Rainbow trout and human cells in culture for the evaluation of the toxicity of aquatic pollutants: A study with lead

Abstract

Rainbow trout (RTG-2) and human skin epithelial cells (NCTC 2544) were used as bioassay organisms for the evaluation of the toxicity of lead, an aquatic pollutant. The cell lines were grown as monolayers at 15°C (RTG-2) and 37°C (NCTC 2544) in minimal essential medium supplemented with 10% fetal bovine serum. RTG-2 cells were exposed to 100 ppb and 2.4 ppm lead; NCTC 2544 cells were exposed to 2.4 and 10 ppm lead. These concentrations were selected on the basis of LC 50 values determined in vitro with the rainbown trout. Exposure to lead was maintained for the period of time required for an inoculum of 10 5 cells (RTG-2) or 5 × 10 4 cells (NCTC 2544) to reach confluency in the controls in a 60 mm Petri dish: 18–20 days for RTG-2 and 6–7 days for NCTC 2544. Every 2 days (RTG-2) or every day (NCTC 2544) the medium was renewed and 3 Petri dishes were used in each group for the determination of the following parameters: total protein, total DNA, total RNA content and the incorporation of [ 3H]thymidine in DNA and [ 14C]uridine in RNA. At 2.4 ppm, lead induced a dramatic inhibition in the increase of total protein, DNA and RNA content of RTG-2 cells. These effects were seen as early as 6 days after lead was added to the cultures. The incorporation of labelled precursors was equally much lower in the treated samples (2.4 ppm) compared to the controls. NCTC 2544 cells appeared to be less sensitive to lead than RTG-2 cells. After 6 days of exposure of NCTC 2544 cells to either metal concentration, no significant effect was observed on any of the five parameters measured. Compared to in vivo classical bioassays, rainbow trout cells in culture showed an excellent sensitivity for the detection of lead toxic effects.