Camptothecin inhibits macromolecular synthesis in mammalian cells but not in isolated mitochondria of E

Camptothecin at 1 mg per ml inhibited DNA synthesis in HeLa cells 60% and in L5178Y cells 47% but had no effect on rat liver or brain mitochondria or E. coli DNA synthesis. RNA synthesis in HeLa cells was inhibited 67% in HeLa cells and 73% in L5178Y cells by 1 mg camptothecin per ml, but no inhibition of mitochondrial or E. coli RNA synthesis occurred. Protein synthesis was slightly inhibited by camptothecin in the mammalian cells, but mitochondrial and E. coli protein synthesis was unaffected. Camptothecin at levels as high as 1 mg per ml had no effect on glycoprotein synthesis in mitochondria or the mammalian cells or on lipopolysaccharide synthesis in E. coli.