Oxidations in kidney mitochondria of heat-exposed rats: regulation by cytochrome c.

Exposure of rats to higher environmental temperature (36-37 degrees C) decreased the capacity of their kidney mitochondria to oxidize succinate. The decrease was corrected on the addition of exogenous cytochrome c. Kidney mitochondria of heat-exposed animals showed decreased rates of H2O2 generation when alpha-glycerophosphate, but not succinate, was used as electron donor. These mitochondria also showed decreased activity of alpha-glycerophosphate dehydrogenase but not of succinate dehydrogenase. The content of cytochrome c in kidney mitochondria of heat-exposed animals was low even though the concentration of the pigment in the whole tissue did not decrease. Starvation as well as administration of an antithyroid agent like propylthiouracil simulated some of the effects of heat exposure on kidney mitochondria, but the cytochrome c-dependent reversal of inhibition of oxidation was obtained only in heat exposure.