Polarographic studies of energy metabolism in rat liver homogenates

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Abstract
Oxidative phosphorylation and respiratory regulation were studied in rat liver homogenates by use of the oxygen electrode. Addition of 250 µm ADP to rat liver homogenates containing succinate, α-ketoglutarate, ß-hydroxybutyrate, or glutamate stimulated respiration 300–600%. Respiration declined sharply after the added ADP was phosphorylated. ATP, especially in the presence of MgCl2, also stimulated homogenate respiration, though much less effectively than ADP at equivalent concentrations below 1 mm. Amytal or malonate, in concentrations sufficient to depress substrate-ADP respiration, had no effect on substrate-ATP respiration. ADP:O ratios were measured and corrected for ATPase activity. Values obtained were 2.0, 4.1, and 3.0 for succinate, α-ketoglutarate, and ß-hydroxybutyrate, respectively.