482 INTESTINAL MATURATION; EFFECT OF PREDNISOLONE ON CALCIUM TRANSPORT

Abstract

In the adult rat intestine, absorption of calcium (Ca) is decreased by administration of prednisolone in vitro but not in vivo. In suckling rats, serum corticol levels are low and intestinal absorption of calcium high, this provided an opportunity to investigate the effect of glucocorticoids in vivo. Test (T) rats were injected with methylprednisolone, 5 mg/kg/day for 5 days prior to the studies and control (C) rats with the solvent. The jejunum + ileum of anesthetized suckling (S) 14-15 day, weanling (W) 21-22 day and adolescent (A) 42 day old, T and C rats were perfused with isotonic NaCl solution containing CaCl₂(3.4 mmoles/1), tracer ⁴⁵Ca, and Phenol Red (20 mg/1). Net absorption of calcium (NA of Ca) was measured under steady state conditions. Lumen to mucosa (LM) flux of Ca was estimated from absorption of ⁴⁵Ca. In C rats, NA of Ca (umoles/hr/g. dry wt.) decreased significantly (p < 0.01) with age (Mean ± S.E.; S, 23 ± 4; W, 14 ± 2; A, 2 ± 1). In T rats, NA of Ca was similar in S and W but significantly lower in A rats (S, 13 ± 3; W, 12 ± 1, A, 2 ± 1). The LM fluxes in C rats were: S, 53 ± 5; W, 26 ± 4; A, 7 ± 1; and in T rats: 23 ± 3, 20 ± 2 and 7 ± 1. Thus, administration of methylprednisolone significantly reduced the NA of Ca and the LM flux in S but not in W or A rats. These results suggested that prednisolone decreased the permeability of the small intestine to Ca in S but not in W or A rats. This effect could be mediated through a Vitamin D-independent mechanism.

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