Effect of cortisone treatment on the active transport of calcium by the small intestine

Abstract

A B S T R A C T It is generally recognized that glucocorticoid administration may diminish calcium absorption in vivo as well as the active transport of calcium by the intestine in vitro. Recent studies by others have emphasized the possibility of an alteration in the metabolism of vitamin D to 25-hydroxycholecalciferol in accounting for the steroid effects on calcium absorption. The results obtained in the present studies fail to support this hypothesis.The present studies confirm that the administration of cortisone or other glucocorticoids to the rat interferes with the active transport of calcium by duodenal gut sacs in vitro. This abnormality is not due to an alteration in the permeability of the intestine to calcium, and it cannot be corrected by the administration of either massive doses of vitamin D3 or modest doses of 25-hydroxycholecalciferol. Experiments concerned with the effects of cortisone on the level of the vitamin D-dependent duodenal calcium-binding protein, the amount of bioassayable vitamin D activity in the mucosa, and the distribution and metabolism of 'H-vitamin D3, did not provide evidence in favor of a hormone-related defect in either the localization of vitamin D or its metabolism to 25-hydroxycholecalciferol. Alterations in the transport of iron and D-galactose, not dependent on vitamin D, suggest that cortisone treatment may be responsible for more than a simple antagonism to the effects of vitamin D.The results of the present studies indicate that cortisone administration affects the cellular mechanisms mediating calcium transport in a manner that is opposite to the

Effect of glucocorticoids on vitamin D metabolism

“…The inability of these investigators to show a stimulatory effect of glucocorticoids on the conversion rate of (25-0H)Ds to (1,25-0H)rDs is possibly due to severely D-deficient animals used in their studies. This explanation is supported by our findings as well as by their own observations in vitamin D-supplemented animals, in which the levels of CaBP and bioassayable vitamin D activity in intestinal mucosa from cortisone-treated animals were higher than control animals [20]. A number of studies in vitamin D-supplemented or moderately vitamin D-deficient animals indicates that glucocorticoids may cause an enhanced production of (1,25-OH)2Ds despite the observed inhibition of intestinal calcium absorption [25-281.…”

“…This evidence seems to be in conflict with the well documented inhibitory effect of glucocorticoids on intestinal calcium absorption [ 18,191. However, this inhibitory effect is only seen with pharmacological doses of steroids and takes days to develop [20], while the stimulation of the lo-hydroxylase activity is demonstrated with moderate doses of glucocorticoids within a matter of hours.…”

Effects of Menatetrenone on the Decrease in Calcium Balance Induced by Vitamin K-Deficient Diet and Sodium Loading in Rats.

“…MK-4 has been shown to inhibit bone resorption in a mouse calvaria culture system (22) and en hance the mineralization of osteoblasts in a human cell culture system (23). It is well known that calcium absorp tion from the intestine decreases in ovariectomized rats (24) and in rats that have been treated with steroids (25). In this study, the reduction in calcium balance tended to induce the decrease in bone density, suggesting that cal cium balance plays an important role in bone metabo lism.…”

Relationship of glucocorticoid dosage to serum bone gla‐protein concentration in patients with rheumatologic disorders

“…Increased bone resorption has been attributed to secondary hyperparathyroidism resulting from glucocorticoid inhibition of gastrointestinal calcium absorption (6)(7)(8) and increased urinary calcium loss (9). Other investigators (10,l I) have been unable to find an increase in serum immunoreactive parathyroid hormone (iPTH) and postulate that there may be increased bone sensitivity to iPTH.…”