GLUCOCORTICOID REGULATION OF 1,25(OH)₂VITAMIN D₃RECEPTORS: DIVERGENT EFFECTS ON MOUSE AND RAT INTESTINE

Abstract

We have investigated the possibility that glucocorticoids alter responsiveness to vitamin D by regulating the 1,25(OH)2D3 receptor in rat intestine. In contrast to the mouse where glucocorticoids caused receptors to decline, rats treated with glucocorticoids showed a substantial increase ( approximately 50%) in the number of intestinal 1,25(OH)2D3 receptors. This resulted from an increase in receptor content with no change in affinity for 1,25(OH)2D3. Receptor stimulation was even greater in vitamin D-deplete rats. Moreover, adrenalectomy led to a significant decline in receptor number. Although the properties of the receptor are similar in rat and mouse intestine, the divergent response to glucocorticoids emphasizes major differences between species in the regulation of 1,25(OH)2D3 receptor number.