AUTORADIOGRAPHIC IDENTIFICATION OF A GASTRIN RECEPTOR ON THE HUMAN PARIETAL-CELL

Gastrin plays an important role in regulating gastric acid secretion a nd gastrointestinal mucosal growth but its cellular sites of action in man have not been determined. Using cryostat sections of gastric muco sal tissue we have identified (I-125-gastrin binding followed by fixat ion-wet emulsion autoradiography) and characterized (I-125-gastrin bin ding followed by counting) a gastrin receptor binding site in the huma n stomach. This site displayed binding characteristics similar to thos e observed in isolated cell systems: specifically, I-125-gastrin bindi ng was rapid (t(1/2) similar to 10 min at 37 degrees C), temperature-d ependent (3.5 fold more radioligand bound at 22 degrees C than at 4 de grees C) and saturable. The binding of the radioligand was also tissue specific and was five-fold greater in the gastric body than in the ga stric antrum and duodenum. In the autoradiographs, silver grains were localized only to parietal cells and not to other epithelial cell type s. In the presence of 40 nM gastrin grains were no longer present over parietal cells demonstrating that these sites were both saturable and of high affinity. These data provide the first demonstration of gastr in binding sites (putative receptors) on parietal cells in the human s tomach and suggest that gastrin acts directly on these cells to help r egulate gastric acid secretion and/or mucosal growth. (C) 1998 Elsevie r Science B.V.