Oxidative phosphorylation in liver mitochondria from cold-exposed rats

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Abstract
The efficiency of oxidative phosphorylation in mitochondrial preparations from rats exposed to 25°C and to 0°–2°C for 1 day, 2 weeks, 1 month and 3–6 months was compared by direct in vitro estimation of the P/O ratio and by measurement of respiratory control. In addition, other criteria, such as aging and Ca++ sensitivity, were used to investigate the lability of the phosphorylative systems under conditions which tend to alter the mitochondria structure. The results confirm earlier reports that in mitochondria from rats chronically exposed to cold oxidative phosphorylation is depressed, and show further that the latter are more susceptible than that of the controls to factors which uncouple this process. Measurements of optical densities also indicate that the structure of mitochondria from cold-acclimated rats is the more susceptible to aging. Such changes did not appear in rats exposed to the cold for only 1 day.