Effect of methyl-β-cyclodextrin (MβCD) on cytotoxicity of TDH. MβCD inhibited TDH cytotoxicity for HeLa, Rat-1, and CHO-K1 cells. Each cell line was exposed to TDH at 20 μg/ml for 3 h for HeLa cells, at 10 μg/ml for 30 min for Rat-1 cells, and at 100 μg/ml for 3 h for CHO-K1 cells. Cytotoxicity was evaluated by determining the quantity of lactate dehydrogenase released. PBS was used as a negative control (0%), and the lysis buffer included in Cytotox 96 nonradioactive cytotoxicity assay kits (Promega) was used as a positive control (100%). Data are presented as the means for triplicate experiments. Error bars represent standard deviations (SD). Asterisks indicate significant differences from the results obtained with nontreated cells (P < 0.05).