Etx induces ATP release in 1G11 mouse endothelial cells. ATP release was detected by GFP-Etx action in 1G11 cells (A) and in MDCK cells (B) but not in NIH/3T3 cells (C). The % of ATP released with respect to the total ATP content was compared between GFP-Etx treated cells (gray columns, D) and GFP-pEtx treated cells (white columns, D). In A, B and C, cells were incubated with GFP-Etx (red line) or GFP-pEtx (black line) for 120 min. The cells were treated with Triton X-100 for the last 15 min to quantify total ATP content (inserts, A, B and C). GFP-Etx induced the release of 90% of the ATP content in MDCK cells; 60% in 1G11 cells and no ATP release was detected in NIH/3T3 cells, used as a negative control (D). Each condition was run in quadruplicate and in four independent experiments (****P < 0.00001), (n.s non-significant). Arrowhead marks the beginning of incubation with the GFP-Etx or GFP-pEtx.