Zych W, Dołowy K, Ostrowski J
Department of Gastroenterology, Medical Center of Postgraduate Education, Warszawa, Poland.
J Physiol Pharmacol. 1993 Sep;44(3):283-92.
The aim of this study was to determine pepsinogen secretion by isolated rat chief cells in relation to changes of membrane potential obtained by the use of potassium ionophore valinomycin and different extracellular K+ concentrations, or protonophore carbonyl cyanide m-chlorophenyl hydrazone (CCCP) at different pH. While valinomycin or CCCP decreased basal and cAMP-stimulated secretory response of the chief cells, they increased secretion of pepsinogen stimulated by calcium ionophore A23187. When Ca2+ was absent from the incubation media, A23187-stimulated secretion of pepsinogen significantly decreased. Moreover, the omission extracellular calcium reversed the potentiating effects of valinomycin or CCCP on A23187-stimulated secretory response. It is known that pepsinogen secretion is a biphasic process. In the first phase, Ca2+ is released from its intracellular stores, while the second one depends on extracellular calcium entering the cell. Our results suggest that this phase is dependent also on membrane potential.
