AJP - Endocrinology and Metabolism, Vol 249, Issue 6 626-E633, Copyright © 1985 by American Physiological Society
Renal cAMP and 1,25(OH)2D3 synthesis in estrogen-treated chick embryos and hens
A. Martz, L. R. Forte and S. G. Langeluttig
Onset of sexual maturity in female chickens or administration of estrogen
to mature males or to juveniles of either sex results in increased
parathyroid hormone (PTH)-dependent adenylate cyclase activity and
increased 25-hydroxyvitamin D3-1-hydroxylase activity in kidney. The
relationship between estrogen-mediated alterations of these two enzyme
systems was investigated in embryonic and mature, egg-laying chickens
treated in vivo with 17 beta-estradiol (E2). Basal and PTH- and
forskolin-stimulated adenylate cyclase activity in kidney plasma membrane
preparations was not affected by E2 treatment of 19-day-old chick embryos
or of 41-wk-old egg-laying females. High, possibly maximal, levels of
catalytic activity in control embryos and hens may have precluded further
stimulation by E2. In contrast, E2 significantly enhanced 25-hydroxyvitamin
D3-1-hydroxylase activity of embryonic kidney up to 10-fold (P less than
0.005). In mature females, E2 caused cessation of egg laying accompanied by
a significant reduction (P less than 0.005) of 25-hydroxyvitamin
D3-1-hydroxylase activity. These results indicate that the PTH-dependent
adenylate cyclase and the 25-hydroxyvitamin D3-1-hydroxylase systems of
avian kidney can be regulated independently and suggest that factors in
addition to estrogen are involved in their regulation.
