Mutual potentiation of combined effects of carbacholine and histamine on secretion and isozyme spectrum of pepsin from gastric mucosa cells of the frog

Pepsin secretion was studied in vivo in the primary culture of isolated secretory gastric mucosa cells of a frog (Rana ridibunda). The injection of animals with carbacholine (200 μg/100 g weight) or histamine (100 μg/100 g weight) or addition of hormones (100 μM) into the incubation medium of isolated gastric cells significantly increased pepsin activity. In vitro, preliminary addition of the specific antagonists of these hormones to the incubation medium (1 μM atropine or 100 μM cimetidine) completely suppressed the effects of hormones. The effect of histamine is season-dependent. Combined injection or simultaneous addition to incubation medium of isolated cells of carbacholine and histamine caused mutual potentiation of their effects. In this case, the quantitative response of the cells exceeded the theoretical sum of the stimulant effects of each of these two hormones alone. According to electrophoresis, the hormones cause quantitative changes in isozyme spectrum of proteolytic enzymes but do not significantly affect their qualitative characteristics.