Local Aldosterone Plays A Role In Aortic Endothelial Nitric Oxide Synthase Expression Of High-salt-induced Hypertensive Rats

Objective To observe the changes of eNOS in aortic in the development of high-salt-induced hypertension and investigate its possible mechanisms. Methods 100 young male Wistar rats of 50-60g were randomly selected 30 as the Control group (Control group) given ordinary powdered diet, and the remaining were given 5% high-salt powdered diet, all ras were given free drinking water. After 12 weeks, the high blood pressure rats given 5% high-salt powdered diet were randomly divided into high salt group (HS group) and high salt+eplerenone group (Eplerenone group, Epl group). Starting from 13 weeks, Epl group was given eplerenone 40mg/kg/d for 4 weeks, Control group and HS group were given the same dose of saline for 4 weeks. Systolic blood pressure was measured by tail-cuff. Rats were killed after 16 weeks. Aortic tissue was separated, then preserved at -70℃. The content of aldosterone in aortic tissue was measured by ELISA kit. The levels of mineralocorticoid receptor (MR) and endothelial nitric oxide synthase (eNOS) protein expression in aortic tissue were determined by western blotting. The NOS activity in aorta was measured by colorimetric assay. Results ①Blood pressure began to increase by 5% high-salt diet after 8w. Compared with the Control group in 12w, systolic blood pressure was more than 20mmHg, and then showed a gradual increasing trend.②Compared with the Control group in 16w, systolic blood pressure in HS group significantly increased (129.23±2.11mmHg vs 97.57±1.07mmHg, P<0.05). Blood pressure in Epl group significantly decreased after treated with eplerenone for 4 weeks (124.80±1.75mmHg vs 108.53±1.62mmHg,P<0.05), but was still higher than the Control group (108.53±1.62mmHg vs 97.57±1.07mmHg, P< 0.05). ③Compared with the Control group, the aldosterone content in aortic tissue significantly increased in HS group and Epl group (14.75±1.85 pg/mgprot> 13.28±2.36pg/mgprot vs 6.42±0.93pg/mgprot,P<0.05) and the levels of MR in aortic tissue also significantly increased in HS group and Epl group (P<0.05). ④Compared with the Control group, the eNOS protein level significantly reduced in HS group (P<0.05) and the NOS activity significantly reduced in HS group (0.49±0.05U/mgprot vs 0.66±0.07U/mgprot,P<0.05). Compared with HS group, the eNOS protein level significantly restored in Epl group(P<0.05) and the NOS activity also significantly restored in Epl group (0.67±0.07U/mgprot vs 0.49±0.05U/mgprot, P<0.05). Compared with the Control group, the eNOS protein level significantly increased in Epl group(P<0.05). Conclusion ①Systolic blood pressure significantly increases after young Wistar rats given 5% high salt diet, which can be successfully replicated high salt hypertensive rat model.②Local aldosterone and MR-mediated signaling pathways may reduce aortic eNOS protein level and activity after high salt intake. ③MR blocker Eplerenone therapy can restore the eNOS protein level and activity and improve eNOS function, which plays a role of protecting endothelial function.