AJP - Gastrointestinal and Liver Physiology, Vol 241, Issue 1 49-G53, Copyright © 1981 by American Physiological Society
Intestinal absorption of calcium: role of dietary phosphate and vitamin D
N. Brautbar, B. S. Levine, M. W. Walling and J. W. Coburn
The intestinal absorption of calcium (Ca) has been shown to depend on
vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], and dietary phosphorus
(P) concentration. This study was designed to evaluate the role of dietary
P independent of vitamin D3 or 1,25(OH)2D3. Vitamin D-deficient rats were
studied during dietary P restriction and were compared with control groups
raised on a normal-phosphorus diet (NP). Balance studies were sued. Net
intestinal Ca absorption was significantly lower with dietary P restriction
compared with the NP group. This malabsorption of Ca was corrected by the
administration of either D3 for 1,25(OH)2D3, despite hypophosphatemia.
Everted gut sacs showed a marked reduction in the uptake of 45Ca in the
duodenum, jejunum, and ileum during dietary P restriction. We concluded
that dietary P concentration plays a major role in intestinal Ca absorption
in the vitamin D-deficient rats. These findings suggest an effect of the
low-phosphate diet on the vitamin D-dependent, Ca-transport mechanism.
