CYTOTOXIC EFFECTS OF SUBLETHAL CONCENTRATIONS OF MALACHITE GREEN IN ISOLATED HEPATOCYTES FROM RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

The fish therapeutic dye malachite green 4-[bis]4-(dimethylamino)pheny l[phenyl]-methylene]) was tested for sublethal cytotoxic effects at co ncentrations of 0, 0.01, 0.1 and 1 mg/litre. Isolated hepatocytes of r ainbow trout (Oncorhynchus mykiss) were used to evaluate its cytotoxic ity in a subcellular system and compare in vitro effects with those of in vivo experiments. Whereas conventional viability tests [trypan blu e exclusion, lactate dehydrogenase (LDH) release] failed to detect any acute toxic effect by malachite preen exposure, electron microscopy r evealed time- and dose-dependent responses of isolated hepatocytes wit h first reactions after 1-day exposure to 0.01 mg/litre. Whereas hepat ocellular nuclei took a more irregular shape, cytoplasmic changes comp rised an increase in heterogeneity of mitochondrial shape, closer asso ciation of mitochondria with cisternae of the rough endoplasmic reticu lum (RER), fractionation, dilation and vesiculation of RER, formation of cytoplasmic membrane whorls, glycogen bodies and induction of myeli nated bodies and cytoplasmic vacuoles. In agreement with conclusions d rawn from in vivo experiments, in vitro data provided evidence for nuc lei and mitochondria as the major cellular targets of malachite green in both fish and mammals.