Vasa vasorum in atherosclerotic coronary arteries: responses to vasoactive stimuli and regression of atherosclerosis.

The goals of this study were to determine whether vasa vasorum in atherosclerotic coronary arteries respond to vasoactive stimuli and to examine effects of regression of atherosclerosis on blood flow through vasa vasorum in coronary arteries. We studied three groups of monkeys: normal, atherosclerotic, and regression. Blood flow to vasa vasorum was measured with microspheres. Blood flow to intima-media (ml/min x 100 g) was 5 +/- 1 (mean +/- SEM) in normal and 47 +/- 7 in atherosclerotic monkeys (p less than 0.05). Infusion of phenylephrine or serotonin did not alter flow through vasa in normal monkeys. In atherosclerotic monkeys, phenylephrine decreased flow through vasa vasorum in intima-media of coronary arteries to 24 +/- 4 (p less than 0.05), and serotonin decreased flow to 27 +/- 5 (p less than 0.05). In regression monkeys, blood flow to intima-media was sixfold less (7 +/- 2 ml/min x 100 g) than in atherosclerotic monkeys (p less than 0.05). During infusion of adenosine, blood flow to vasa was fourfold greater in atherosclerotic monkeys than after regression of atherosclerosis. This finding suggests that loss of vessels, not constriction of existing vessels, accounts for the decrease in flow through vasa in intima-media after regression of atherosclerosis. We conclude that vasa vasorum in atherosclerotic coronary arteries respond to vasoconstrictor stimuli and that there is loss of vasa vasorum and a large decrease in blood flow through vasa to intima-media of coronary arteries after regression of atherosclerosis.