Succinate oxidation by human liver mitochondria

Abstract

Factors controlling the rate of oxidation of succinate were studied in mitochondria isolated from twenty-seven specimens of normal human liver obtained at operation. These were compared with mitochondria prepared from the livers of anesthetized and unanesthetized rats. Previously reported lower rates of succinate oxidation by human liver mitochondria were confirmed. This difference was no longer apparent when the succinic dehydrogenase activities of mitochondrial acetone powders were compared. The apparent Km of succinate for human liver mitochondrial succinoxidase is less than that of the anesthetized and unanesthetized rat. The concentration of oxalacetate is greater in human liver mitochondria compared with the anesthetized and unanesthetized rat. In both aerobic- and cyanide-inhibited mitochondria, the extent of the apparent succinate linked reduction of mitochondrial pyridine nucleotide was less in man than in the rat. In aerobic rat liver mitochondria, anesthesia lowers the extent of succinate-linked pyridine nucleotide reduction.