resulted in a clearly interpretable signal that was used to generate an RR interval sequence through time for the analysis of HRV. SHR neonates presented increased cardiac sympathovagal balance compared to Wistar neonates (low frequency/high frequency: 3.85±0.71 vs 0.90±0.09). In conclusion, the ECG setup here described may be used to record RR intervals to assess HRV in neonate rats, thus detecting early impairment of HRV in hypertensive newborns.

Tyrosine hydroxylase and ß2-adrenergic receptor expression in leukocytes of spontaneously hypertensive rats: putative peripheral markers of central sympathetic activity

The sympathetic nervous system (SNS) plays a fundamental role in the pathophysiology of cardiovascular diseases, including primary arterial hypertension. In this study, we aimed to investigate whether the expression of the rate-limiting enzyme in catecholamine synthesis, tyrosine hydroxylase (TH), and the β2-adrenergic receptor (β2-AR) in immune cells from peripheral blood, reflect central SNS activity in spontaneously hypertensive rats (SHR). TH expression in the lower brainstem and adrenal glands and β2-AR expression in the lower brainstem were analyzed by western blot analyses. In the leukocytes, TH and β2-AR expression was evaluated by flow cytometry before and after chronic treatment with the centrally-acting sympathoinhibitory drug clonidine. Western blot analyses showed increased TH and β2-AR expression in the lower brainstem and increased TH in adrenal glands from SHR compared to normotensive Wistar Kyoto rats (WKY). Lower brainstem from SHR treated with clonidine presented reduced TH and β2-AR levels, and adrenal glands had decreased TH expression compared to SHR treated with vehicle. Flow cytometry showed that the percentage of leukocytes that express β2-AR is higher in SHR than in WKY. However, the percentage of leukocytes that expressed TH was higher in WKY than in SHR. Moreover, chronic treatment with clonidine normalized the levels of TH and β2-AR in leukocytes from SHR to similar levels of those of WKY. Our study demonstrated that the percentage of leukocytes expressing TH and β2-AR was altered in arterial hypertension and can be modulated by central sympathetic inhibition with clonidine treatment.

Thermoregulation in Hypertensive Rats during Exercise: Effects of Physical Training / Termorregulação durante o Exercício em Ratos Hipertensos: Efeitos do Treinamento Físico

Abstract Background: Spontaneously hypertensive rats (SHR) show deficit in thermal balance during physical exercise. Objective: To assess the effects of low-intensity physical exercise training on thermal balance of hypertensive rats undergoing an acute exercise protocol. Methods: Sixteen-week-old male Wistar rats and SHR were allocated into four groups: control Wistar rats (C-WIS), trained Wistar (T-WIS), control SHR (C-SHR) and trained SHR (T-SHR). Treadmill exercise training was performed for 12 weeks. Blood pressure, resting heart rate and total exercise time was measured before and after the physical exercise program. After the exercise program, a temperature sensor was implanted in the abdominal cavity, and the animals subjected to an acute exercise protocol, during which internal body temperature, tail skin temperature and oxygen consumption until fatigue were continuously recorded. Mechanical efficiency (ME), work, heat dissipation threshold and sensitivity were calculated. Statistical significance was set at 5%. Results: Physical training and hypertension had no effect on thermal balance during physical exercise. Compared with C-WIS, the T-WIS group showed higher heat production, which was counterbalanced by higher heat dissipation. Hypertensive rats showed lower ME than normotensive rats, which was not reversed by the physical training. Conclusion: Low-intensity physical training did not affect thermal balance in SHR subjected to acute exercise.

