“…Interestingly, incubation of turkey erythrocytes with 10-4M-isoproterenol results in a loss of both catecholamine-stimulated adenylate cyclase and GTPase activities but no decrease in receptor binding. GTPase activities sensitive to prostaglandin El (Bitonti et al, 1980), secretin and pancreozyminrelated peptides (Lambert et al, 1979) and glucagon (Kimura & Shimada, 1980) have now been observed in membranes from human mononuclear cells, rat pancreas and rat liver, respectively. In the case of the membranes from mononuclear cells (Bitonti et al, 1980), there is an apparently poor correlation Vol.…”