Levels of cellular glutathione and metallothionein affect the toxicity of oxidative stressors in an established carp cell line

The comparative toxicity of a variety of oxidative stressors was studied in the epithelioma papulosum cyprini line from carp using the neutral red cytoxicity assay. LC50ʹs decreased in the order t-butylhydroperoxide>hydrogen peroxide>diquat>paraquat. The cytoxicity of hydrogen peroxide was significantly reduced when the cells were grown in L-15 medium rather than MEM and this could be attributed to elevated cellular glutathione and metallothionein levels and higher activities of GSH-dependent detoxification systems. The protective effect of metallothionein in radical scavenging was demonstrated by decreased toxicity of the redox-cycling toxicants, diquat and menadione after metallothionein levels had been pre-induced by Cd-exposure. This study demonstrates the relationship between toxic effects of oxidative stressors and expression of detoxification systems in fish.