Role of carbon monoxide in heme-induced vasodilation

We investigated the effects of carbon monoxide and heme-L-lysinate on the diameter of isolated, pressurized gracilis muscle arterioles. Both agents increased arteriolar diameter. The vasodilatory effect of heme-L-lysinate, but not of carbon monoxide was prevented by an inhibitor of heme oxygenase. Hence, heme-L-lysinate-induced vasodilation appears to be mediated by a product of vascular heme metabolism, presumably carbon monoxide. This implies that vascular formation of carbon monoxide may subserve a vasodilatory function.