A specific gastrin receptor in human gastric mucosa.

Biological active 125I-synthetic human gastrin (125I- SHG ) appeared to bind specifically on human gastric mucosal membrane preparations. Gastrin binding was reversible, saturable and of high affinity (Kd = 3.44 +/- 3.44 X 10(-10)M) with the binding site (3.66 +/- 0.34 fmol/mg protein) at 37 degrees C for 30 min (pH 7.4). Specific gastrin binding was present in the fundic mucosa and absent from the antral, duodenal, jejunal, and colonic mucosa. Gastrin analogues (tetragastrin, pentagastrin, caerulein, and synthetic human gastrin) inhibited 125I- SHG specific binding. However, the specific gastrin binding was not inhibited by glucagon, insulin, acetylcholine, atropine, histamine, or cimetidine. It was suggested that gastrin and histamine H2 receptor or gastrin and muscarinic cholinergic receptor did not share the same locus.