Pregnancy modifies the α2-β-adrenergic receptor functional balance in rabbit fat cells

The sympathetic nervous system controls lipolysis in fat by activation of four adrenergic receptors: β1, β2, β3, and α2. During pregnancy, maternal metabolism presents anabolic and catabolic phases, characterized by modifications of fat responsiveness to catecholamines. The contributions of the four adrenergic receptors to adipocyte responsiveness during pregnancy have never been studied. Our aim was to evaluate the influence of pregnancy on adrenergic receptor-mediated lipolysis in rabbit white adipocytes. Functional studies were performed using subtype-selective and non-selective adrenergic receptor agonists. Overall adrenergic responsiveness was measured with the physiological agonist epinephrine. Non-adrenergic agents were used to evaluate different steps of the lipolytic cascade. The α2- and β1/β2-adrenergic receptor numbers were determined with selective radioligands. Non-adrenergic agents revealed that pregnancy induced an intracytoplasmic modification of the lipolytic cascade in inguinal but not in retroperitoneal adipocytes. Pregnancy induced an increase in β1- and specially β3-mediated lipolysis. The amounts of adipocyte β1/β2- and α2-adrenergic receptors were increased in pregnant rabbits. Epinephrine effects revealed an increased contribution of α2-adrenergic receptor-mediated antilipolysis in adipocytes from pregnant rabbits. These results indicate that pregnancy regulates adipocyte responsiveness to catecholamines mainly via the α2- and β3-adrenergic pathways. Pregnancy induces an intracytoplasmic modification of the lipolytic cascade, probably via hormone-sensitive lipase, with differences according to fat location.—Bousquet-Mélou, A., C. Muñoz, J. Galitzky, M. Berlan, and M. Lafontan. Pregnancy modifies the α2-β-adrenergic receptor functional balance in rabbit fat cells. J. Lipid Res. 1999. 40: 267–274.

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