ROLES OF HEME OXYGENASE CARBON-MONOXIDE SYSTEM IN GENETICALLY HYPERTENSIVE RATS

Although carbon monoxide (GO) has been suggested to be involved in the regulation of cardiovascular function through activation of soluble g uanylyl cyclase, the pathophysiological significance in hypertension r emains unknown We therefore examined the effects of heme oxygenase (HO ) inhibitor zinc protoporphyrin IX (ZnPP-IX) on blood pressure and det ermined HO mRNA expression level in various tissues in stroke-prone sp ontaneously hypertensive rats (SHR-SP/Izm) and Wistar Kyoto rats (WKY/ Izm). Although ZnPP-IX significantly increased systolic blood pressure in both strains, the increment of blood pressure was larger in SHR-SP /Izm than in WKY/Izm. An essentially similar increase of blood pressur e was demonstrated even in the ganglion blocker-pretreated rats, Const itutive type HO-2 mRNA levels in the aorta and kidney and inducible ty pe HO-1 mRNA levels in the cardiac ventricle were significantly increa sed in SHR-SP/Izm compared with WKY/Izm. Clearly these results indicat e the importance of the endogenous HO/CO system in the peripheral tiss ues in genetically hypertensive rats, (C) 1997 Academic Press.