Effects of lipolytic and antilipolytic agents on glycerol and free fatty acid release from isolated adipocytes of normal and diabetic rats.

Isolated adipocytes from severely diabetic rats exhibited hypersensitivity to epinephrine at low concentrations (0.05-0.1 microM) on lipolysis, compared with isolated adipocytes from normal and mildly diabetic rats. Hypersensitivity to dibutyryl cyclic AMP and theophylline at concentrations from 0.05 to 0.50 mM was not observed in adipocytes of severely diabetic rats. Insulin could not exert an inhibitory effect on epinephrine-induced lipolysis in adipocytes of severely diabetic rats. In isolated adipocytes from normal rats, hyperosmolarity due to the combination of 50 mM glucose and 100 mM sodium chloride only had an inhibitory effect on 0.25 microM epinephrine-induced lipolysis. Ten mM beta-hydroxybutyrate did not inhibit lipolysis caused by epinephrine although any lipolysis stimulated by epinephrine, dibutyryl cyclic AMP and theophylline was inhibited by insulin. Our present findings may partly explain insulin resistance in the severely diabetic state and the pathogenesis of the absence of ketosis in hyperglycemic hyperosmolar conditions.