Upregulation of brain APJ receptor expression induced by high salt in pressure overload rats / 中国药理学通报

Aim To observe the effect of high salt stress on sympathetic nerve activity and brain Apelin and APJ system in pressure overload rats.Methods The suprarenal abdominal aorta was banded in male SD rats to create the pressure overload model.Four weeks later,the rats were fed a high-salt (8%NaCl)diet or a regular-salt (0.3% NaCl)diet for 1 week,and the hemodynamic changes of the rats were recorded.Sym-pathetic activity was evaluated by measuring 24 h uri-nary norepinephrine (NE)by ELISA.Real-time RCR and Western blot method were used to analyze the Ape-lin and APJ expression in the paraventricular nucleus of rats.In another protocol,ML22 1 or benzamil was intracerebroventricularly infused in the aorta banding rats fed with high-salt,and levels of 24 h urinary NE and cardiac index were recorded.In addition,normal SD rats were intracerebroventricularly infused with Na+-rich aCSF for 1 week,and the changes of blood pressure,24 h urine-NE and APJ expression levels were detected.Results In the pressure overload rats fed with high salt diet for 1 week,the mean arterial blood pressure (MAP),heart rate (HR),left ventric-ular end systolic pressure (LVESP),24 h urinary NE and APJ mRNA protein expression in paraventricular nuclear were significantly increased compared with those in control groups (P<0.05 ).However,the he-modynamics,24 h urinary NE and APJ expression showed no significant change in the sham rats fed a high salt diet.In addition,ICV infusion of APJ recep-tor antagonist ML221 or the ENaC antagonist benzamil significantly inhibited the 24 h urinary NE level and HW/BW ratio in the pressure overload rats fed high salt diet (P <0.01 ).Intracerebroventricular infusion of high Na+aCSF for 1 week in normotensive rats also significantly increased the MAP,HR,urinary-NE lev-els and brain APJ expression (P <0.0 1 ).Conclu-sions High salt increases the sympathetic nerve activ-ity in rats with pressure overload model, which is closely related to the brain APJ receptor expression and Na+sensitivity.Brain APJ receptor may be an impor-tant target in the development of salt sensitivity.

Effect of inhibiting brain reactive oxygen species on sympathetic nerve activity in DOCA-salt hypertensive rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate whether brain reactive oxygen species mediate sympathoexcitation and arterial pressure elevation in DOCA-salt hypertensive rats.</p><p><b>METHODS</b>DOCA-salt hypertensive model was established in male SD rats by subcutaneous injection of DOCA after uninephrectomy and drinking 1% NaCl solution for 4 weeks. The baseline mean arterial pressure (MAP), heart rate (HR) and renal sympathetic nerve activity (RSNA) were recorded in the rats under mild anesthesia, and MAP changes following intravenous hexamethonium injection were observed. The responses of MAP, HR and RSNA to intracerebroventricular administration of tempol (20 µmol/L in 10 µl) were evaluated; plasma NE level was measured with ELISA, and ROS level and NAD(P)H oxidase activity in the hypothalamus were detected using chemiluminescence assay.</p><p><b>RESULTS</b>MAP and plasma NE levels were significantly increased in DOCA-salt rats as compared with those in the control group (P<0.01). In DOCA-salt hypertensive rats, intravenous hexamethonium injection induced a blood pressure reduction 240% of that in control rats, and significantly increased the levels of superoxide anion and NAD(P)H oxidase activity in the hypothalamus. Intracerebroventricular microinjection of tempol also resulted in more significant changes of MAP, HR and RSNA in DOCA-salt rats than in the control group (P<0.01).</p><p><b>CONCLUSION</b>Sympathoexcitation due to increased NAD(P)H oxidase-derived ROS levels in the hypothalamus may mediate arterial pressure elevation in DOCA-salt hypertensive rats.</p>

Angiotensin 1-7 attenuates left ventricular remodeling in deoxycorticosterone acetate salt hypertensive rats / 中国药理学通报

Aim To investigate the effect of angioten-sin 1-7 (Ang 1-7 )on the cardiac hypertrophy and my-ocardial fibrosis in deoxycorticosterone acetate (DOCA)-salt hypertensive rats and its possible mecha-nism.Methods Male Sprague-Dawley rats were used to establish DOCA-salt hypertensive model,which un-derwent uninephrectomy surgery and were subcutane-ously injected with a DOCA,and replaced drinking water with 1% saline solution for 4 weeks.DOCA-salt animals were implanted with osmotic minipumps, which delivered Ang 1-7 chronically for 4 weeks (200 ng ·kg-1 ·min-1 ).Arterial blood pressure,left ven-tricular function in rats,the area of myocardial cells in HE stained specimens,and the area of myocardial fi-brosis Sirius red staining specimens were measured. Real time PCR was used to detect the expression of at-rial natriuretic factor (ANF ) and β-myosin heavy chain (β-MHC)mRNA in heart,and TGF-β1 protein expression was observed by Western blot in myocardial tissue.Results In the first week,DOCA salt rat had a significant increase in arterial blood pressure,and reached a peak in the fourth week;while the left ven-tricular end-systolic pressure (LVESP),left ventricu-lar end-diastolic pressure (LVEDP ) and ventricular contraction the maximum rate of pressure rise (+dp/dt)had also undergone significant changes in DOCA salt rats. After chronic infusion of Ang 1-7 for 4 weeks,the arterial pressure,LVESP and LVEDP were significantly reduced and +dp/dt were increased sig-nificantly in DOCA salt rats (P<0.05 ,n=7 ).Ang 1-7 significantly reduced the cardiac index and myocar-dial cell area,as well as the up-regulated expression of ANF and β-MHC mRNA in DOCA salt rats (P <0.05 ,n =7 ).Meanwhile,Ang 1-7 also significantly decreased the perivascular fibrosis and interstitial fibro-sis area, and significantly inhibited the increase of TGF-β1 expression in DOCA salt rats (P<0.05 ,n=7 ).Conclusion These results indicate that Ang 1-7 has a cardioprotective effects through reducing arterial pressure and improving cardiac fibrosis and hypertro-phy in the DOCA-salt model of hypertension.