VANADATE CAUSES SYNTHESIS OF ENDOTHELIUM-DERIVED NO VIA PERTUSSIS-TOXIN-SENSITIVE G-PROTEIN IN PIGS

The effects of sodium orthovanadate, an inhibitor of protein tyrosine phosphatases, on the endothelial nitric oxide (NO) pathway were studie d in vitro. Vanadate caused endothelium-dependent relaxations in isola ted porcine coronary arteries, which were abolished by N-w-nitro-L-arg inine methyl ester. The relaxations were also abolished by pertussis t oxin, an inhibitor of certain G proteins. Tyrosine kinase inhibitors, genistein and yano-3-ethoxy-4-hydroxy-5-phenyl-methylcinnamamide (ST-6 38), significantly attenuated the vanadate-induced relaxations. Vanada te also caused pertussis toxin-sensitive, endothelium-dependent relaxa tions in isolated porcine renal and femoral arteries and jugular veins . Immunoblots, using an antibody to phosphotyrosines and to c-Src in n ative porcine aortic endothelial cells, respectively, showed that vana date induced an elevation of phosphotyrosine proteins and a decrease i n the amount of the active form of c-Src family kinases; both changes were markedly suppressed by cotreatment with ST-638. These results ind icate that in porcine blood vessels, vanadate causes a synthesis of en dothelium-derived NO for which endothelial tyrosine kinases and pertus sis toxin-sensitive G protein are considered to be closely involved.