FOOD-INTAKE AND ESTRADIOL EFFECTS ON INSULIN BINDING IN BRAIN AND LIVER

Three groups of ovariectomized rats were treated for 6 days: 1) estrad iol benzoate (100 mug/kg) (SC) and fed ad lib; 2) vehicle-injected con trols fed the same amount of food as eaten by estradiol-treated rats; 3) vehicle-injected, free-feeding controls. Specific binding of insuli n to liver and hypothalamus slices was measured by quantitative film a utoradiography. Estradiol-treated rats lost weight (p < 0.001) and had elevated plasma insulin (p < 0.01). Liver insulin binding in rats wit h estradiol treatment was greater (p < 0.01) than in rats without estr adiol, but was less (p < 0.05) than in controls fed the same food leve ls as consumed by the estradiol-treated rats. Therefore, with equal fo od intake, estradiol decreased liver insulin binding. Insulin binding in the dorsomedial, ventromedial, and arcuate nuclei of the hypothalam us was unchanged by food intake or estradiol, however. Thus, altered i nsulin binding in the arcuate, ventromedial, or dorsomedial nuclei of the hypothalamus is probably not involved in the effects of insulin or estradiol on food intake.