The Effect of Prednisolone® upon the Metabolism and Action of 25-Hydroxy and 1,25-Dihydroxyvitamin D3

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RESUMO

Treatment of vitamin D-deficient rats with Prednisolone® does not alter the rate of conversion of [3H]25-hydroxyvitamin D3 to [3H]1,25-dihydroxyvitamin D3, but the further conversion of [3H]1,25-dihydroxyvitamin D3 to a more polar metabolite is more rapid in the Prednisolone®-treated animals. This more polar metabolite is biologically inactive, periodate-insensitive, and persists in the intestine as long as 1,25-dihydroxyvitamin D3. Also, the time course of action of 1,25-dihydroxyvitamin D3 upon intestinal calcium transport is altered by Prednisolone® treatment. Treatment with Prednisolone® did not change the magnitude of the initial response to 1,25-dihydroxyvitamin D3 at 7 hr, but did decrease the response at 24 and 48 hr after a single dose of 1,25-dihydroxyvitamin D3. The present results show that one of the means by which large doses of adrenal corticoids alter intestinal calcium transport is by stimulating the further metabolism of 1,25-dihydroxyvitamin D3 to a more polar, biologically inactive intestinal metabolite.

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