Prolactin Receptors in Mouse Liver: Species Differences in Response to Estrogenic Stimulation

Abstract

Serum PRL [prolactin] and hepatic PRL receptors were measured in intact and OVX [ovariectomized] mice and OVX mice given several doses of EB [estradiol benzoate]. OVX significantly increased PRL binding in the liver of female mice, and EB reduced receptors to intact or below intact levels. Estrogen decreases PRL receptors in the liver of female mice. This is a striking contrast to the stimulatory effect of estrogen on hepatic PRL receptors in male and female rats. EB elevated serum PRL in OVX mice, but since other investigators reported that PRL does not alter hepatic PRL receptors in female mice, estrogen apparently reduced PRL binding sites by a direct effect on the liver. An indirect effect cannot be excluded. In male mice, estrogen increased PRL receptors in the liver as in male rats. Important species differences between female rats and female mice in estrogenic control of hepatic PRL receptors were demonstrated. The inhibitory effect of estrogen in female mice, and its stimulatory action in male mice, and its stimulatory action in male mice, suggest that the response of hepatic PRL receptors to estrogen may be sex dependent in different species. The mechanisms of action by which these effects are mediated remain to be clarified.