Effects of estrone and estradiol-17β on 25-hydroxycholecalciferol hydroxylase activities in female Japanese quail

Abstract

Equimolar amounts of estrone and estradiol-17β injected into sexually immature female Japanese quail caused comparable increases and decreases in the renal activity of 25-hydroxycholecalciferol (25HCC) 1α-hydroxylase and 25-hydroxycholecalciferol 24-hydroxylase, respectively. Peak activity of the former enzyme was induced by both estrogens within 6 hr and had declined by 24 hr. Plasma concentrations of estrone and estradiol following the injection were maximal within 3–6 hr of injecting the steroid i.m. Following [ 3H]estradiol injection, 25% of the radioactivity was located with estrone in the plasma following separation by TLC. Conversely, following [ 3H]estrone injection 30% of the radioactivity in plasma was located with estradiol. Thus, both estrone and estradiol may have physiological effects in quail, which in part may be due to their in vivo interconversion. Evidence that prolactin may be mediating the estrogenic stimulation of the 25HCC 1α-hydroxylase is also presented.