Toxicological evaluation of surface-water samples in sensitised cultured fish cells compared with the Microtox (R) method

A previously described neutral red uptake-inhibition assay on cultured fath ead minnow (FHM) fish cells revealed a good correlation with fish toxicity data. The assay was made more sensitive by reducing the number of cells, by using a longer treatment period, and by simultaneous treatment of the cell s with sodium dodecyl sulphate and L-buthionine (S,R)-sulphoximine. The flu orimetricaliy quantified protein content was then used as the endpoint. The results were compared with toxicity data obtained by the Microtox(R) metho d with the bacterium, Vibrio fischeri. A series of 82 surface-water samples were investigated. Cell quantity-dependent and sample concentration-depend ent reductions in total protein content were observed. In all, 32 samples w ere toxic in the FHM assay. Of the seven samples that were shown to be toxi c in the Microtox assay, only three were also toxic in FHM cells. No linear relationship was found for the toxicity results obtained with the two meth ods. Further research to explain the significance of the many positive resp onses and to identify possible confounding factors will increase the reliab ility of the sensitised FHM cell assay.