EXPRESSION OF ANGIOTENSIN I-CONVERTING ENZYME IN THE HUMAN GASTRIC HGT-1 CELL-LINE

We have previously shown that angiotensin I-converting enzyme (ACE) wa s expressed by epithelial cells of the rabbit gastric mucosa. In a sea rch to obtain a cell model to study the regulation of ACE expression o f gastric origin and its relationship with gastrin-cholecystokinin pep tides, which have been proposed as ACE substrates, we investigated whe ther the HGT-1 human gastric cell line, which expresses gastrin, could also express ACE, using enzymatic and immunodetection methods as well as Northern-blot analysis and polymerase chain reaction. Results show that HGT-1 cells expressed a protein with a molecular weight of 130-1 40 kDa whose enzymatic and immunological properties were identical to those of ACE. More than 80% of ACE activity was found to be ectoenzyma tic. However, immunocytochemical localization has mainly shown an intr acellular localization, suggesting that most of intracytoplasmic ACE w as not enzymatically active. In addition, Northern-blot analysis and p olymerase chain reaction showed that the mRNA encoding that protein di splayed a size and a sequence identical to those of somatic ACE. It th erefore appears that the HGT-1 cell line could be a useful model to st udy both the regulation of gastric ACE and its interactions with gastr in-cholecystokinin peptides.