AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 1 41-R50, Copyright © 1986 by American Physiological Society
Renal excretion in gull chicks: effect of parathyroid hormone and calcium loading
N. B. Clark and L. L. Mok
Renal clearance experiments were performed on herring gull (Larus
argentatus) and great black-backed gull chicks (L. marinus) to test the
importance of parathyroid hormone (PTH), parathyroidectomy (PTX), and
calcium loading on excretion patterns of sodium, potassium, calcium, and
phosphate. PTX reduced the relative clearance of phosphate to near zero
within 2 h. Conversely, PTH stimulated net secretion of phosphate within 40
min. Calcium loading caused a drop in phosphate excretion identical to that
of PTX, presumably by inhibiting PTH secretion by the parathyroid glands.
This also could be reversed by administration of PTH. Serum phosphate
values were highest in PTX gulls and lowest in calcium-loaded gulls. The
relative clearance of calcium (CCa/CIn) was elevated in calcium-loaded
birds. However, CCa/CIn did not change significantly in response to either
PTX or PTH in the sham-operated or PTX birds. Serum calcium values were
highest in calcium-loaded gulls and lowest in PTX gulls, the reciprocal of
the effects on serum phosphate.
