CONCENTRATION AND TURNOVER OF CYTOCHROMEcIN SKELETAL MUSCLES OF WARM- AND COLD-ACCLIMATED RATS

Abstract

Cytochrome c concentration in ventrolateral abdominal muscles of cold-acclimated rats was significantly higher than in corresponding muscles of warm-acclimated rats, but concentration of this protein in gastrocnemius muscle was similar in both groups of animals. Average concentration of cytochrome c in all skeletal muscles was higher in cold- than in warm-acclimated rats. Total amount of skeletal muscle cytochrome c per rat, calculated as the product of estimated total muscle mass and average concentration of cytochrome c, was similar in both groups. The fractional rates of turnover of skeletal muscle cytochrome c, labelled by administration of 1-14C-acetate to warm- and cold-acclimated rats, were, respectively −0.050 ± 0.003 and −0.047 ± 0.005 per day, corresponding to half-lives of 13.8 and 14.8 days. The rate of turnover of cytochrome c was 0.5 mg cytochrome c per rat per day at both acclimation temperatures. A value of 14 days for the half-life of sarcosomes is suggested.