Cholera toxin does not impair hormonal inhibition of adenylate cyclase and concomitant stimulation of a GTPase in adipocyte membranes.

The influence of cholera toxin on hormonal inhibition of adenylate cyclase and concomitant stimulation of low Km GTPase was studied in adipocyte membrane preparations. In hamster adipocyte ghosts, cholera toxin caused an about 8-fold activation of the adenylate cyclase. The antilipolytic hormonal factors, prostaglandin E1 (1 micro M), N6-phenylisopropyladenosine (1 micro M) and nicotinic acid (30 micro M) reduced both basal and cholera toxin-stimulated enzyme activities. Similar data with regard to inhibition of cholera toxin-stimulated adenylate cyclase were obtained in mouse and rat adipocyte ghosts. As studied in hamster adipocyte ghosts, prostaglandin E1 (1 micro M) increased GTP hydrolysis by a low Km GTPase by about 3-4 fold. Pretreatment of the membrane preparation with cholera toxin did not impair prostaglandin E1-induced GTPase stimulation. The data suggest that cholera toxin does not directly affect the GTPase enzyme stimulated by adenylate cyclase inhibitory hormones.