pH effects on oxidative phosphorylation of rat liver mitochondria.

TOBIN, RICHARD B., CARL R. MACKERER, AND MYRON A. ~EHLMAN. PH ejf’ects on oxidative phosphorylation of rat liver mitochondria. Am. J. Physiol. 223(l) : 83-88. 1972.-Respiration and oxidative phosphorylation of rat liver mitochondria were studied polarographically as functions of the pH of the incubation medium. Oxidation of pyruvate in the presence of ADP (state 3) and succinate, pyruvate, a-ketoglutarate, and ascorbate in the presence of ATP (state 4) were not affected by pH alterations. However, oxidation of succinate, ascorbate, and ar-ketoglutarate in state 3 and succinate, pyruvate, cr-ketoglutarate, and ascorbate in the presence of !2,4-dinitrophenol were pH sensitive. P/O ratios of all of the substrates were not affected by pH alterations in the range 5.9-8.0. Since there was no pH effect on pyruvate oxidation in states 3 and 4 and on P/O ratios of all tested substrates, it is concluded that the process of oxidative phosphorylation is not primarily regulated by extramitochondrial alterations in pH. Therefore, it is suggested that metabolic aberrations associated with acidosis and alkalosis are not caused by the direct effects of cytosolic pH on mitochondrial ATP synthesis.