IDENTIFICATION OF VITAMIN-D-STIMULATED ALKALINE-PHOSPHATASE IN IEC-6 CELLS, A RAT SMALL-INTESTINE CRYPT CELL-LINE

The IEC-6 cell line was derived from newborn rat small intestinal cryp ts and maintains characteristics of nontransformed crypt epithelial ce lls. We have reported that alkaline phosphatase (ALP) activity, a diff erentiation marker for intestinal epithelial cells, is regulated in IE C-6 cells by 1,25-dihydroxycholecalciferol (1,25(OH)(2)D-3). Using rev erse transcription polymerase chain reaction, we determined that the A LP in IEC-6 cells is the liver/bone/kidney ALP (LALP) isoenzyme and no t the mature enterocyte form. Levamisole, a specific blocker for LALP, blocked the ALP activity of IEC-6 cells. Kinetic studies showed that 1,25(OH)(2)D-3 increases V-m values of ALP in IEC-6 cells while K-m va lues remain the same. Northern analysis of LALP mRNA levels in IEC-6 c ells indicated that 10(-7) M 1,25(OH)(2)D-3 acts by increasing alkalin e phosphatase activity at the gene expression level. (C) 1994 Academic Press, Inc.