Additional antihypertensive effect of magnesium supplementation with an angiotensin II receptor blocker in hypomagnesemic rats

BACKGROUND/AIMS: Magnesium (Mg) is an essential element for vascular function and blood pressure regulation. Several studies have demonstrated that Mg concentration is inversely associated with blood pressure, and that Mg supplementation attenuates hypertension. The purpose of this study was to evaluate the effect of dietary Mg supplementation on the blood pressure effects of an angiotensin II receptor blocker (ARB) in hypomagnesemic rats. METHODS: Fifty male Sprague-Dawley rats were randomly divided into Mg-deficient (n = 30), normal diet plus Mg (n = 10), and control groups (n = 10). Mg-free, high-Mg, and normal-Mg diets were respectively fed to the rats. After 14 weeks, 10 of the 30 Mg-deficient rats were treated with Mg, 10 Mg-deficient rats received an ARB, and 10 Mg-deficient rats received an ARB plus Mg for 4 weeks. RESULTS: Systolic blood pressure was significantly higher in the Mg-deficient rats than in the control rats at week 14. Hypomagnesemic rats exhibited decreased systolic blood pressure after treatment with Mg, and systolic blood pressure showed a greater decrease after ARB treatment. Treatment with the ARB/Mg combination resulted in the greatest decrease in systolic blood pressure. Mg deficiency did not affect the serum angiotensin II level, but did increase the serum aldosterone concentration. Concomitant Mg/ARB supplementation significantly decreased the elevated serum aldosterone level in hypomagnesemic rats. Kidney tissues of the hypomagnesemic rats revealed mild to moderate inflammatory infiltrates. Mg and/or ARB treatment did not reverse the inflammatory reaction in the kidneys of hypomagnesemic rats. CONCLUSIONS: Concurrent dietary Mg supplementation can enhance ARB-induced blood pressure reduction in rats with hypomagnesemic hypertension.

Renin angiotensin system and cardiac hypertrophy after sinoaortic denervation in rats

OBJECTIVE: The aim of this study was to evaluate the role of angiotensin I, II and 1-7 on left ventricular hypertrophy of Wistar and spontaneously hypertensive rats submitted to sinoaortic denervation. METHODS: Ten weeks after sinoaortic denervation, hemodynamic and morphofunctional parameters were analyzed, and the left ventricle was dissected for biochemical analyses. RESULTS: Hypertensive groups (controls and denervated) showed an increase on mean blood pressure compared with normotensive ones (controls and denervated). Blood pressure variability was higher in denervated groups than in their respective controls. Left ventricular mass and collagen content were increased in the normotensive denervated and in both spontaneously hypertensive groups compared with Wistar controls. Both hypertensive groups presented a higher concentration of angiotensin II than Wistar controls, whereas angiotensin 1-7 concentration was decreased in the hypertensive denervated group in relation to the Wistar groups. There was no difference in angiotensin I concentration among groups. CONCLUSION: Our results suggest that not only blood pressure variability and reduced baroreflex sensitivity but also elevated levels of angiotensin II and a reduced concentration of angiotensin 1-7 may contribute to the development of left ventricular hypertrophy. These data indicate that baroreflex dysfunction associated with changes in the renin angiotensin system may be predictive factors of left ventricular hypertrophy and cardiac failure.

Mayor expresión de la enzima convertidora de angiotensina I homóloga (ECA2) en la pared arterial de ratas con niveles genéticamente elevados de angiotensina II: efectos decandesartán y fasudil / Increased expression of homologous Angiotensin I converting enzyme (ACE2) in the arterial wall of rats with genetically elevated levels of Angiotensin II: effects of candesartan and fasudil

