FIGURE 7.

Extracellular Ca²⁺-mediated membrane repair mechanism to hinder CTX A3-induced cytotoxicity. A, extracellular Ca²⁺ influx into Fluo-3-loaded NIH3T3 cells was induced by CTX A3-specific (but not by CTX A2 and A4) pore formations within 1 min. B, depletion of extracellular Ca²⁺ enhanced CTX A3 internalization. C, plasma membrane repair of CTX A3-permeabilized NIH3T3 cells was Ca²⁺-dependent. The blue color for Hoechst staining indicates the nuclear location; propidium iodide influx, stained red, indicates that the cells failed to reseal. D, endocytosis of fluorescence-labeled dextran (4 kDa) was significantly enhanced by CTX A3 under Ca²⁺-free condition. Bar = 20 μm. Data were mean ± S.E. (n = 5); **, p < 0.01.