To investigate the role of endothelium-derived nitric oxide (EDNO) and adenosine in functional myocardial hyperemia, we examined the effect of N(G)-nitro-L-arginine (NNLA) and 8-p-sulfophenyl-theophyllin (8-ST) on coronary vasodilation in response to increased myocardial oxygen consumption (MVO(2)) in anesthesized dogs. NNLA significantly attenuated the increase in coronary conductance from 28±6% to 16±2% with atrial pacing, from 69±5% to 36±6% with isoproterenol and from 25±6% to 9±4% with constriction of the aorta. The combined administration of NNLA and 8-ST did not further change coronary conductance. It appears that EDNO may play an important role in functional hyperemia. EDNO and adenosine may interact to produce coronary vasodilation when MVO(2) increases.
endothelium-derived nitric oxide