Resumo Fundamento: Ratos espontaneamente hipertensos (SHR) apresentam déficits no balanço térmico durante o exercício físico. Objetivo: Avaliar os efeitos do treinamento físico de baixa intensidade sobre o balanço térmico de ratos hipertensos submetidos a um protocolo de exercício físico agudo. Métodos: Ratos machos Wistar e SHR, com 16 semanas de idade, foram divididos em quatro grupos experimentais: Wistar controle (WIS-C), Wistar treinado (WIS-T), SHR controle (SHR-C) e SHR treinado (SHR-T). O treinamento físico em esteira rolante foi realizado durante 12 semanas. A pressão arterial, a frequência cardíaca de repouso e o tempo de exercício foram medidos previamente e após o programa de treinamento físico. Após o programa de treinamento físico, um sensor de temperatura foi implantado na região intraperitoneal e os ratos foram submetidos a um protocolo de exercício físico agudo com registros contínuos da temperatura corporal interna, temperatura da pele da cauda e do consumo de oxigênio até a fadiga. A eficiência mecânica (EM), o trabalho, o limiar e a sensibilidade para dissipação de calor foram calculados. Para as análises estatísticas o nível de significância adotado foi de 5%. Resultados: O treinamento físico e a hipertensão arterial não alteraram o balanço térmico durante o exercício físico. O grupo WIS-T quando comparado ao WIS-C, apresentou maior produção de calor, que foi contrabalanceado por uma maior dissipação de calor. Os animais hipertensos apresentaram menor EM em comparação aos animais normotensos, e o treinamento físico não foi capaz de reverter esta alteração. Conclusão: O treinamento físico de baixa intensidade não provocou alterações no balanço térmico de ratos hipertensos submetidos a um protocolo de exercício físico agudo.

Effects of Chronic Exposure to Mercury on Angiotensin-Converting Enzyme Activity and Oxidative Stress in Normotensive and Hypertensive Rats / Efeitos da Exposição Crônica ao Mercúrio sobre a Atividade da Enzima Conversora de Angiotensina e Estresse Oxidativo em Ratos Normotensos e Hipertensos

Abstract Background: Mercury's deleterious effects are associated with increased cardiovascular risk. Objective: To determine whether chronic exposure to inorganic mercury increases the activity of angiotensin-converting enzyme and its relationship with oxidative stress in several organs and tissues. Methods: We studied male Wistar and spontaneously hypertensive rats (SHR) (3-month-old) exposed or not to HgCl2 for 30 days. At the end of treatment, we investigated the following: changes in body weight, hemodynamic parameters, angiotensin-converting enzyme (ACE) activity and oxidative stress in the heart, aorta, lung, brain and kidney in hypertensive compared to normotensive animals. A value of p < 0.05 was considered significant. Results: Chronic exposure to HgCl2 did not affect weight gain in either group. Systolic blood pressure, measured weekly, did not increase in Wistar rats but showed a small increase in SHR rats. We also observed increases in left ventricular end-diastolic pressure and ACE activity in the plasma and hearts of normotensive rats. In the SHR+Hg group, ACE activity increased in plasma but decreased in kidney, lung, heart, brain and aorta. Oxidative stress was assessed indirectly by malondialdehyde (MDA) production, which increased in Hg-treated rats in both plasma and heart. In the SHR+Hg group, MDA increased in heart and aorta and decreased in lungs and brain. Conclusion: These results suggest that chronic exposure to inorganic mercury aggravates hypertension and produces more expressive changes in ACE activity and oxidative stress in SHRs. Such exposure affects the cardiovascular system, representing a risk factor for the development of cardiovascular disorders in normotensive rats and worsening of pre-existing risks for hypertension.

