RELATION OF THE METABOLISM OF PIGEON-MUSCLE MITOCHONDRIA TO THE NET UPTAKE OF POTASSIUM AND ITS SELECTION OVER SODIUM

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Abstract
Three processes (cation accumulation, rate of oxidation, and rate of phosphorylation) were measured on each of the mitochondrial preparations made from pigeon-breast muscle. Mitochondria were incubated for 30 minutes in media containing ATP, a hexokinase–glucose acceptor system, and sodium and potassium in the ratio of 1:1. Variation in metabolic rate was achieved by using α-ketoglutarate, α-ketoglutarate + muscle supernatant, malate, or β-hydroxy-butyrate as substrates. The mitochondria and the media were analyzed before and after incubation so that accurate concentration gradients could be calculated. When α-ketoglutarate was substrate, a small but highly significant net uptake of potassium and an increased potassium gradient were found. The change in sodium was statistically insignificant, showing selection of potassium over sodium. Only in β-hydroxybutyrate, where the rates of respiration and phosphorylation were low, was there a net uptake of sodium as well as potassium so that no cation selection was apparent.
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