Effects of K + channel openers on the vascular actions of human gamma globulin

The aim of this study was to determine if the stimulatory action of human gamma globulin on the spontaneous activity of the rat mesenteric portal vein is due to decreased K + conductance. Glibenclamide potentiated the action of human γ-globulin on the portal vein by 45% and on its own had a concentration- and time-dependent biphasic (increase followed by a decrease) effect on the spontaneous activity of the portal vein. Diazoxide and pinacidil both inhibited the action of human γ-globulin on the rat mesenteric portal vein. Levcromakalim (BRL 38227) potentiated the stimulatory action of human γ-globulin on the integrated force of the spontaneous contractions of the rat mesenteric portal vein by 40% and 49% at concentrations of 0.5 and 5 μM, respectively. These studies suggest that human γ-globulin can act by directly modulating a K + channel.