Fig. 2.

Cytotoxic effects of Stx1 and Stx2 on HK-2 cells. HK-2 cells (5 × 10⁴ cells per well) were incubated with different concentrations of either Stx1 or Stx2, as indicated. After incubation for 24 h (A), 48 h (B), or 72 h (C), viable-cell numbers were estimated by MTT assay. The graphs depict percent cell viability compared to untreated cells and represent the means ± SEM of three independent experiments. The asterisks denote significant differences between cells stimulated with Stx1 and Stx2 (*, P < 0.05; **, P < 0.01).