Bromocryptine treatment increases lipolysis and steady-state levels of G proteins in adipocytes from lactating rats

Abstract

An increase in the rate of lipogenesis and a decrease in the lipolytic response to catecholamines can be observed in adipocytes after weaning or litter removal. Bromocryptine treatment of lactating rats also produces an increase in lipogenesis but fails to decrease the lipolytic response of adipocytes to catecholamines seen after weaning or litter removal. No changes in total number or affinity of β-adrenergic receptors or adenosine A 1 receptors were detected by bromocryptine treatment using radioligand binding assays. However, we observed an increase in the amount of radioactivity from [ 32P]NAD + incorporated into α-G s (192 ± 26%) and α-G i (178 ± 33%) by cholera- and pertussis-toxin-catalyzed ADP-ribosylation, respectively, with the same treatment. Immunoblotting using RM/1 and AS/7 antisera, which specifically recognize α-G s and α-G i1,2, respectively, confirmed the increase in the steady-state levels of these G-protein α-subunits. The increase in the steady-state levels of α-G s may account, at least in part, for the increased lipolytic response of adipocytes to catecholamines in bromocryptine-treated rats.