Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
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The mitochondrial vitamin D3-25 hydroxylase has been identified as CYP27, a cytochrome P450 active in bile acid and vitamin D3 (D3) metabolism. The purpose of the present studies to investigate CYP27 intestinal regulation by both 25-hydroxyvitamin D3 (25OHD3) and calcitriol (1,25(OH)2D3). D depleted hypocalcemic rats were submitted to 2 distinct experimental protocols: rats were i) administered 28 pmol/d 25OHD3 by osmotic mini-pump for a period of 1 to 7 days, or ii) injected iv with 1,25(OH)2D3 at doses of 2.4 to 240 nmol/kg and killed 6h later. Duodena were taken and RNA extracted. Membranes were hybridized with a 404bp CYP27 cDNA probe . 25OHD3 administration led to a progressive decrease in CYP27 mRNA abundance over the treatment period studied with a level after 7d of 25OHD3 administration representing 46% of that observed in unsupplemented animals (r2=0.67, p < 0.001). Acute administration of 1,25(OH)2D3 also led to a dose-related decrease (p < 0.001 at doses of 120 and 240 nmol/kg). Our data indicate the presence of a significant expression of CYP27 in rat duodena. Moreover, the duodenal CYP27 was found to be significantly influenced by both 25OHD3 and 1,25(OH)2D3.

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Poster Number PAtheodoropoulos0496
Keywords: vitamin D, intestine, 25-hydroxylase