Gastric Acid and Pepsin-Stimulating Activity of Non-Sulphated Fragments of Gastrin in the Cat

The gastric acid and pepsin-stimulating activities of several C terminal fragments of non-sulphated human gastrin were investigated in the conscious cat prepared with cannulated gastric fistulae with a reproducible, continuous infusion method to construct dose-response curves. The gastric acid-stimulating activities were quantified by reference to the ED50 and were compared with the activity of synthetic non-sulphated human gastrin 17 (SHG17NS) and cat gastrin 17 (SCG17NS). SHG17NS had an ED50 of 0.329 nmol kg-1 h-1. SHG16NS, SHG15NS and SHG13NS all showed similar activities to SHG17NS. SCG17NS tested at low doses had similar activity to SHG17NS. SHG10NS, G5 and G4 and peptavlon showed progressively lower acid-stimulating activities: 26, 12, 9 and 9%, respectively, compared with SHG17NS. The gastric acid-stimulating activities of all the peptides were paralleled by similar pepsin-stimulating activities. The ratios of pepsin secretion:acid secretion were similar for all the peptides (1--2 microgram pepsin/microEq H+). The results are discussed in relation to the biological activity of the circulating gastrin components in the cat compared with other species and it is argued that component IV (corresponding to gastrin tetradecapeptide or minigastrin) is a major, physiologically active, circulating form of the hormone in the cat.