ROLES OF ALPHA(1)-ADRENOCEPTOR ACTIVITY IN THE RELEASE OF NITRIC-OXIDE DURING ISCHEMIA OF THE CANINE HEART

The difference in end-products of the nitric oxide, i.e., nitrate-plus -nitrite, in the coronary arterial and venous blood was increased duri ng coronary hypoperfusion of the canine heart (12.8+/-0.6 vs. 2.2+/-0. 2 mu M at the baseline). Norepinephrine from sympathetic nerve endings in the heart is released due to ischemic stress, however the relation of norepinephrine with nitric oxide is unknown during ischemia. Neith er beta- or alpha(2)-adrenoceptor antagonists attenuated the release o f nitric oxide during coronary hypoperfusion. An intracoronary infusio n of an alpha(1)-adrenoceptor antagonist attenuated the release of nit ric oxide during coronary hypoperfusion (5.3+/-0.4 mu M), and the atte nuation of alpha(1)-adrenoceptor activity further decreased coronary b lood flow during hypoperfusion. These findings suggest that a(1)-adren oceptor activity contributes to the mechanisms whereby nitric oxide is released from the ischemic myocardium. (C) 1995 Academic Press,Inc.