Co-operative Effects of an Inhibitor NH⁺₄ and of an Activator K⁺ on the Acid Secretory Rate in Frog Gastric Mucosa in Vitro : A Multi-Enzyme System

Abstract

Effects of concentrations of ammonium ion (NH⁺₄) and potassium ion (K⁺) in the serosal solution on the acid secretory rate by bullfrog gastric mucosa were studied at near saturating substrates concentrations in vitro. The hydrogen chloride production system was treated as a multi-enzyme system. From kinetic analyses, the system was found to have co-operativities with regard to the activator K⁺ and the inhibitor NH⁺₄. The co-operativity of the inhibitor increased as the K⁺ concentration increased. The co-operativity of K⁺ increased as the NH⁺₄ concentration increased. Considering the fact that chloride ion (Cl^-) and thiocyanate ion (SCN^-) do not have co-operativities, it was suggested that SCN^- inhibits the Cl^- transport chain reaction and that NH⁺₄ inhibits the hydrogen (H⁺) transport chain reaction. It was also discussed that NH⁺₄ and SCN^- were not uncoupler-type inhibitors like 2, 4-dinitrophenol.