El polimorfismo de la enzima convertidora de angiotensina I (ECA) determina mayor actividad de ECA y niveles de angiotensina (Ang) II en ratas Brown Norway (BN) y menor actividad de ECA y niveles de Ang II en ratas Lewis (L). La relación entre ECA, ECA2, la estimulación del receptor de angiotensina (Ang) II y la vía transduccional Rho A/Rho kinasa no ha sido explorada. Objetivo: Determinar la actividad y expresión de ECA2 y eNOS en la aorta de ratas con niveles genéticamente elevados de ECA y Ang II y los efectos independientes de la inhibición del receptor de Ang II (RAT1) y de Rho kinasa (ROCK). Métodos: Se usaron ratas macho homocigotos de 150 grs BN y L. Para inhibir ROCK, se administró fasudil (100 mg/Kg/día por gavage) y para inhibir el RAT1 se administró candesartán (10 mg/kg/día por gavage) a ratas BN, durante 7 días. Se determinó la presión arterial sistólica (PAS), la actividad circulante de ECA y ECA2 por fluorimetría y la expresión génica de ECA2 y de eNOS por RT-PCR (en unidades de densidad óptica).Resultados como promedio(ES). Conclusión: Los mayores niveles de ECA y AngII están asociados a menor actividad circulante de ECA2 en ratas normotensas. Candesartán y fasudil aumentaron la actividad y expresión génica de ECA2 en la pared arterial de ratas BN, efecto que fue mayor al inhibir ROCK. El aumento de ECA2 se asoció a mayor expresión génica de eNOS independientemente de la vía inhibida. Estos resultados permiten plantear que óxido nítrico y ROCK pudieran ser activadores endógenos de ECA2.

Background: Angiotensin I converting enzyme (ACE) polymorphism is associated with increased ACE activity and angiotensin II (A-II) levels in Brown Norway (BN) rats and decreased ACE and A-II levels in Lewis (L) rats. The relationship of ACE, ACE 2, stimulation of A-II receptor and activity of the Rho A/ Rho kinase transductional pathway is not known. Aim: To determine the activity and expression of ACE 2 and eNOS in the aortic wall of rats with genetically elevated leves of ACE and A-II and the independent effects of A-II receptor (ART2) and Rho kinase (ROCK) inhibition. Methods: Homozygous BN and L male rats wighing 150g were used. Fasudil (100mg/kg/day via gavage) was administer to inhibit ROCK and candesartan (10 mg/Kg/day) was given to inhibit ART1, during 7 days. Systolic blood pressure (SBP, ACE and ACE2 circulating activity was measured by fluorimetry. Genetic expression of ACE2 and eNOS was determined by RT-PCR (optical density units). Results are expressed as mean +/- SEM.

Reduced plasma levels of angiotensin-(1-7) and renin activity in preeclamptic patients are associated with the angiotensin I- converting enzyme deletion/deletion genotype

The relationship between preeclampsia and the renin-angiotensin system (RAS) is poorly understood. Angiotensin I-converting enzyme (ACE) is a key RAS component and plays an important role in blood pressure homeostasis by generating angiotensin II (Ang II) and inactivating the vasodilator angiotensin-(1-7) (Ang-(1-7)). ACE (I/D) polymorphism is characterized by the insertion (I) or deletion (D) of a 287-bp fragment, leading to changes in ACE activity. In the present study, ACE (I/D) polymorphism was correlated with plasma Ang-(1-7) levels and several RAS components in both preeclamptic (N = 20) and normotensive pregnant women (N = 20). The percentage of the ACE DD genotype (60 percent) in the preeclamptic group was higher than that for the control group (35 percent); however, this percentage was not statistically significant (Fisher exact test = 2.86, d.f. = 2, P = 0.260). The highest plasma ACE activity was observed in the ACE DD preeclamptic women (58.1 ± 5.06 vs 27.6 ± 3.25 nmol Hip-His Leu-1 min-1 mL-1 in DD control patients; P = 0.0005). Plasma renin activity was markedly reduced in preeclampsia (0.81 ± 0.2 vs 3.43 ± 0.8 ng Ang I mL plasma-1 h-1 in DD normotensive patients; P = 0.0012). A reduced plasma level of Ang-(1-7) was also observed in preeclamptic women (15.6 ± 1.3 vs 22.7 ± 2.5 pg/mL in the DD control group; P = 0.0146). In contrast, plasma Ang II levels were unchanged in preeclamptic patients. The selective changes in the RAS described in the present study suggest that the ACE DD genotype may be used as a marker for susceptibility to preeclampsia.

