Protection of RAW 264.7 cells (A) and Fischer F344 rats (B) from LeTx-induced death by AmPrβCD. (A) RAW 264.7 cells were incubated with various concentrations of AmPrβCD and LeTx or medium was added. PA was used at three final concentrations (1000, 500, and 200 ng/ml). LF was constant at a final concentration of 100 ng/ml in all experiments. After 3 h, viability was determined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Percentage viability was calculated relative to cells treated with medium alone. (B) Three groups of rats (n = 3 per group) were injected intravenously with 10 μg of LeTx (10 μg of PA plus 10 μg of LF) alone, or mixed with AmPrβCD (0.25 mg or 1.25 mg). A fourth group of rats (n = 3) was pretreated with 1.25 mg of AmPrβCD and injected intravenously with LeTx after 30 min. Survival was monitored for each group continuously over 8 h and periodically for survivors over a period of 7 days.