Effects of estrogen on the responses of male and female rats to starvation-refeeding.

The effects of sex, castration and estrogen treatment of castrated rats subjected to starvation-refeeding were studied. Food intakes, liver lipid levels and the activities of glucose 6-phosphate dehydrogenase and malic enzyme in ad libitum-fed, starved and starved-refed rats were determined. Sex differences observed in the intact ad libitum-fed rats could be explained in part by the differences in estrogen levels. Sex differences were obliterated in the starved-refed intact rats but were observed when castrated female starved-refed rats were compared to castrated male starved-refed rats. The differences could not be erased with the administration of estrogen. Estrogen significantly reduced food intake of castrated rats. Results of this study suggest that the characteristically higher liver lipid level and enzyme activity in the female, compared to the male, may reflect the female's tendency to undereat when circulating estrogen levels are high and to compensate (by overeating) for this undereating when estrogen levels are low.