Cystic fibrosis transmembrane regulator mRNA expression relative to ion-nutrient transport in spontaneously differentiating human intestinal CaCo-2 epithelial cells.

The relative abundance of cystic fibrosis transmembrane regulator (CFTR) message at various stages of postconfluence development was compared with evolving cellular ion-nutrient transport properties of CaCo-2 human intestinal cells. Initially these cells demonstrate electrogenic Cl secretion manifested by secretagogue-induced changes in short-circuit current. Over time, however, the secretory characteristics of CaCo-2 monolayers diminish, and brush border hydrolase activities and glucose-dependent and amiloride-sensitive Na transport increase. With a polymerase chain reaction-derived cDNA probe to CFTR exon 13, two distinct mRNA transcripts of 6.5 and 4.3 kb were found. No significant differences in their abundance were noted in cells at 6 and 28 days after confluence. These data suggest two possible interpretations for the role of CFTR protein. First, if CFTR is membrane Cl channel, its protein expression or activity could be differentially regulated during CaCo-2 cell development. Alternatively, CFTR may not be a Cl channel but may serve as an important regulatory membrane protein.