High-conductance chloride channels in BC3H1 myoblasts.

The existence of a high-conductance voltage sensitive chloride channel in BC3H1 myoblasts is documented. The conductance of the channel in symmetrical 150 mmol/l sodium chloride is around 400 pS. The probability of the channel being in the open state decreases with increasing of the imposed voltage from holding potential (0 mV) in both the depolarizing and the hyperpolarizing direction respectively. The bell-shaped open probability plot is asymmetrical, and can be fitted by two Boltzmann equations with different Vh and kn constants; the fitted values were -53 mV and -8.4 respectively for the negative side and +41 mV and +10.2 for the right side. When the unit Cl currents to rectangular pulses are summated the resulting total ionic Cl current shows relaxation, which increases with the amplitude of the pulse. The activation as well as the shape of the current can be significantly influenced by varying the amplitude and the direction of prepulses or holding potential. The high-conductance Cl channel shows several substrates (at least four with amplitudes of around 100 pS); frequently accompanied by flickerings.