Use of fish gill cells in culture to evaluate the cytotoxicity and photocytotoxicity of intact and photomodified creosote

The influence of ultraviolet (UV) irradiation on creosote toxicity was inve stigated with the rainbow trout (Oncorhynchus mykiss) gill cell line, RTgil l-W1, and two indicator dyes, alamar Blue(TM) and 5-carboxyfluorescein diac etate acetoxymethyl ester. These monitor redox potential and membrane integ rity, respectively. After solubilization and chemical analysis, creosote wa s presented to cells in the dark to measure cytotoxicity or concurrently wi th UV irradiation to evaluate photocytotoxicity. Additionally, creosote was photomodified by 2 h of UV irradiation before presentation to cells in the dark or together with UV. Cytotoxicity was detected only at high nominal c reosote concentrations, but photocytoxicity occurred at creosote concentrat ions 35-fold lower. All the aromatic hydrocarbons in creosote appeared to c ontribute to cytotoxicity, but photocytotoxicity was due only to the fluora nthene, pyrene, anthracene, and benzo[a]anthracene in the mixture. Photomod ified creosote was much more cytotoxic than intact creosote and this differ ence was most pronounced in the alamar Blue assay. Likely, this was due to photomodification products that impaired the mitochondrial electron transpo rt chain. Photomodified creosote was slightly less photocytotoxic than inta ct creosote. Overall these results indicate that UV irradiation potentially enhances the toxicity of creosote to fish in several different but signifi cant ways.