Active transport of potassium by heart mitochondria

¹ Department of Physiology, Yale University School of Medicine, New Haven, Connecticut

Rabbit heart mitochondria contained potassium which could not be removed with four washings of isotonic sucrose or sodium chloride at 0–4°C. Aging, increasing concentrations of potassium, and a number of metabolic poisons either partially or completely inhibited the active transport of potassium into heart mitochondria when these particles were incubated for 15 minutes in air at 37.4° in a medium to which alpha-ketoglutarate and AMP or ATP had been added. Compounds uncoupling oxidative phosphorylation—such as arsenite, 2,4-dinitrophenol, l-thyroxine, calcium chloride, dicumarol, pentachlorophenol and methylene blue—inhibited potassium transport but usually only at relatively high concentrations (10^–3 m). With the exception of p-chloromercuribenzoate, neither aging nor metabolic inhibitors prevented the extrusion of water by the mitochondria in the presence of alpha-ketoglutarate and AMP or ATP. Although addition of either ATP or substrate alone to the mitochondrial suspension resulted in a significant increase in the potassium gradient, the latter was much greater when both substrate and ATP (or ADP or AMP) were added together. ADP or AMP alone caused a very slight but probably not significant increase in the potassium gradient and creatine phosphate had no effect.

Note:
With the Technical Assistance of Fredrick W. Klein and Patsy L. S. Smith