PROPOFOL-ASSOCIATED DILATION OF RAT DISTAL CORONARY-ARTERIES IS MEDIATED BY MULTIPLE SUBSTANCES, INCLUDING ENDOTHELIUM-DERIVED NITRIC-OXIDE

Previous in vitro studies on the effect of propofol on coronary arteries have shown variable results, ranging from constriction to no effect to dilation. Although most of these studies reported that the observed effect is endothelium-independent, propofol also releases nitric oxide from cultured porcine endothelial cells. The present study examines the direct effect of propofol in rat distal coronary arteries in vitro, especially in regard to endothelial dependence and involvement of the adenosine triphosphate (ATP)-sensitive potassium channels (K-ATP channels). For ty-three subepicardial arteries (size 91.1+/-15.8 mu m) from Wistar rats were studied in vitro in a no-flow, pressurized (40 mm Hg) state, using an optical density video detection system. After preconstriction with the thromboxane analog U466191 mu M, relaxation responses to increasing concentrations of propofol (10(-6) 10(-4) M) were measured after 1) endothelial denudation, 2) pretreatment with the nitric oxide synthase inhibitor N-G-nitro-L-arginine (L-NNA), 3) pretreatment with the cyclooxygenase inhibitor indomethacin, 4) pretreatment with the K-ATP channel blocker glibenclamide, or 5) no intervention (control). Propofol produced a significant concentration-dependent vasodilation of the U46619-preconstricted coronary arteries. This effect was significantly attenuated by endothelial denudation, pretreatment with L-NNA, or indomethacin, but was not affected by glibenclamide. We conclude that propofol has a direct vasodilatory effect on distal coronary arteries in rats. This effect is primarily endothelium-dependent and is mediated by multiple substances, including nitric oxide (NO) and a vasodilatory prostanoid. The effect is not mediated by opening of the K-ATP channels.