Unequal inhibition of protein synthesis in mitochondria of Zajdela hepatoma and rat liver after in vivo treatment with cis-diamminedichloroplatinum (II).

The effect of in vivo administered cis Pt(II) on mitochondrial and overall cellular protein synthesis in hepatocytes from regenerating rat liver and Zajdela hepatoma was examined. In both types of cells the overall cellular protein synthesis was inhibited by the drug approximately to the same extent (about 50%). Protein synthesis in mitochondria of Zajdela hepatoma was practically unaffected by the drug, whereas that in rat liver was inhibited similarly as was the overall cellular protein synthesis. Cis Pt(II) treatment had no detectable effect on the electrophoretic pattern of peptides synthesized in mitochondria of rat liver and Zajdela hepatoma. Relative content of cytochrome oxidase subunit IV to subunit II in Zajdela hepatoma mitochondria decreased upon cis Pt(II) treatment. The amount of platinum bound to Zajdela hepatoma mitochondria upon in vivo cis Pt(II) treatment was about two times lower than that bound to mitochondria of rat liver. It is concluded that protein synthesis in Zajdela hepatoma mitochondria is more resistant to in vivo cis Pt(II) treatment than the process in mitochondria of rat liver, and that this effect results from lower binding of cis Pt(II) and/or its derivatives to the tumor mitochondria.