Effect of Ionophores on Activity of Na+,Cl-(HCO 3 - )-ATPase

We studied the effects of ionophores on activity of Na+,Cl-(HCO (3) (-) )-ATPase. The most significant effect on the activity of this enzyme was produced by protonophore 2,4-dinitrophenol. The effect of this drug largely depended on the cation and anion composition and pH of the incubation medium and its pH. Activity of Na+,Cl-(HCO (3) (-) )-ATPase increased at neutral and weakly alkaline pH and decreased at pH below 6.5-6.7. In control animals (without histamine injection) with very weak or absent Na+,Cl-(HCO (3) (-) )-ATPase activity, the observed effect of the protonophore on ATPase activity was also virtually absent. The stimulatory effect of other ionophores (monensine, valinomycin, and A(23187)) was significantly weaker and depended on pH of the incubation medium, its cationic and anionic composition, and concentration of these ionophores.