Mitochondrial cytochrome concentrations in rat heart and liver as a consequence of different hypoxic periods

Rat heart and liver cytochrome concentrations were determined after three hypoxic conditions (atmospheric pressure 50.5 kPa, 40.8 kPa and 38.0 kPa) lasting one week and two weeks. The heart showed clear hypertrophy which was 38% in most severe hypoxia (38 kPa, 2 weeks). A small decline in the liver weight to body weight ratio was observed, this decrease being 21% in the most severe case. During the hypoxic periods the mitochondrial cytochrome concentration decreased. This phenomenon was more obvious when the degree of hypoxia was increased and more pronounced after 2 weeks than one week. The heart and liver showed quite similar patterns in this respect. In most severe hypoxia the decreases in the liver were 29% for cytochrome aa3, 30% for cytochrome b, 20% for cytochrome c and 15% for cytochrome c1, with the concentrations expressed on mitochondrial protein basis. The corresponding values in the heart were 31%, 43%, 28%, and 22%. It can be concluded that in mammals the mitochondrial cytochrome content probably varies according to the amount of oxygen available.