INFLUENCE OF ESTROGENIC STATUS ON THE LIPOLYTIC-ACTIVITY OF PARAMETRIAL ADIPOSE-TISSUE IN-VIVO - AN IN-SITU MICRODIALYSIS STUDY

Ovarian hormones have been shown to modulate the metabolism of adipose cells obtained from adipose tissue of different animals. The aim of t his study was to better understand the short- and long-term influences of estrogens on the in vivo lipolytic response of rat parametrial fat pads, determined by measurement of extracellular glycerol concentrati ons using in situ microdialysis. Possible direct effects of estrogens on lipolysis were studied by perfusion of a potent estrogenic analogue such as moxestrol. Moxestrol (10(-6) M) failed to increase glycerol c oncentrations in estrus, diestrus, or 8-day ovariectomized animals. Ho wever, the basal glycerol concentrations and the Lipolytic responses s timulated by 10(-6) M isoproterenol were decreased in parametrial fat pads of diestrus, compared with estrus, rats. Greater decreases in bas al and stimulated glycerol concentrations were observed in rats that h ad been ovariectomized for 8, 15, or 30 days. Ln ovariectomized rats, isoproterenol-induced lipolysis was restored to the levels observed in diestrus animals by a daily injection of 17 beta-estradiol for a peri od of? days. These results implicate estrogens as long-term modulators of in vivo basal and stimulated lipolytic responses of rat parametria l fat pad.