Fatty tetracycline-induced steatosis is shown to reduce levels of mitochondrial and microsomal cytochromes. A decrease of microsomal cytochromes in the liver of hypoxia-resistant animals was similar to that of hypoxia-sensitive ones. This decrease was different for hypoxia-resistant and hypoxia-sensitive animals: for the former only cytochrome a declined, in the latter case cytochromes c+, c1 and a.