High-affinity binding sites for gastrin on isolated rabbit gastric mucosal cells.

A biologically active gastrin analogue, [125I](Nle11)-HG-13, appears to bind specifically to saturable binding sites on isolated rabbit gastric mucosal cells: Kd = 70 pM at pH 7.4 and at 37 degrees C. Increasing incubation temperature from +4 degrees C to +37 degrees C increased specific binding. Gastrin binding was shown to be reversible and the dissociation rate was enhanced with cold gastrin. The binding sites were saturated with 0.2 fmol of labelled gastrin per 10(6) mucosal cells. Gastrin binding was not inhibited by secretin, glucagon, Met-enkephalin, physalaemin, eledoisin, BPP, VIP, carbachol, histamine, atropine or cimetidine. Gastrin analogues (HG-4, HG-8, (Leu15)-HG-17), CCK-7 and gastrin antagonists (proglumide or benzotript) inhibited [125I](Nle11)-HG-13 specific binding. We concluded that isolated cells from rabbit gastric fundic mucosa contain high-affinity binding sites for a gastrin analogue (Nle11)-HG-13.