Endocrinology, Vol 117, 2267-2273, Copyright © 1985 by Endocrine Society
The effects of chronic prednisone administration on intestinal receptors for 1,25-dihydroxyvitamin D3 in the dog
AB Korkor, J Kuchibotla, M Arrieh, RW Gray and WA Gleason Jr
Glucocorticoid inhibits intestinal calcium absorption. To further explore
the mechanism of this inhibition, we studied dogs during the administration
of oral prednisone (1.2-1.5 mg/kg X day) for 20 to 28 weeks in comparison
to untreated dogs. Prednisone administration had no effect on serum
25-hydroxyvitamin D concentrations, but was accompanied by a fall in serum
1,25-dihydroxyvitamin D [1,25-(OH)2D] concentrations from 87 +/- 20 pM
(control) to 62 +/- 28 pM (prednisone-treated; P less than 0.01). Cytosol
prepared from the duodenal, jejunal, and ileal mucosa of control dogs was
found to contain a specific 3.2S [3H]1,25- (OH)2D3 binder analogous to the
binder that has been observed in the intestine of other species and in
other tissues. The apparent concentration of this binder decreased
progressively from duodenum to ileum. Prednisone administration increased
the apparent duodenal concentration of the binder from 170 +/- 91 (control)
to 363 +/- 124 fmol/mg protein (prednisone-treated; P less than 0.025). The
intestinal content of calcium-binding protein also declined progressively
from the duodenum to the ileum, but was not affected by prednisone
administration. These data suggest that events other than alterations in
intestinal 1,25-(OH)2D3 receptors must mediate the inhibition of intestinal
calcium absorption during chronic glucocorticoid administration.