Resumo Fundamento: Os efeitos deletérios do mercúrio estão associados ao risco cardiovascular aumentado. Objetivo: Determinar se a exposição crônica ao mercúrio inorgânico aumenta a atividade da enzima conversora de angiotensina e sua relação com o estresse oxidativo em vários órgãos e tecidos. Métodos: Estudamos ratos Wistar e ratos espontaneamente hipertensos (SHR) (3 meses de idade) expostos ou não a HgCl2 por 30 dias. Ao final do tratamento, investigamos: alterações de peso, parâmetros hemodinâmicos, atividade da enzima conversora de angiotensina (ECA) e estresse oxidativo no coração, aorta, pulmão, cérebro e rim de animais hipertensos comparados a animais normotensos. Um valor de p < 0,05 foi considerado significativo. Resultados: A exposição crônica ao HgCl2 não afetou o ganho de peso em nenhum dos grupos. A pressão arterial sistólica, medida semanalmente, não aumentou em ratos Wistar, mas mostrou um pequeno aumento nos ratos SHR. Também observamos aumentos na pressão diastólica final do ventrículo esquerdo e na atividade da ECA no plasma e no coração de ratos normotensos. No grupo SHR + Hg, a atividade da ECA aumentou no plasma, mas diminuiu no rim, pulmão, coração, cérebro e aorta. O estresse oxidativo foi avaliado indiretamente pela produção de MDA, que aumentou nos ratos tratados com Hg tanto no plasma quanto no coração. No grupo SHR + Hg, o MDA aumentou no coração e na aorta e diminuiu nos pulmões e no cérebro. Conclusão: Estes resultados sugerem que a exposição crônica ao mercúrio inorgânico agrava a hipertensão e produz mudanças mais expressivas na atividade da ECA e no estresse oxidativo em SHRs. Essa exposição afeta o sistema cardiovascular, representando um fator de risco para o desenvolvimento de distúrbios cardiovasculares em ratos normotensos e para piorar riscos pré-existentes para hipertensão.

Losartan improves alveolar bone dynamics in normotensive rats but not in hypertensive rats

Abstract Hypertension is one of the main causes of premature death in the world; also, it is associated with several bone alterations. Preclinical studies have demonstrated delayed alveolar bone healing in hypertensive rats. However, losartan has been favorable for consolidation of bone grafts and reduction in active periodontitis. Therefore, losartan is suggested to be effective in bone formation stages, as well as in the synthesis of matrix proteins and mineralization. Objectives: To evaluate the alveolar bone dynamics in hypertensive rats treated with losartan by laser confocal microscopy and histological analysis. Methodology: Thirty-two rats, 16 spontaneously hypertensive rats (SHR) and 16 Wistar albinus rats, treated or not with losartan (30 mg/kg/day) were used. Calcein fluorochrome at 21 days and alizarin red fluorochrome at 49 days were injected in rats (both 20 mg/kg). The animals were submitted to euthanasia 67 days after treatment, and then the right maxilla was removed for laser confocal microscopy analysis and the left maxilla for histological analysis. Results: This study showed a greater calcium marking in normotensive animals treated with losartan in relation to the other groups. Laser confocal microscopy parameters showed higher values of bone volume formed, mineralized surface, active surface of mineralization and bone formation rate in normotensive animals treated with losartan. However, a smaller mineralized surface was observed in all hypertensive animals. Conclusion: Losartan can improve bone mineralization parameters under normal physiological conditions, but the same anabolic effect does not occur under hypertension.

Pharmacological modulation of b-adrenoceptors as a new cardioprotective strategy for therapy of myocardial dysfunction induced by ischemia and reperfusion

Abstract Purpose: To evaluate the cardioprotective response of the pharmacological modulation of β-adrenergic receptors (β-AR) in animal model of cardiac ischemia and reperfusion (CIR), in spontaneously hypertensive (SHR) and normotensive (NWR) rats. Methods: CIR was induced by the occlusion of left anterior descendent coronary artery (10 min) and reperfusion (75 min). The SHR was treated with β-AR antagonist atenolol (AT, 10 mg/kg, IV) 5 min before CIR, and NWR were treated with β-AR agonist isoproterenol (ISO, 0.5 mg/kg, IV) 5 min before CIR. Results: The treatment with AT increased the incidence of VA, AVB and LET in SHR, suggesting that spontaneous cardioprotection in hypertensive animals was abolished by blockade of β-AR. In contrast, the treatment with ISO significantly reduced the incidence of ventricular arrhythmia, atrioventricular blockade and lethality in NWR (30%, 20% and 20%, respectively), suggesting that the activation of β-AR stimulate cardioprotection in normotensive animals. Serum CK-MB were higher in SHR/CIR and NWR/CIR compared to respective SHAM group (not altered by treatment with AT or ISO). Conclusion: The pharmacological modulation of β-AR could be a new cardioprotective strategy for the therapy of myocardial dysfunctions induced by CIR related to cardiac surgery and cardiovascular diseases.

