PMID: 6169721Oct 25, 1981Paper

On the relationship between the uncoupler-induced efflux of K+ from heart mitochondria and the oxidation-reduction state of pyridine nucleotides.

The Journal of Biological Chemistry
D W Jung, G P Brierley

Abstract

Respiring heart mitochondria exchange matrix 42K+ with extramitochondrial K+ at a rapid rate in the presence of Pi (Chávez, E., Jung, D. W., and Brierley, G. P. (1977) Arch. Biochem. Biophys. 183, 460-470, 1977). This exchange reaction is strongly inhibited by uncouplers. However, under two rather similar sets of conditions, the addition of an uncoupler results in a rapid, transient increase in the exchange of matrix 42K+ with external K+ when the mitochondria are suspended in KCl or, alternatively, in a net loss of matrix 42K+ from mitochondria suspended in K+-free media. These conditions are: (a) the addition of an uncoupler to respiring mitochondria after the accumulation of a small amount of phosphate salt, and (b) the presence of a Ca2+-chelator or ruthenium red with uncoupler. Loss of 42K+ under these conditions occurs with all substrates tested, is completely blocked by rotenone, and is accompanied by an almost complete oxidation of both NADH and NADPH. In the presence of rotenone and acetoacetate, only NADH is oxidized and 42K+ efflux does not occur. It is concluded that simply dissipating the mitochondrial protonmotive force by addition of an uncoupler is not sufficient to induce release of mitochondrial K+. Uncoupler-...Continue Reading

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