The aim of the present report was to study the effect of ischemia-repe
rfusion on the endothelial cell function of coronary vessels. Twelve a
dult male dogs were instrumented for the measurement of aortic and lef
t ventricular pressures, heart rate and coronary blood flow. The left
anterior descending coronary artery was occluded for 90 minutes follow
ed by 20 minutes of reperfusion. Acetylcholine was infused into the co
ronary artery at a rate of 15 mu g/kg/min. Coronary flow, heart rate a
nd aortic and left ventricular pressures were registered during the pr
e-occlusion period and after 20 minutes of reperfusion under basal con
ditions, as well as during acetylcholine administration. These same pa
rameters were also measured during reactive hyperemia following vessel
deocclusion. Acetylcholine produced a 155 % increasing coronary flow
during the pre-occlusion period (p < 0.05). In the reperfusion period,
no statistically significant difference was observed between the flow
s in the presence and absence of this substance, nor were there any di
fferences in the other cardiovascular parameters monitored. Triphenylt
etrazolium staining confirmed myocardial infarction in all the hearts
examined. The authors conclude that reperfusion following myocardial i
nfarction prevents the increasing in coronary flow in response to acet
ylcholine as a result of endothelial dysfunction in the resistance cor
onary vessels.