AJP - Renal Physiology, Vol 245, Issue 3 345-F348, Copyright © 1983 by American Physiological Society
Calcitonin decreases the renal tubular capacity for phosphate reabsorption
R. K. Zalups and F. G. Knox
The effects of pharmacologic doses of synthetic salmon calcitonin on the
renal tubular capacity of phosphate (Pi) transport were determined in the
presence and absence of maximally phosphaturic doses of parathyroid hormone
(PTH). Thyroparathyroidectomized rats were given graded infusions of Pi (1,
2, and 3 mumol/min) to prevent the hypophosphatemic effects of calcitonin
and to determine the maximum transport of Pi for the kidney (TmPi/GFR). The
maximum transport of Pi for the rats treated with calcitonin was 2.46 +/-
0.27 mumol/ml. This value was significantly less than that of 3.88 +/- 0.32
mumol/ml (P less than 0.05) for the control animals but was significantly
greater than the maximum transport of Pi of 1.16 +/- 0.05 mumol/ml (P less
than 0.05) for the rats treated with PTH. Furthermore, there was no
significant difference between the maximum transport of Pi for the rats
treated with PTH and that of 1.04 +/- 0.05 mumol/ml for the rats treated
with PTH plus calcitonin. We conclude that pharmacologic doses of
calcitonin decrease the tubular capacity for Pi reabsorption of the kidney
and that the effect is significantly smaller than that of maximally
phosphaturic doses of PTH.
