AJP - Gastrointestinal and Liver Physiology, Vol 255, Issue 3 313-G318, Copyright © 1988 by American Physiological Society
Stimulation of acid formation in permeable gastric glands by valinomycin
S. J. Hersey and L. Steiner
Department of Physiology, Emory University, Atlanta, Georgia 30322.
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.
