Potentiation of forskolin-induced increase of cAMP by diamide and N-ethylmaleimide in rat pancreatic islets.

In isolated rat pancreatic islets, the effect of diamide and N-ethylmaleimide (NEM) on forskolin- as well as on glucagon-induced elevation of cAMP was studied. Forskolin and glucagon increased cAMP levels in batch-incubated islets. Diamide and NEM further augmented forskolin-induced increase of cAMP levels, whereas glucagon-stimulated elevation of cAMP was not affected. From our data it is likely that under the conditions of the present study, the thiols related to the Ns-protein and the catalytic unit are insensitive to oxidation and alkylation. The potentiation of forskolin-induced cAMP production in intact islet cells by diamide and NEM may be due to inactivation of the thiols related to the Ni-protein.