Chronic 17 beta-estradiol augments relaxant role of basal nitric oxide in blood vessels from rats with heart failure

The effects of chronic 17 beta-estradiol on endothelium-dependent relaxatio n to acetylcholine (ACh) and contraction to NG-nitro-L-arginine methyl este r (L-NAME), and endothelium-independent relaxation to sodium nitroprusside (SNP) were examined on blood vessels from rats with chronic heart failure ( CHF). Two groups of ovariectomized female (50-60 days) rats were implanted with pellets containing 17 beta-estradiol(25 mu g/day) or vehicle, and give n ligation of the left main coronary artery 1 week later. Another group of ovariectomized rats was implanted with vehicle pellets, and sham-operated. After 7 weeks, thoracic aortic rings, pulmonary artery rings, and portal ve in strips were prepared for in vitro studies. Relative to sham-operated rat s treated with the vehicle, vessels from vehicle-treated, coronary-ligated rats had similar relaxation to ACh and SNP but reduced response to L-NAME t hat was significant (P<0.05) for the aorta and portal vein but not pulmonar y artery. Treatment of ligated rats with 17 beta-estradiol augmented respon ses to L-NAME in the aorta, pulmonary artery and portal Vein to values abov e those in sham-operated rat. 17 beta-Estradiol did not affect relaxation o f any vessels to SNP and increased maximum relaxation to ACh only in the po rtal vein. Hence, 17 beta-estradiol enhances the relaxant role of basal nit ric oxide in CHF.