Regulation by various hormones and agents of adenosine-3′,5′-monophosphate levels in islets of langerhans of rats

Abstract

Regulation by various hormones and agents of adenosine-3′,5′-monophosphatc (cyclic AMP) levels in intact islets of rat pancreas was studied, employing either the prelabeling technique or the protein kinase catalytic method. Many agents were found to increase islet cyclic AMP levels. These include corticotropin, glucagon, isoproterenol, prostaglandins (E 1, E 2, A 1, and F 1), secretin, thyroid-stimulating hormone, β-adrencrgic agonists, tolbutamide and GTP. Epinephrine caused a slight decrease in islet cyclic AMP level, but in the presence of z-adrenergic blockers, they conversely increased the cyclic AMP levels. Isoproterenol, on the other hand, increased cyclic AMP levels and its effect was abolished by β-adrenergic blocking agents. The evidence presented further substantiates the contention that in rat islet plasma membranes there exist both α- and β-ardenergic receptors and that cyclic AMP levels in islets are closely modulated by α- and β-adrenergic receptor activation.