Identification of calbindin D-9k mRNA and its regulation by 1,25-dihydroxyvitamin D3 in Caco-2 cells

We have identified and quantified specific mRNAs in the human colonic carcinoma cell line Caco-2 by reverse transcriptase-polymerase chain reaction. Initial examination revealed that like rat duodenal mucosa, Caco-2 cells possessed mRNA for the vitamin D receptor. Using primers for human calbindin we found a 237-bp PCR product in Caco-2 cell RNA, but not from rat duodenal RNA. Primers for rat calbindin did not amplify calbindin mRNA in Caco-2 RNA, confirming a high degree of mismatch between rat and human sequences. 1,25(OH)2 vitamin D3 treatment (10 nM) significantly elevated calbindin mRNA levels 50% by 12 h, with maximal levels occurring by 48 h (fivefold elevation). Increasing concentrations of 1,25(OH)2 vitamin D3 (from 15 pM to 100 nM) caused progressive increases in calbindin mRNA levels following 48 h of treatment. Elevated calbindin mRNA levels were associated with enhancement of transcellular calcium transport. Our results are the first demonstration of vitamin D-regulated calbindin mRNA in a human intestinal cell line.