Changes in renal angiotensinii level in response to caffeic acid phenethyle ester in diabetic rats and its implications on diabetic nephropathy

Diabetic nephropathy [DN] is a microvascular complication of diabetes that represents a major cause of morbidity and mortality in diabetic subjects and is a leading cause of end-stage renal disease in the western countries. Hyperglycemia and tissue injury increase tissue angiotensin II [Ang II] that stimulates the proliferation of kidney cells and the expression of growth factors or cytokines, which may directly or indirectly contribute to the renal 'changes seen in diabetes. The current study aimed to investigate the effect of caffeic acid phenethyester [CAPE] an active component of bee propolis, on diabetic renal injury via examining its effect on renal and plasma AngH levels, blood glucose and insulin levels, proteinurea, albuminurea, and kidney functions in diabetic rats. This study was performed on 30 male Wister rats [300-325g] in weight. Diabetes was induced in 20 rats using 60mg/kg i.p streptozotocin [STZ] in 20 [microl of 0.05 M sodium citrate, pH 4.5. Ten control healthy rats [Group 1] were injected i.p with - 20 microl of the buffer. Diabetic animals studied in this work were divided into 2 experimental groups [n=10 in each] namely, Group 2 that received no treatment and Group 3 that was injected daily with CAPE 10 microl/kg i.p for 4 weeks. Body weight and blood glucose level were measured at the beginning of the study and then every week for all animals. Blood and 24 hrs urine samples and, kidney tissue were collected at the end of the study for measurement of plasma and kidney tissue Ang II levels, serum insulin, urea and creatinine levels. Proteins, albumin and creatinine levels were also measured in urine. Untreated diabetic rats showed significant increase in blood glucose, and significant decrease in serum insulin levels and they fail to gain weight by the end of the study. In addition they showed significant increase in renal and plasma angiotensin II levels and significant increase in urinary protein and albumin loss with a significant increase in serum urea and creatinine levels in comparison to control rats. CAPE treatment for 4weeks was able to significantly decreased plasma and renal Ang II, and significantly increase serum insulin, and decreased blood glucose levels. In addition both urinary protein and albumin loss decreased significantly in the treated rats. CAPE treatment was able to decrease blood glucose, plasma and renal Ang II levels and to increase serum insulin levels and to ameliorate the manifestations of renal impairment associated with diabetes in rats. This may be through its antioxidant, antiproliferative and anti-inflammatory effects. These findings help us to suggest that supplementation of CAPE as an adjuvant therapy to diabetic persons may be promising in helping a better glycemic control and decreasing the renal complications of this wide spread metabolic disorder

Mayor actividad de NADPH oxidasa vascular en ratas con niveles elevados de enzima convertidora de angiotensina I / Increased activity of vascular NADPH oxidase in rats with elevated levels of angiotensin I converting

Introducción: La actividad de la enzima convertidora de angiotensina I (ECA) está determinada importantemente por un polimorfismo de la misma enzima. Las ratas Brown Norway (BB) tienen mayor actividad de ECA (y niveles de angiotensina II) que ratas Lewis (LL). Debido a que Ang II induce la activación de NADPH oxidasa, se postula que el polimorfismo BB determina mayor actividad de NADPH oxidasa y mayor producción de anión superóxido (O2). Métodos: Se usaron ratas homocigotas BB y LL, que tienen niveles altos y bajos de ECA, respectivamente. La actividad enzimática de ECA plasmática se determinó por fluorimetría. La actividad enzimática de NADPH oxidasa (unidades relativas de luz por segundo, por mg de proteína; URL/seg/mg/ prot) y la producción de O2 (URL) se determinaron por quimioluminiscencia con lucigenina en aorta y miocardio.

effect of growth hormone and insulin-like growth factor-1 on post-ischemic heart failure in rats

