Acute effect of estradiol on the renal vitamin D hydroxylases in Japanese quail

Abstract

It has been reported previously by us and others that in vivo estradiol administration stimulates in vitro 1,25-(OH) 2D 3 production in the Japanese quail and chicken. The present investigation was done to study the dose- and time-response relationships of estradiol-induced stimulation of in vitro 1,25-(OH) 2D 3 production. In addition, the reported permissive role of androgen in this response was studied. Four-week-old immature female Japanese quail, either primed with testosterone propionate (5 mg/kg) or without androgen priming, were injected i.m. with three different doses (0.01, 0.1 and 1.0 mg/kg) of estradiol benzoate dissolved in 95 % ethanol. One, 4,12 and 24 hr after in vivo estradiol injection, kidney homogenates were incubated with tritiated 25-(OH)D 3. The results were similar whether or not the birds were primed with androgen. Under both conditions all three doses of estradiol stimulated l,25-(OH) 2D 3, and inhibited 24,25-(OH) 2D 3, production at 12 and 24 hr with one exception (0.01 mg/kg dose at 12 hr in androgen-primed birds). At 4 hr these responses were seen only at the higher doses. The most rapid response was suppression of 24,25-(OH) 2D 3 synthesis by the 0.1 mg/kg dose of estradiol at 1 hr in the androgen-primed birds. These responses in 1,25-(OH) 2D 3 and 24,25-(OH) 2D 3 production after a single dose of estradiol may be seen prior to a detectable rise in plasma calcium.