valinomycin and benzylamine

Isolated gastric glands made permeable with digitonin treatment were employed to study the ionic requirements of acid formation. Acid formation was monitored by the accumulation of a novel weak base probe, [14C]benzylamine. ATP-dependent acid formation was found to require K+ in a concentration-dependent manner, with an apparent K0.5 = 7 mM. The anion dependence of acid formation gave a selectivity sequence of Cl = I greater than Br greater than NO3 greater than SO4 = isethionate, with isethionate being approximately 50% as effective as Cl. The dependence of acid formation on [Cl] gave an apparent K0.5 = 6 mM. Addition of the K+ ionophore, valinomycin, to resting glands (cimetidine pretreatment) resulted in a two- to threefold increase in ATP-dependent acid formation. In contrast, stimulated (forskolin pretreated) glands showed a greater accumulation of benzylamine with ATP but significantly less valinomycin stimulation. The valinomycin stimulation required both K+ and Cl- and was inhibited by omeprazole and Sch 28080. The results are interpreted to indicate that major events in the transition from a resting to a stimulated state include changes in both K+ and anion permeability of the secretory membrane of parietal cells.

Topics: Animals; Anions; Benzylamines; Cations, Monovalent; Cell Membrane Permeability; Gastric Acid; Gastric Mucosa; In Vitro Techniques; Kinetics; Male; Potassium; Rabbits; Reference Values; Valinomycin