Expression of angiotensin I-converting enzyme in the human gastric HGT-1 cell line

We have previously shown that angiotensin I-converting enzyme (ACE) was expressed by epithelial cells of the rabbit gastric mucosa. In a search to obtain a cell model to study the regulation of ACE expression of gastric origin and its relationship with gastrin-cholecystokinin peptides, which have been proposed as ACE substrates, we investigated whether 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 130-140 kDa whose enzymatic and immunological properties were identical to those of ACE. More than 80% of ACE activity was found to be ectoenzymatic. However, immunocytochemical localization has mainly shown an intracellular localization, suggesting that most of intracytoplasmic ACE was not enzymatically active. In addition, Northern-blot analysis and polymerase chain reaction showed that the mRNA encoding that protein displayed a size and a sequence identical to those of somatic ACE. It therefore appears that the HGT-1 cell line could be a useful model to study both the regulation of gastric ACE and its interactions with gastrin-cholecystokinin peptides.