POTASSIUM STIMULATION OF OXIDATION AND PHOSPHORYLATION IN PIGEON-MUSCLE MITOCHONDRIA

Abstract

With alpha-ketoglutarate as substrate and a hexokinase – glucose phosphate acceptor system, the rates of oxidation and phosphorylation of pigeon-muscle mitochondria were measured in media in which the proportion of potassium to sodium was varied. As the potassium concentration was elevated from 0 to about 70 mmoles/liter, the sodium concentration was correspondingly decreased. With both the Warburg apparatus and the polarograph, the rate of respiration was shown to rise as the proportion of potassium in the medium was increased. The mean rate in the high-potassium media was 130% of that in the high-sodium media over the five-minute period measured with the oxygen electrode, and 135% over the thirty-minute period measured by Warburg manometry. The rate of phosphorylation was stimulated to an even greater extent than the rate of oxidation as sodium was replaced by potassium. In every preparation tested, the rates of phosphorylation and the P/O ratios were higher in the high-potassium media than in the high-sodium media.