Reactivation of membrane charge movement and delayed potassium conductance in skeletal muscle fibres.

1. Intramembrane charge movement has been measured in striated muscle subjected to prolonged depolarization but repolarized to -100 mV for up to 100 sec. The method of measurement allows identification of charge or charges which are 'reprimed' by repolarization. 2. Charge 'reprimed' by repolarization appears to differ in its voltage distribution from charge detected in a permanently polarized fibre. The difference is probably due to the different pulse sequences used in the two measurements and to the fact that there appear to be several species of intramembrane charges with different transition potentials and different steepness of voltage distribution (V and k in eqn. (14): see below). 3. Potassium conductance is reprimed by repolarization following inactivation by depolarization. When the repriming potential is -100 mV the process appears to be in two stages; repriming to a value rather less than half the final value takes place exponentially with a time constant of approximately 40 sec; subsequently repriming to the final value is very slow. At a repriming potential of -140 mV repriming to the final value )1--2 mmho/microF) takes place exponentially with a time constant of approximately 17 sec.