Changes in glutathione-redox balance induced by hexachlorocyclohexane and lindane in CHO-K1 cells

Abstract

1. The basal cytotoxic effect of the organochlorine pesticides hexachlorocyclohexane and lindane on CHO-K1 cultures was assessed at fractions of their lethal doses as determined by the neutral red incorporation (NRI) assay (NRI_6.25, NRI_12.5 and NRI₂₅). The sulphur-redox cycle enzymes glutathione peroxidase, glutathione reductase and glutathione S-transferase, and total and oxidized glutathione were evaluated at several points during the standard growth curve of the cultures. 2. After incubation with each compound for 24h, both glutathione peroxidase and reductase showed a substantial increase at the lowest exposure doses (NRI_6.25) - more significantly for lindane than for 1,2,3,4,5,6-hexachlorocyclohexane (HCH) - and dropped at higher doses of both compounds. The reduced and oxidized glutathione content was greatly diminished at the lower exposures, whereas the total glutathione content was higher at NRI_12.5 values. 3. Changes in cell membrane integrity were assessed for a wide range of pesticide concentrations with the lactate dehydrogenase release assay and lipid peroxidation. Membrane leakage and peroxide production were significantly enhanced at concentrations of HCH 50µg ml⁻¹, although this effect was not significant at lindane concentrations <200µg ml⁻¹. 4. Lipid peroxidation increased with exposure to HCH at concentrations as low as NRI_6.25, whereas in the case of lindane, this increase was only significant at doses of NRI₂₅ and above.