Abstract P116: Induction of Human Endothelin-1 Overexpression for 3 Months Increases Plasma Aldosterone

Background: The mechanisms of blood pressure (BP) regulation by endothelin (ET)-1 produced by endothelial cells are complex and remain unclear. Long-term exposure to endothelial human ET-1 overexpression causes sustained blood pressure elevation via ETA receptors. ET-1 has been shown to stimulate the release of aldosterone from the adrenal cortex. Whether aldosterone plays a role in ET-1 endothelium overexpression-induced BP elevation is still unknown. Methods and Results: Nine to 12-week-old male ieET-1 mice and control ieCre mice expressing a tamoxifen-inducible Cre recombinase (CreER T2 ) under the control of EC-specific Tie2 promoter, were treated with tamoxifen (1 mg/kg/day, SC) for 5 days and studied 3 months later. Plasma aldosterone level measured by ELISA was higher in ieET-1 compared with ieCre mice (1.21±0.14 vs. 0.70±0.09 ng/mL, P Scnn1a ), TSC22 domain family member 3 ( Rsc22d3 ), serum- and glucocorticoid-induced kinase 1 ( Sgk1 ), and ET type A and B receptors in the kidney or adrenal glands. The mRNA expression of aldosterone synthase ( Cyp11b2 , fold change: 0.52±0.06 vs 1.00±0.16, P Hsd3b1) and 6 (Hsd3b6) or steroidogenic acute regulatory protein ( Star ), were decreased in the adrenal cortex of ieET-1 compared with ieCre mice. CYP11B2 and HSD3B1 protein levels measured by Western Blotting were unchanged. Treatment of ieET-1 mice with MR antagonist eplerenone (100 mg/kg per day) during the last 2 weeks decreased systolic BP more during the day (128±2 vs. 134±3 mm Hg) than during the night (137±2 vs. 140±2 mm Hg) compared to untreated ieET-1 mice. Conclusions: These results showed that aldosterone contributes at least in part to the BP elevation caused by endothelial human ET-1 overexpression.