HYDRALAZINE DILATES LARGE EPICARDIAL CORONARY-ARTERIES IN CONSCIOUS DOGS THROUGH AN ENDOTHELIUM-INDEPENDENT MECHANISM

In chronically instrumented conscious dogs, hydralazine (30-300 mu g/kg) and nitroglycerin (NTG 0.03-10 mu g/kg) dose-dependently dilated large epicardial coronary arteries. Simultaneously, hydralazine also dose-dependently dilated small coronary arteries, whereas a similar effect was observed only after NTG >0.3 mu g/kg. When large coronary arteries were deendothelialized by a balloon angioplasty catheter, dilation of large coronary arteries in response to acetylcholine (ACh 0.3 mu g/kg) and to reactive hyperemia was reduced by 87 and 95%, respectively. In contrast, vasodilation of large coronary arteries induced by hydralazine and NTG was only minimally and similarly affected (-19% for both drugs). These findings demonstrate that in vivo hydralazine-induced dilation of large coronary arteries is endothelium independent.