So far, no cells have been found to synthesize both of the homologous horomones, cholecystokinin and gastrin. Northern analysis and reverse transcription PCR showed, however, that the human gastric carcinoma cell line (AGS) expresses both a gastrin mRNA or 0.7 kb and a cholecystokinin transcript of 0.8 kb. A library of sequence-specific radioimmunoassays, cleavage with processing-like enzymes and chromatography subsequently revealed that the gastrin mRNA was translated into progastrin that was constitutively secreted into the medium (45 ± 3 pmol/1). Neither procholecystokinin nor any of its processing products were detectable in cells and media. The result suggest that differentiation into gastrin- or cholecystokinin-producing cells may be regulated at the translational level. The gastric cell line. AGS, provides a model for studies of translational regulation of cell differentiation.
