Indirect Evidence against a Contribution of the Guanine Nucleotide-Binding Inhibitory Component of Adenylate Cyclase to Impaired Lipolysis in the Epididymal Adipose Tissue of Congenitally Obese (ob/ob) Mice

Summary

The mixed adrenergic agonist epinephrine, at a 10 μM concentration, stimulated cyclic AMP production and glycerol release in the epididymal adipose tissue of ob/ob male mice. These effects when tested, respectively, after 7 min in the presence and after 60 min in the absence of theophylline were, however, 7- and 5-fold lower than in lean controls. The alpha-adrenergic blocker phentolamine and adenosine deaminase (which destroys extracellular adenosine) did not restore a normal lipolytic response to epinephrine in the adipose tissue of ob/ob mice. These data provide indirect evidence against a hyperactive mechanism in the coupling of alpha-adrenergic receptors and adenosine receptors to N_i, the guanine nucleotide-binding inhibitory component of adenylate cyclase, as the cause of reduced lipolysis in the adipose tissue of ob/ob mice.

Key-Words:

ob/ob Mice - Cyclic AMP - Guanine Nucleotide Regulatory Protein N_i - Glycerol Release - Epinephrine - Alpha-Adrenergic Receptors - Adenosine Receptors - Adipose Tissue