AJP - Endocrinology and Metabolism, Vol 259, Issue 3 E370-E377, Copyright © 1990 by American Physiological Society
Regulation of plasma calcium and phosphate in calcitonin-infused rats
S. Lausson, P. Tracqui, L. Toubiana, G. Milhaud, A. M. Perault-Staub and J. F. Staub
Unite de Recherche Associee 174, Centre National de la Recherche Scientifique, Faculte de Medecine Saint-Antoine, Paris, France.
The effects of long-term constant infusion of moderate doses (2-32 ng/h) of
salmon calcitonin (sCT) on plasma Ca (and its radionuclide 45Ca), Pi, Mg,
and on endogenous rat CT (rCT) metabolism were investigated in the rat.
Daily variations were included. 1) The plasma concentrations of Ca and Pi
fell and that of Mg increased transiently during infusion, with the
duration of responses (1-3 days) depending on the sCT dose. Rats infused
with 8 ng/h sCT remained sensitive to CT after 7 and 14 days, as indicated
by the effects of minipump removal and of a bolus injection of exogenous
sCT on plasma mineral concentrations. 2) In contrast to control rats, the
well-established daily variations in plasma Ca and Pi levels were no longer
observed after 7 and 14 days of sCT infusion (8 ng/h), but normal
variations persisted for plasma Mg, circulating rCT, rCT mRNA, and rCT
thyroid content. 3) Statistical analysis of plasma mineral data, collected
at five sequential times during days 7 and 14, showed that the means were
not significantly different and that the daily variations were essentially
identical on days 7 and 14 in control rats. In contrast, the variability of
measurements for plasma Ca and Pi, but not for Mg, increased significantly
between days 7 and 14 in infused rats, and the mean differences were
significantly lower in infused rats on day 7 than in control rats. These
results are consistent with a transitory loss of the daily variations for
Ca and Pi (day 7) and the later (day 14) spontaneous recovery of some
variations in these parameters, although the individuals remain
unsynchronized.(ABSTRACT TRUNCATED AT 250 WORDS)
