The effects of chronic ethanol treatment on endothelium-dependent responses in rat thoracic aorta

Abstract

The purpose of this study was to investigate the effects of chronic ethanol consumption on blood pressure and vascular responses, specifically, the possible alterations in endothelium-dependent relaxation which are associated with ethanol-induced hypertension in the rat model. Male rats received ethanol in drinking water for 13 weeks. Systolic pressure was recorded weekly. Following treatment, segments of thoracic aorta with and without intact endothelium were used to generate relaxation-response curves to the endothelium-dependent agents, acetylcholine, ATP and bradykinin, as well as the endothelium-independent agents, adenosine and sodium nitroprusside. Mean systolic pressures at the end of the treatment period were: 127.8 ± 1.2 and 151.1 ± 1.3mmHg for controls and ethanol-treated rats, respectively. Ethanol treatment did not affect the relaxation produced by either acetylcholine, ATP or sodium nitroprusside in aorta with or without endothelium. In contrast, ring segments with intact endothelium from ethanol-treated rats exhibited augmented relaxation in response to both adenosine and bradykinin compared to controls. Removal of the endothelium abolished the relaxation produced by bradykinin in both groups. Although removal of the endothelium had no effect on the relaxation produced by adenosine in the control group, it attenuated the adenosine-induced relaxation in the ethanol-treated group back to control levels. These data suggest that chronic ingestion of ethanol causes elevated blood pressure and augments the endothelium-dependent relaxation to bradykinin. These findings also suggest that chronic ethanol treatment can cause the appearance of an endothelium-dependent component in the relaxation produced by adenosine. These augmented endothelium-dependent relaxations observed with chronic ethanol consumption would seem to oppose rather than contribute to hypertension that develops with chronic ethanol consumption and may serve in a protective capacity.