title: Free radicals inhibit endothelium-dependent dilation in the coronary resistance bed.
abstract: Oxygen free radicals contribute significantly to ischemia-reperfusion myocardial damage in vivo. We studied the effect of reactive products of O2 generated by electrolysis of the saline perfusate on coronary vasomotor tone and endothelium-mediated vasodilator responsiveness in 41 isolated rabbit hearts. Under constant flow conditions, electrolysis induced a progressive increase in perfusion pressure associated with a modest reduction in myocardial contractile function. The responses to the endothelium-independent vasodilators papaverine and adenosine tended to be increased by 1.5- to 2-fold, indicating that the increase in perfusion pressure was due, at least in part, to increased resistance vessel tone. However, resistance vessel dilations to the endothelium-dependent agents acetylcholine and serotonin were markedly reduced. Various degrees of protection against increases in perfusion pressure and inhibition of endothelium-dependent dilation during electrolysis were obtained with catalase, a scavenger of hydrogen peroxide; superoxide dismutase, a scavenger of superoxide; and desferrioxamine, which chelates iron and thereby inhibits hydroxyl radical production. Furthermore the action of nitroprusside, a direct-acting stimulator of soluble guanylate cyclase, was not diminished during the electrolytic treatment. We conclude that inhibition of endothelium-dependent dilation is a prominent action of reactive products of O2 in the coronary resistance bed. In combination with a free radical-induced increase in resistance vessel tone this might limit recovery of myocardial perfusion post ischemia.
authors.affiliation: Institute of Applied Physiology, University of Freiburg, Federal Republic of Germany.
authors.forename: D J
authors.initials: DJ
authors.lastname: Stewart
authors.forename: U
authors.initials: U
authors.lastname: Pohl
authors.forename: E
authors.initials: E
authors.lastname: Bassenge
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D002374:Catalase / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D003676:Deferoxamine / Q000494:pharmacology; D004572:Electrolysis; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005609:Free Radicals; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D010208:Papaverine / Q000494:pharmacology; D010477:Perfusion; D011817:Rabbits; D012701:Serotonin / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D005609:Free Radicals; D012701:Serotonin; D010208:Papaverine; D002374:Catalase; D013482:Superoxide Dismutase; D003676:Deferoxamine; D000241:Adenosine; D000109:Acetylcholine