MEND responses induced by the application and removal of SDS. Cytosolic solutions contained 2 mM ATP and 0.2 mM GTP. (A) Within a few seconds, 50 µM SDS caused a small increase of C_m, and then C_m continued to rise nearly linearly. MEND occurred within seconds upon SDS removal. (B) Rapid pipette perfusion of 150 µM SDS into a BHK cell with 2 mM ATP was without effect on C_m. Thereafter, membrane fusion occurred normally upon the activation of Ca influx by NCX1. Finally, the application and removal of 50 µM of extracellular SDS caused a 50% MEND response over 20 s after SDS was removed.