[Biochemical heterogeneity of mitochondria].
Rat liver mitochondria were fractionated on the basis of their sedimentation coefficients in the gradient of ficoll. The fractions ("heavy", "middle" and "light" mitochondria) were heterogeneous with regard to the content of protein, DNA, cytochrome a + a3 and respiratory activity. Heterogeneity of mitochondria did not result from the damage or microsomal and lysosomal contamination. The biosynthesis of DNA, RNA and proteins in the different fractions of mitochondria was studied. In vivo incorporation of radioactive precursor into RNA was highest in the fractions of "middle" mitochondria, whereas in vitro the "heavy" mitochondria showed maximum activity in the synthesis of RNA. In vitro DNA synthes was maximum in the fractions of "heavy" mitochondria, protein synthesis in "heavy" and "light" mitochondria. Activity of the synthesis of RNA, DNA and proteins in vitro depends on the content of DNA and cytochrome a + a3 in the different fractions of mitochondria. It is supposed that heterogeneity of mitochondria may be connected with their biogenesis.