Heart failure [HF] is a major complication of virtually all forms of heart diseases. Recently neurohormonal mechanisms have been reported to play the main role in the pathogenesis of heart failure. The present study was designed to assess the possible protective effects of both growth hormone [GH] and insulin-like growth factor-1 [IGF-1] on post ischemia HF in rats. The present study was carried out on 50 male albino rats. Forty rats were subjected to coronary artery ligation and the other ten rats were sham-operated. Eight days after surgical intervention animals that survived were classified into four groups [n=10], first group served as control sham-operated group, the second group consisted of coronary ligated untreated rats, the third and fourth group consisted of coronary ligated rats that received GH and IGF-1 respectively for 6 weeks starting from post-ligation day 8. At the end of the study, each rat was weighed and blood samples were collected from tail vein. Plasma samples were used to determine TNF-alpha, aldosterone, IGF-1 and ANGII concentrations, then rats were sacrificed and the heart was rapidly excised, weighed and heart weight/body weight [HW/BW] ratio was calculated as an index of cardiac hypertrophy. After isolation of the left ventricular papillary muscles for determination of isometric force, left ventricular hydroxyproline [LVHPO] concentration [as a reflection of collagen content], was determined. It was found that non-treated coronary-ligated rats showed a significant increase in HW/BW ratio, plasma TNF alpha, aldosterone, ANGII concentration, and in LVHPO concentration. Also they showed a significant decrease in isometric force of left ventricular papillary muscles and a significant decrease in plasma IGF-1, as compared to sham-operated rats. Treatment of groups III and IV with GH and IGF1 resulted in significant change in HW/BW ratio, plasma aldosterone level and LVHPO concentration, nonsignificant increase in developed tension of isolated left ventricular papillary muscles, significant decrease in plasma TNF-alpha concentration and significant increase in plasma IGF-1 concentration as compared to group II. Also treatment of rats of group III with GH produced in significant change in plasma ANGII level while in group IV, IGF-1 produced a significant decrease in ANGII concentration as compared to group II

Relationship between plasma angiotensin ll, leptin and arterial blood pressure

Obesity and hypertension are 2 closely associated conditions and obesity probably predisposed to hypertension. The mechanism of the association between obesity and hypertension is not clear. The aim of the present study was to clarify the relationship between blood pressure [BP], body mass index [BMI], serum angiotensinII [AGII] and serum leptin levels and to investigate the relation between serum AGII and leptin. This study also aimed to rule out if there is a difference in serum AGII and leptin levels between lean and obese hypertensive females. We measured fasting serum AGII and leptin levels in 16 normotensive lean [LN] females, 25 obese normotensive [ON] females, 12 lean hypertensive [LH] females and 25 obese hypertensive [OH] females. All subjects had no evidence of preexisting cardiovascular disease, were non pregnant, had no previous history of ill health or smoking and were not on antihypertensive therapy. This study was performed in King Abdul-Aziz University Hospital, Jeddah, Kingdom of Saudi Arabia from January 2002 through to January 2003. In lean groups, there were a significant increase in BMI and serum AGII in hypertensive group compared to normotensive group while the serum leptin level was insignificantly higher in hypertensive group than in normotensive group. On the other hand, there was a significant increase in serum AGII, BMI and serum leptin for obese hypertensive compared to obese normotensive group. The mean arterial blood pressure [ABP] was significantly correlated to serum AGII, serum leptin and BMI in all groups. A significant correlation was found between serum AGII and serum leptin if all studied females [LN, LH, ON and OH] or obese females [ON and OH] were analyzed [P=0.000 and 0.04]. However, in lean females [LN and LH] there was no relation between serum AGII and serum leptin. When obesity is present, both serum AGII and serum leptin were strong predictor of BP, which is not the case in lean females in whom only serum AGII is a predictor of BP. Elevation of serum AGII and serum leptin levels when associated with increased BMI may contribute to the pathophysiology of obesity induced hypertension. Further study on leptin resistance in obese persons and its relation to increased ABP has to be carried out

Renin angiotensin aldosterone system and drug allergies complicated with hypotension.

It has been discussed in several studies that non-immunologic factors, such as renin angiotensin aldosterone system (RAAS) may play a role in the pathophysiology of anaphylaxis. This study aimed to determine whether RAAS plays a part in the fall in blood pressure during drug reactions or not. Twenty patients who experienced hypotension during drug reaction and 15 healthy volunteers were enrolled in this study. None of the patients in the study or control groups were under treatment with any drug that was capable of influencing to RAAS. Serum levels of angiotensin-I (A-I), angiotensin-II (A-II), angiotensin converting enzyme (ACE) and aldosterone were measured in both study and control groups. The Mann-Whitney U test was used to compare the results of the groups. There were no statistically significant differences between the groups with respect to A-I, A-II, ACE and aldosterone levels. It was concluded that a fall in blood pressure during drug reaction must be the result of mast cell mediator effects on the vascular wall rather than RAAS impairment.

