Upregulation of kidney adenylate cyclase in the egg-laying hen: role of estrogen
Forte, L.R.; Langeluttig, S.G.; Biellier, H.V.; Poelling, R.E.; Magliola, L.; Thomas, M.L.
American Journal of Physiology 245(3): E273-E280
1983
ISSN/ISBN: 0002-9513 PMID: 6311026 Document Number: 215099
The kidney plays a prominent role in the physiological adaptation that occurs in mineral homeostasis during the egg-laying cycle of birds. The development of renal adenylate cyclase and parathyroid hormone (PTH) receptor characteristics in male and female chickens was studied to test the hypothesis that renal responsiveness to PTH may exhibit adaptive changes associated with reproduction that may be mediated by estrogen. Female chickens had significant increases in plasma total Ca, P and Mg by 18 wk of age, and egg laying began at 20 wk of age. Adenylate cyclase activity in the presence of PTH, forskolin or fluoride was significantly increased by 16 wk of age in the plasma membranes prepared from female chicken kidney compared with the activity of male kidney. However, the adenylate cyclase activity of renal membranes was further increased to a much greater extent after the onset of egg laying and remained elevated in egg-laying hens compared with either age-matched males or immature females throughout the period studied (109 wk of age). In egg-laying birds the density of PTH receptor sites in renal plasma membranes was increased 2-fold in the hen relative to the male, while the Kd was unchanged (2-3 nM). Treatment of male birds for 2 wk with estradiol mimicked the increases in renal adenylase cyclase activity and PTH receptor density observed in the egg-laying hen. A single dose of 15 mg estradiol/kg in 5-wk-old male birds produced a rapid increase in the PTH-dependent, forskolin-stimulated and fluoride-stimulated adenylate cyclase activities of renal membranes by 12 h, and a maximal response to the sex steroid was observed by 24 h. The kidney PTH-dependent adenylate cyclase system is regulated by endogenous estrogen in a manner consistent with upregulation of both receptor sites and catalytic subunit activity. This adaptation of the kidneys' response to PTH may be an important physiological mechanism in the maintenance of Ca and P homeostasis during the reproductive cycle of the domestic hen.