EFFECTS ON CYP27 MESSENGER-RNA EXPRESSION IN RAT-KIDNEY AND LIVER BY 1-ALPHA,25-DIHYDROXYVITAMIN D-3, A SUPPRESSOR OF RENAL 25-HYDROXYVITAMIN D-3 1-ALPHA-HYDROXYLASE ACTIVITY

The production of 1 alpha,25-dihydroxyvitamin D-3 is known to be down regulated by 1 alpha,25-dihydroxyvitamin D-3 itself. It was recently shown that liver mitochondrial sterol 27-hydroxylase CYP27, present also in kidney, catalyzes 1 alpha-hydroxylation of 25-hydroxyvitamin D-3. Treatment of vitamin D-deficient rats with a single i.v, dose of 1 alpha,25-dihydroxyvitamin D-3 resulted in a marked suppression of CYP27 mRNA in kidney. The effects were not as pronounced as for CYP24. Liver CYP27 was not affected to the same extent. The results of the present communication indicate a coordinate regulation of CYP27 mRNA levels and 25-hydroxyvitamin D-3 1 alpha-hydroxylase activity by 1 alpha,25-dihydroxyvitalnin D-3 in rat kidney. (C) 1995 Academic Press, Inc.