Figure 3.

Effect of a rapid reduction in the cotransported current. After a stabilization period at a membrane potential of −100 mV, 5 mM αMG is introduced in the bathing solution. After establishment of a steady-state cotransport current (a 60-s period), the membrane potential was stepped to 0 mV to abruptly reduce the cotransport current. At t = 300 s, αMG was removed to allow a determination of background current at 0 mV. The volume data were either fitted according to the water-cotransport hypothesis (240 water molecules/αMG molecule, dashed line) or by using the osmolyte accumulation model (full line).