Effect of pertussis toxin on A1-receptor-mediated inhibition of insulin secretion

Previous studies have provided evidence for the presence on B cell membrane of adenosine receptors (P1-purinoceptors) of the A1-subtype which inhibit insulin secretion. In this work we have investigated the implication of a guanosine triphosphate (GTP) binding protein (G protein) in the A1 purinoceptor-induced inhibition of insulin secretion from the isolated perfused pancreas of the rat. A group of rats was treated with pertussis toxin (10 micrograms kg-1, i.v.) 28 h prior to pancreas extirpation. This treatment totally abolished the 50% decrease in insulin secretion induced by (+)-N6-phenylisopropyl adenosine (1.65 microM), a P1-purinoceptor agonist. These results indicate that the A1-receptor-mediated inhibition of insulin secretion involves a pertussis toxin-sensitive G protein.