Pepsin secretion by the totally isolated, vascularly perfused rat stomach

The gastric pepsin output by the totally isolated, vagally denervated, and both luminally and vascularly perfused rat stomach was studied. Basal release of pepsin was 3% of total gastric mucosal stores per hour. Topical (luminal) administration of 0.001 M HCl was without effect. Graded concentrations of pentagastrin, gastrin, histamine, and impromidine in the vascular perfusate were tested. Pentagastrin induced only a slight increase in pepsin release (15% of total content per hour). Gastrin had a more pronounced effect and elicited a significant increase in the pepsin output, reaching a maximum of 28% of total pepsin content per hour. The CD50 of gastrin was 0.061 nM. Histamine and impromidine likewise produced significant increases in the pepsin secretion (maximum, 40% and 35% of total stores per hour, respectively). When the CD50 of histamine (0.718 microM) was compared with that of impromidine (0.011 microM), impromidine on molar basis had 65 times higher potency than histamine as a pepsin secretagogue. When the pepsin and acid responses during gastrin, histamine, and impromidine stimulation were compared, the pepsinogen secretion was shifted to the left and thus was more sensitive to stimulation than the acid secretion.