Cyclic AMP, adenylate cyclase and cyclic AMP-phosphodiesterase activities in diabetic rat adipocytes

The effect of streptozotocin-induced diabetes on cyclic AMP content, adenylate cyclase and cyclic-AMP phosphodiesterase activities in rat adipocytes was investigated. The results show that diabetes induced an increase in intracellular cyclic AMP. Basal adenylate cyclase activity and in response to norepinephrine were higher in fat cell membranes from diabetic rats. Adenylate cyclase activity stimulated by fluoride was the same in both normal and diabetic preparations. Low and high Km phosphodiesterase activities in adipocytes from diabetic rats were higher than the controls. The results suggest that the deficiency of insulin present in the diabetic state induces an increase in adenylate cyclase activity which increases the cyclic AMP production. This increase in cyclic AMP promotes a higher cyclic AMP-phosphodiesterase activity which is not sufficient to hydrolyze all the newly formed cyclic AMP.