Correlation between plasma angiotensin II and coronary angiographic findings in patients with essential hypertension

The aim of this work,was to evaluate plasma Ang II level in essential hypertensive patients and to verify its relation to the presence and severity of coronary artery disease. Fifty eight patients with essential hypertension and ischaemic chest pain [group A] together with twelve healthy normotensive volunteers [group B] were included in this study.Thorough clinical examination, resting ECG, plain chest X ray, routine laboratory investigations, angiotensin II [Ang II] serum level and echo-Doppler were done for all individuals. Coronary angiography was done fore the group A patients only. The statistical analysis of the results pointed out, a sign higher level of Ang II in group A [38.3 +/- 2 pmol/L] than in group B [24.9 +/- 9 pmol/L] and that its level in group A patients were positively correlated sign to left ventricular mass index and left ventricular wall motion score index but negatively to E/A ratio. Ang II level was significantly higher in hypertensive patients with coronary artery disease [group AII] [59.1 +/- 2 pmol/L] than those with normal coronaries [groupAI] [31.9 +/- 1 pmol/L]. Group All patients with three vessels disease had a sign higher Ang II level than those with two or one vessel coronary artery disease. Ang II level was sign higher in group All patients with LAD coronary artery lesion than those without. Concluston:Patients with essential hypertension had a significantly higher Ang II level than normotensives. Ang II Level was positively correlated significantly to the presence, number and severity of coronary artery lesion in hypertensive patients. Patients with LAD lesion sign had a higher Ang II level than those without

Radioimmunoassay of angiotensin-II: methodology and standardization.

The study was planned to set up and standardize the radioimmunoassay of Ang-II and to validate the procedure in terms of precision, sensitivity, specificity and recovery. The application of the developed assay was studied in normal healthy volunteers and in patients of renovascular hypertension (RVHT) and renal hypertension (RH). Synthetic human Ang-II was coupled to BSA by carbodimide condensation to get the hapten carrier conjugate which was injected in rabbits to raise the antibodies. The titre of 1:250 showed significant binding (56.79%) and was used for the assay. The sensitivity of the assay was 2 pg/ml and cross-reactivity with analogues of Ang-II was minimum. Mean Ang-II levels in normal subjects was 16 +/- 3.6 pg/ml. In patients of RVHT and RH, the peripheral blood Ang-II levels were found to be 876 +/- 8.6 and 108 +/- 2.3 pg/ml respectively. In patients of unilateral RVHT, renal vein Ang-II levels of the affected side were significantly higher than the unaffected side (P < 0.001). The results indicate that unextracted samples can be successfully utilized to estimate Ang-II levels.

Concentrations of-plasma atrial natriuretic peptide, renin, angiotensin II and aldosterone under different conditions of sodium intake in rats

It is known that atrial natriuretic peptide [ANP] plays a major role in the homeostasis of body fluids. There are evidence that ANP may link the heart, kidney, adrenal, blood vessels and brain in a complex system involved in the regulation of body fluids and electrolytes as well as blood pressure. The study was carried out on 90 male albino rats divided into 6 groups, each of 15 rats. The first group was kept for 15 days on normal diet [controls], the 2nd, 3rd groups were kept on different sodium intake, 50, 150 and 350 nmol/kg of diet respectively. The 5th group was injected daily with 0.01 micro l/kg body weight ANP and the last group was injected daily with 0.02 micro l/kg body weight cafedrine HC1, theodrenaline HC1 for 7 days. At the end of the experiments the animals were sacrificed, blood samples were obtained and plasma separated and kept frozen for analysis. The results show that plasma ANP, renin, aldosterone and angiotensin II were significantly decreased in the 3rd, and 4th groups while in the 2nd group there was no statistically significant change when compared with controls. After injection of cafedrine, HC1, theodrenaline HC1, plasma ANP was significantly decreased while plasma renin, aldosterone and angiotensin II were significantly increased. After injection of ANP, significant decrease in renin and aldosterone was observed but angiotensin II showed significant decrease. Plasma sodium and potassium concentrations were significantly increased in all cases compared to controls. The results were discussed according to current literatures