AJP - Renal Physiology, Vol 233, Issue 2 138-F144, Copyright © 1977 by American Physiological Society
Renal excretion of phosphate and calcium in parathyroidectomized starlings
N. B. Clark and R. F. Wideman Jr
Renal excretion patterns of calcium, phosphate, sodium, and potassium were
studied in parathyroidectomized (PTX) and parathyroid extract
(PTE)-injected PTX starlings. Sturnus vulgaris. Anesthetized birds
(Equi-Thesin or Dial) were infused intravenously with 2.5% mannitol
containing [14C]inulin. PTX caused significant hypocalcemia,
hyperphosphatemia, increased relative calcium clearance (CCa/CIn), and
decreased relative clearances of phosphate and potassium, but did not
change the clearance of sodium. Glomerular filtration rate (GFR=CIn) and
urine flow remained unchanged up to 2 h after PTX. PTE administration 3 h
after PTX returned serum calcium and phosphate values to control levels and
caused a transient (10-min) increase in GFR. Following PTE, the relative
clearances of phosphate, sodium- and potassium increased, while that of
calcium decreased significantly relative to the PTX levels. PTE caused net
tubular secretion of phosphate, decreased tubular reabsorption of sodium
and potassium (sometimes potassium secretion), and a return of excretion of
calcium to control levels. These studies indicate that the parathyroid role
in calcium and phosphate homeostasis in starlings is predominantly on the
kidney.
