ISSN:
1432-1424
Keywords:
K+ and Cl− channels
;
ion transport
;
gastric secretion
;
apical membranes
;
(H++K+)-ATPase
;
oxyntic cell stimulation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary This study concerns the properties of rapid K+ and Cl transport pathways that are present in the (H++K+)-ATPase membrane from stimulated, and secreting, gastric oxyntic cells. Ion permeabilities in the isolated stimulation-associated vesicles were monitored via the rates of H+ efflux under conditions of exclusive H+/K+ counterflux or H+−Cl co-efflux, as well as by comparison of equilibration rates for86Rb and36Cl under conditions of equilibrium exchange and unidirectional salt flux. These latter studies suggest that Rb+ and Cl pathways are conductive and independent. In spite of the functional independence of the ion pathways, several divalent cations inhibit Rb+ and Cl isotopic exchange as well as the H+ efflux that is dependent on either K+ or anion (Cl, SCN, NO2) fluxes. Zn2+ is the more potent inhibitor, reducing by 50% the sensitive component of K+, Cl, and NO2 fluxes at about 20 μm; Mn2+ has a similar effect at 200 μm. Ni2+ and Co2+ were roughly equipotent to Mn2+ while Mg2+ and Ca2+ had not inhibitory effect. These results suggest that the stimulation-induced permeabilities, while functioning independently, may be physically linked, i.e., residing within a single entity. In similar studies carried out in (H++K+)-ATPase vesicles obtained from nonstimulated cells, no vestiges of sensitivity to the inhibitory divalent cations could be detected. The implications of these findings for the physiology of the oxyntic cell in the context of a model for membrane fusion are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01868700
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