AJP - Endocrinology and Metabolism, Vol 242, Issue 3 146-E153, Copyright © 1982 by American Physiological Society
Influence of parathyroid state on calcium uptake in bone
G. J. Lemon, J. B. Bassingthwaighte and P. J. Kelly
The exchange of calcium and strontium ions in bone was studied in control
dogs, dogs made hypocalcemic by parathyroidectomy, and dogs rendered
hypercalcemic by injection of parathyroid hormone. After injections of
tracer into the tibial nutrient artery, extraction of tracer during
transcapillary passage was measured and expressed as a fraction of 1.
Extraction over the first 3 min in normal dogs was 0.46 +/- 0.09 (n = 6),
in hypocalcemic dogs it was increased to 0.53 +/- 0.07 (n = 6), and in
hypercalcemic dogs it was decreased to 0.39 +/- 0.07 (n = 5). Subsequent
washout was less rapid than normal in hypoparathyroid dogs and more rapid
than normal in hyperparathyroid dogs. We conclude from this that the
immediate volume of distribution in bone (or the number of available
binding sites) for strontium diminishes as the parathyroid hormone level
increases.
