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.