We examined the effect of sodium fluoride on uptake of tritium-labeled T-2 toxin (molecules of toxin/cell) in Chinese hamster ovary (CHO) and African green monkey kidney (VERO) cells. Correlations were made to temperature (22 and 37 degrees C) and toxin concentration (0.001 and 0.01 microgram/ml) over time (0-180 min). As expected, toxin uptake increased in both cell types with increasing time and temperature. VERO cells exhibited significant (P less than 0.05) increases in the rate (i.e. slope) of toxin uptake under all parameters, while the rate of toxin uptake in both cell types was generally greater at 37 degrees C compared to 22 degrees C. The rate of equilibrium was affected by both temperature and sodium fluoride. At 37 degrees C toxin uptake plateaued by 30 min in the presence of sodium fluoride. At 22 degrees C the rate of toxin uptake was slower, with or without sodium fluoride present. Statistical analysis of individual time points along the curve demonstrated that sodium fluoride significantly increased cell-associated toxin at most time points. Analysis of the slopes of uptake curves from 0 to 20 min indicated significant (P less than 0.05) differences in the rates of T-2 uptake in both cell types and toxin doses in the presence of sodium fluoride. The increase in toxin uptake in the presence of sodium fluoride was not due to altered cell membrane permeability caused by sodium fluoride. This study demonstrates that sodium fluoride significantly increases cell-associated T-2 toxin and the rate of toxin uptake in two cultured cell lines.