Pyridine Nucleotide-Cytochrome C Reductases in Acclimatization to Cold

A study of the pyridine nucleotide-cytochrome c reductases activity was carried out in liver cell fractions (mitochondria and microsomes) from cold exposed hamsters. Control animals were studied simultaneously. Both DPNH- and TPNH-cytochrome c reductases had a higher activity in microsomes of cold adapted hamsters than in those of controls; the latter nevertheless increases more conspicuously. In the mitochondria, in turn, these 2 systems did not show significant changes. The possible implication of these findings in cold adaptation is discussed.