AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 1 295-R302, Copyright © 1994 by American Physiological Society
Renal responses to parathyroid hormone in young chickens
J. Q. Feng and N. B. Clark
Department of Medicine, University of Texas Health Science Center, San Antonio 78284.
Renal clearance studies were performed in chicks 1, 5, and 9 days after
hatching. Calcium gluconate was infused to block endogenous parathyroid
hormone (PTH) secretion, whereas ethylene glycol-bis(beta-aminoethyl
ether)-N,N,N',N'-tetraacetic acid (EGTA) was infused to stimulate
endogenous PTH secretion. PTH, dibutyryl adenosine 3',5'-cyclic
monophosphate (DBcAMP), or vehicle was administered intravenously. In
9-day-old birds, urinary cAMP and inorganic phosphate excretion fell
dramatically after calcium loading and rose significantly after PTH,
DBcAMP, or EGTA administration. These manipulations had no significant
effect on excretion of calcium or inorganic phosphate in 1-day-old
hatchlings. Five day-old-chicks gave an intermediate response. All three
age groups, as well as 15-day-embryos, showed sharp increases in urinary
cAMP values after PTH administration. Thus the adult response pattern to
PTH appears to develop gradually during the first week after hatching or to
be suppressed during the perinatal period, whereas the second-messenger
response to the hormone, indicating hormone-receptor interaction, is
present from late embryogenesis onward.
