Energy-dependent efflux of K+ from heart mitochondria. |
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Authors: | E Chavez D W Jung G P Brierley |
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Affiliation: | Department of Physiological Chemistry, Ohio State University Columbus, Ohio 43210, USA |
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Abstract: | The efflux of 42K+ from the matrix of isolated heart mitochondria under conditions of steady state K+ has the properties of an energy-linked exchange reaction. Efflux requires respiration and external K+, is sensitive to uncouplers and to Mg+2, and is markedly decreased by oxidative phosphorylation. Efflux is stimulated by Pi and by mersalyl, but declines under conditions which promote net uptake of K+ and acetate. Acetate strongly inhibits efflux in the presence of mersalyl. These data suggest that mitochondrial K+ levels are not maintained by a balance between inward K+ pumping and a passive outward leak, but rather that a nearly constant K+ pool results from a regulated interplay between an inward K+ uniport (responsive to membrane potential) and a exchanger (responsive to the transmembrane pH gradient). |
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