[An assessment of relative contribution of DNA reparation and glutathione-dependent pathway of detoxification in response of Chlorella algae to uranium].

Toxicity of 238U (as uranyl nitrate) in the range of 0.04-84 micromol/L for Chlorella (Chlorella vulgaris Beijerink) was investigated. The best approximation for relationship between the toxic effect in Chlorella and 238U Concentrations is observed using the hormetic Brain-Cousens model. A significant increase in Chlorella biomass, estimated as the optical density of suspension, as well as the level of fluorescence of chlorophyll was observed in the range of 17-29 micromol/L with the maximum at a 23 micromol/L. It was found that 38 micromol/L of 238U induced a significant toxic effect; while at 53 micromol/L inhibition of Chlorella biomass by 50% was observed. According to our observations, the toxic effect of low concentrations of 238U was increased in the presence of 0.02 micromol/L caffeine (used as inhibitor of DNA repair processes) or DL-buthionine-(S, R)-sulfoximine (used as a selective inhibitor of the key glutathione biosynthetic pathway).