Calcium Transport In Small Intestine Research Articles

Calcium transport in small intestine during early development: role of vitamin D.

To define the role of vitamin D in calcium transport in the intestine during early development, female weanling rats were placed on vitamin D-replete or vitamin D-deficient diets, grown to maturity, and mated with normal males. Pups born to vitamin D-replete and vitamin D-deficient mothers were killed at various times after parturition, and calcium transport in the small intestine as well as the concentrations of calcium and phosphate in the plasma were measured. Transport of calcium in pups from vitamin D-replete and vitamin D-deficient litters was identical at 3 and 14 days postpartum but was threefold greater in pups from vitamin D-replete litters at weaning and 3 wk postweaning. 1,25-dihydroxyvitamin D3 had no effect on calcium transport at 14 days postpartum but did induce transport at weaning. Plasma concentrations of calcium at 3 days postpartum were nearly normal but decreased during the suckling period from 10.3 mg/100ml to 7.2 mg/100 ml in vitamin D-deficient rats. These results suggest that calcium transport in the intestine during early development is not mediated by vitamin D but that a vitamin D-sensitive transport system develops late in the suckling period.

Calcium transport in small intestine during pregnancy and lactation.

The factors involved in calcium homeostasis during the mammalian reproductive cycle and specifically in the control of active calcium transport in the intestine have not been thoroughly investigated. For this reason calcium transport in the intestine was measured in vitamin D-replete and vitamin D-deficient rats during pregnancy and lactation using the everted gut sac technique. In addition the changes in the plasma concentrations of calcium and 1,25-dihydroxyvitamin D were measured and correlated with transport. During the later stages of pregnancy and during lactation, the concentration of calcium in the plasma is reduced 10-30%. In turn, in the vitamin D-replete rat, the concentration of 1,25-dihydroxyvitamin D in the plasma increases from a control value of 26 pg/ml to 158 pg/ml at day 14 of lactation. Calcium transport in the intestine increases late in pregnancy, peaks during lactation, and then falls to control values by 3 wk postweaning in both vitamin D-replete and D-deficient animals. These findings strengthen the established relationship between 1,25-dihydroxyvitamin D and active calcium transport in the intestine as well as suggest that some factor(s) independent of vitamin D is stimulating intestinal calcium transport during the reproductive cycle.