Calcium transporter 1 and epithelial calcium channel messenger ribonucleic acid are differentially regulated by 1,25 dihydroxyvitamin D3 in the intestine and kidney of mice

We examined the expression of calcium transporter 1 (CaT1) and epithelial calcium channel ( ECaC) mRNA in the duodenum and kidney of mice. Intestinal CaT1 mRNA level increased 30-fold at weaning, coincident with the induction of calbindin-D-9k expression. In contrast, renal CaT1 and ECaC mRNA expression was equal until weaning when ECaC mRNA is induced and CaT1 mRNA levels fall 70%. Long- and short-term adaptation to changes in dietary calcium (Ca) level and 1,25 dihydroxyvitamin D-3 [1,25(OH)(2)D-3] injection strongly regulated duodenal calbindin D-9k and CaT1 mRNA. Following a single dose of 1,25(OH)(2)D-3, induction of CaT1 mRNA occurred preceded the induction of intestinal Ca absorption (significantly increased at 6 h, peak at 9 h). Neither renal CaT1 nor ECaC mRNA were strongly regulated by dietary calcium level or 1,25(OH)(2)D-3 injection. Our data indicate that CaT1 and ECaC mRNA levels are differentially regulated by 1,25(OH)(2)D-3 in kidney and intestine and that there may be a specialized role for CaT1 in kidney in fetal and neonatal development. The rapid induction of intestinal CaT1 mRNA expression by 1,25(OH)(2)D-3, and the marked induction at weaning, suggest that CaT1 is critical for 1,25(OH)(2)D-3-mediated intestinal Ca absorption.