In Vivo Intestinal Calcium Absorption in Infant Rats: Influence of Methylprednisolone and Vitamin D

The influence pharmacological doses of methylprednisolone and vitamin D on in vivo absorption of calcium from the small intestine was studied in suckling (14- to 15-day-old), weanling (21- to 22-day-old) and adolescent (42-day-old) rats. Intramuscular injection of methylprednisolone (2.5 mg/100 g body weight daily for 5 days) suppressed absorption of calcium from the jejunum + ileum of the suckling rats only. Both lumen-to-mucosa and mucosa-to-lumen fluxes of calcium were lower in the treated than in the control suckling rats, indicating that the permeability of the mucosal membrane to calcium was decreased with injection of methylprednisolone. This suggested an effect on a passive process of calcium transport rather than on the vitamin D-dependent mechanism of calcium absorption. This effect is compatable with findings of other studies showing that, in glucocorticoid treated rats, the metabolism of vitamin D is not altered in a way to decrease absorption of calcium from the small intestine. Oral administration of vitamin D (5000 IU/100 g body weight daily for 3 days) to suckling and weanling rats, did not enhance the in vivo absorption of calcium in the small intestine, an observation similar to our previous in vivo study in adolescent rats.