INFLUENCE OF PROLACTIN ON IN-VIVO AND IN-VITRO LIPOLYSIS IN RABBITS

Three experiments were conducted to assess the influence of prolactin on lipolysis in rabbits. In vivo, a single injection of 1 mg of ovine prolactin induces increased plasma glycerol and nonesterified fatty ac ids concentrations within 30 min (P < 0.01). On the contrary, in vitro , oPRL did not stimulate glycerol release in isolated adipocytes at ph ysiological concentrations (under 10(-8) M). In a third experiment, th e effect of chronic hyperprolactinemia on the adrenergic control of li polysis was studied (daily subcutaneous injections of 1 mg ovine prola ctin for 12 days). The weight of perirenal adipose tissue at the end o f the period of injections was 27% lower in the prolactin-injected (PR L) rabbits than in the control (CTL) rabbits (88 +/- 15 g vs. 120 +/- 25 g; P < 0.05). Food intake during the period of injections was 28% l ower in the PRL group than in the CTL group (177 +/- 21 g/d vs. 246 +/ - 13 g/d; P < 0.05). Basal glycerol release was 157% higher in adipocy tes from PRL rabbits than in those from CTL rabbits (P < 0.05). Stimul ation of lipolysis with different adrenergic agonists was similar in b oth groups. These results suggested an indirect influence of prolactin on adipose tissue lipolysis in rabbits, but mechanisms implicated in this effect remain to be elucidated. Copyright (C) 1996 Elsevier Scien ce Inc.