The Dependence of Brain Mitochondrial Respiration on Potassium Ion*

Abstract

Brain mitochondria differed from mitochondria from other tissues (e.g., liver, kidney and heart mitochondria) in showing an increased rate of state 3 respiration in media containing high concentrations of potassium ions. The potassium-stimulated respiration of brain mitochondria increased remarkably with cither glutamate or succinate as substrate but followed a different course with the two substrates. The respiratory rate with succinate reached a maximum at about 50 mM of potassium ions, while with glutamate the maximum was reached with higher concentrations (about 100 mM) of potassium ions. Similar stimulatory effects of potassium ions were observed on respiration activated by 2, 4-dinitrophenol. In addition, potassium ions were found to compete with magnesium ions in the stimulation of state 3 respiration with NAD-linked substrates. From these results, it was suggested that potassium ions exert a direct stimulatory effect on the electron transport system.