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Concentration of cytochroms in the liver of adult male rats has been studied during the acclimation to cold. One group of rats was kept at about 24 degrees, another at 2--4 degrees. After a month of acclimation to cold the cytochroms concentration in the liver increased, whereas the mitochondrial concentration of cytochroms remained unchanged. It is possible to distinguish three steps of cytochroms concentration changes; 1. on the 9th day of acclimation to cold cytochroms concentration increased 1.5--2 times; 2. by the 14th day the cytochroms concentration decreased (to the control level and lower); 3. after about one month of acclimation to cold the cytochroms concentration increased again. In the skeletal muscle it increased on the 14th (but not on the 9th) day.

Injections of albino rats with antioxidants of the ionol group cause cyclic changes in the energy state of liver mitochondria which are correlated with changes in the fatty acid composition of mitochondrial membranes. The increase in the degree of coupling between oxidation and phosphorylation coincides in time with the increment in the content of saturated fatty acids and a decrease in the unsaturated fatty acid content in the total fraction of mitochondrial membrane lipids. Conversely, the activation of the external pathway of NADH oxidation and a decrease of the respiratory control are correlated with the diminution of the saturated fatty acid content and an increased percentage of unsaturated fatty acids. These changes are especially well pronounced in the case of fatty acids carrying 18 carbon atoms.

An injection of ionol-type antioxidants stimulates fast oxidation of extramitochondrial NADH in isolated liver mitochondria via an external pathway, which is sensitive to cyanide and resistant to amital and antimycin A. This activation is accompanied by a decrease in cytochrome a and cytochrome (c + C1) levels in liver homogenate. Part of the cytochrome c pool can be removed by washing the antioxidant-treated mitochondria. It is assumed that the injection of the antioxidants leads to desorption of the cytochrome c bound to the inner membrane into the intermembrane space of mitochondria. This cytochrome acts as a linking agent between NADH cytochrome c reductase of the outer mitochondrial membrane and cytochrome c oxidase of the inner membrane. The Li-derivative of ionol (5 x 10(-4) and 10(-3) M) decreases the transmembrane potential of the submitochondrial particles from bovine heart by 15-20%.