Effects of Ramipril on the expression of connexin 43 in cerebral arteries of spontaneously hypertensive rats / 生理学报

The present study was designed to examine whether Ramipril (an inhibitor of angiotensin-converting enzyme) affected spontaneous hypertension-induced injury of cerebral artery by regulating connexin 43 (Cx43) expression. Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) were randomly divided into WKY, WKY + Ramipril, SHR, and SHR + Ramipril groups (n = 8). The arterial pressure was monitored by the tail-cuff method, and vascular function in basilar arteries was examined by pressure myography. Hematoxylin-eosin (HE) staining was used to show vascular remodeling. The expression and distribution of Cx43 was determined by using immunofluorescence and immunohistochemistry analysis. The protein and mRNA levels of Cx43 were examined by Western blot and real-time PCR analysis, respectively. The results showed that chronic Ramipril treatment significantly attenuated blood pressure elevation (P < 0.01, n = 8) and blood vessel wall thickness in SHR (P < 0.01, n = 8). The cerebral artery contraction rate in the SHR group was higher than that in the WKY group (P < 0.05, n = 8). The cerebral artery contraction rate in the SHR + Ramipril group was lower than that in the SHR group (P < 0.05, n = 8). Pretreatment with 2-APB (Cx43 non-specific blocker) or Gap26 (Cx43 specific blocker) significantly decreased the vasoconstriction rate, while pretreatment with AAP10 (Cx43 non-specific agonist) significantly increased the vasoconstriction in the SHR + Ramipril group (P < 0.05, n = 8). In addition, the expression of Cx43 mRNA and protein in cerebral arteries of SHR group was higher than that of WKY group (P < 0.05, n = 8). The mRNA and protein expression of Cx43 in cerebral arteries of SHR + Ramipril group was significantly lower than that of SHR group (P < 0.05, n = 8). These results suggest that Ramipril can down-regulate the expression of Cx43 mRNA and protein in cerebral arterial cells of SHR, lower blood pressure, promote vasodilation, and improve arterial damage and vascular dysfunction caused by hypertension.

Amplified cardiorespiratory activity by hypoxia in conscious spontaneously hypertensive rats / 生理学报

Activation of peripheral respiratory chemoreceptors provokes respiratory and cardiovascular reflexes, providing a novel understanding of pathogenic mechanism of hypertension. Here we hypothesize that activation of peripheral respiratory chemoreceptors by hypoxia causes enhanced cardiorespiratory activity in conscious spontaneously hypertensive rats (SHRs). Using whole body plethysmography in combination with radio telemetry, pulmonary ventilation, arterial blood pressure and heart rate were examined in SHRs and Wistar-Kyoto (WKY) rats. We found that exposure to hypoxia induced greater increases in tidal volume and minute ventilation volume in SHRs compared to WKY rats. In addition, hypoxia caused a robust increase in arterial blood pressure and heart rate in SHRs relative to WKY counterparts. After carotid body denervation, the hypoxic ventilatory response was significantly decreased in both SHRs and WKY rats, but without significant difference between the two strains; moreover, the differences of arterial blood pressure and heart rate changes during hypoxic exposure were statistically insignificant between SHRs and WKY rats. It is concluded that hypoxia remarkably potentiates cardiorespiratory activity in the SHRs, suggesting an enhanced sensitivity of carotid bodies to hypoxia.

