Morphological transformation of Syrian hamster embryo cells in primary culture by malachite green correlates well with the evidence for formation of reactive free radicals.

Malachite green (MG) (green crystals with metallic luster and very soluble in water) is highly cytotoxic to mammalian cells and also acts as a liver tumor promoter. In view of its industrial importance and possible exposure to individuals, MG poses a potential environmental health hazard. We have studied the effect of MG on the formation of morphologically transformed colonies using Syrian hamster embryo (SHE) cell transformation assay. MG induced a dose-related increase in the formation of transformed foci, the optimum concentration being 0.05 micrograms/ml. Electron spin resonance (ESR) analysis using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin-trapping agent showed the formation of reactive free radicals during the in vitro metabolism of MG. The present study suggests a close relationship between the morphological transformation of SHE cells by MG and the possible involvement of reactive free radical formation.