Ion transport by heart mitochondria. IX. Induction of the energy-linked uptake of K+ by zinc ion.

The accumulation of K+ by isolated heart mitochondria suspended in isotonic sucrose is markedly stimulated by the addition of Zn++. The accumulation requires a source of energy, the presence of a permeant anion such as acetate, and the presence of either inorganic phosphate or arsenate. The reaction is inhibited and reversed by uncouplers of oxidative phosphorylation and by anaerobiosis. It is also inhibited by Mg++ and Na+ ions and by ethylenediaminetetraacetate and other Zn++ chelators. The Z&+-dependent accumulation is accompanied by increased respiration and extensive reversible swelling of the mitochondria. The extent of the observed swelling and the time course of swelling are dependent on the concentration of K+ and of Znf+. In the absence of added K+, Zn+Sinduces a rapid energy-linked expulsion of the endogenous K+ of the mitochondrion. These studies indicate that the addition of Zn++ under carefully defmed experimental conditions is sufficient to induce the transport of Kf by heart mitochondria. This transport of K+ closely resembles that reported by other investigators in the presence of valinomycin, gramicidin, and parathyroid hormone.