Effect of baicalin on growth state of attention deficit hyperactivity disorder animal model and its regulation on Ca MKⅡ and ERK1/2 / 中国中药杂志

The aim of this study was to observe the effect of baicalin on the growth state of attention deficit hyperactivity disorder animal model and its regulation on Ca MKⅡand ERK1/2.In the present study,a total of 40 SHR rats were randomly divided into model group,methylphenidate hydrochloride group,and low,medium,and high dose baicalin groups,with 8 rats in each group.Eight WKYrats were selected as a normal control group.The methylphenidate hydrochloride group(0.07 g·L~(-1))and the low(3.33 g·L~(-1)),medium(6.67 g·L~(-1)),and high dose(10 g·L~(-1))baicalin groups received corresponding drugs by gavage administration according to the body weight(0.015 m L·g~(-1)),while the normal group and the model group received the same volume of normal saline by gavage.Thegavage administration lasted for 4 weeks,twice a day.The body weight of the rats and the amount of remaining feed were weighed daily,and the growth state of the rats was statistically evaluated weekly.Percoll density gradient centrifugation was used to prepare brain synaptosomes and an electron microscope was used to observe their structures.The Ca MKⅡand ERK1/2 protein and mRNA expression levels were detected with Western blot and Real-time PCR methods,respectively.RESULTS: showed that baicalin did not affect the normal eating and weight gain of rats,and the weight gain of rats was even more significant than that in the normal group(P<0.05).In the study of its effects on Ca MKⅡand ERK1/2 protein expression in rat synaptosomes,the expression of both proteins in each drug-administered group was higher than that in the model group(P<0.05);besides,the expression levels of Ca MKⅡand ERK1/2 protein were significantly increased in both baicalin high dose group and the methylphenidate hydrochloride group(P<0.05).The relative expression of Ca MKⅡand ERK1/2 mRNA in synaptosome was detected by PCR.The results showed that medium and high doses of baicalin and methylphenidate hydrochloride significantly increased the relative expression of Ca MKⅡand ERK1/2 mRNA in synaptosomes of SHR rats(P<0.05).In conclusion,baicalin does not affect the normal growth and development of SHR rats,so it is safe for administration.Both baicalin and methylphenidate hydrochloride could up-regulate the relative expression of Ca MKⅡand ERK1/2 in mRNA and protein,and the pharmacodynamic stability of baicalin is in a dose-dependent manner to certain extent.

Study on the Intervention Effects of Pinggan Prescription () on Spontaneously Hypertensive Rats Based on Metabonomic and Pharmacodynamic Methods / 中国结合医学杂志

OBJECTIVE@#To investigate the effects of Pinggan Prescription (, PGP) on hypertension by the associated methods of metabonomic and pharmacodynamic.@*METHODS@#A total of 32 male spontaneously hypertensive rats (SHRs) were randomly divided into two groups by using the random number table method: a treatment group (n=18) and a model group (n=14). The Wistar rats (n=14) were used as the normal group. Different prescription were used to intervene three groups: the treatment group in which PGP extract was administered orally at a dose of 18.336 g/kg (PGP/body weight), and the model group in which physiological saline was administered at the equivalent dose. The same treatment was applied to the normal group as the model group. The blood pressure was measured by tail-cuff method, and pharmacodynamic indexes including cyclic adenosine monophosphate (cAMP) and angiotensin II (Ang II) were tested by enzyme-linked immunosorbent assay. The plasma samples from three groups were detected by gas chromatography-mass spectrometry (GC-MS).@*RESULTS@#Compared with the model group, blood pressure of treatment group was obviously reduced after continuous curing with PGP (P<0.01). The pharmacodynamic results illustrated that the content of Ang II increased with the raised blood pressure and the cAMP expressed the converse trend. After curing with PGP, the content of Ang II decreased, the difference between model group and treatment group was significant (P<0.01), and the cAMP expressed the converse trend. Five potential biomarkers were identified, including arachidonic acid, hexadecanoic acid, elaidic acid, octadecanedioic acid and 9,12-octadecadienoic acid. These metabolites had shown significantly changes as followed: arachidonic acid, hexadecanoic acid and elaidic acid were significantly higher and octadecanedioic acid and 9,12-octadecadienoic acid were lowered in the model group than those in the normal group. After the treatment of PGP, the metabolites had the trends of returning to normal along with the reduced blood pressure.@*CONCLUSIONS@#PGP intervention for hypertension played a major role in the metabolism of arachidonic acid and linoleic acid. Metabonomic with pharmacodynamic methods could be potentially powerful tools to investigate the mechanism of Chinese medicine.