Effect of temperature on oxidative phosphorylation in hibernators and nonhibernators.

Abstract

The efficiencies of oxidative phosphorylation (P/O ratios) of isolated liver mitochondria from control and cold-adapted albino rats as well as aroused and torpid southeastern brown bats [Myotis a. austroriparius] were compared at 5 incubation temperatures (37, 29, 21, 13, and 5[degree]C). At 37 and 29[degree]C, the P/O ratios of all preparations were normal but appeared uncoupled at 21 and 13[degree]C with succinate as the exogenous substrate. These depressed P/O values seem to reflect a differential temperature sensitivity of the enzymes involved in succinate respiration and oxidative phosphorylation. The observation that the rat mito-chondrial P/O ratios were normal at the lower incubation temperatures when [beta]-hydroxybutyrate was substituted for succinate suggests that the differential temperature sensitivity may be substrate specific. The similarities of the temperature-response patterns of the mitochondria from the aroused bats, torpid bats, and cold-acclimated rats indicate that the ability of the animal to hibernate is not reflected in a differential effect of cold exposure on the coupling of liver mitochondrial oxidative phosphorylation and succinate respiration.