Figure 2

L-type Ca²⁺ conductance in γ ₁ knockout myotubes. A) Whole-cell L-type Ca²⁺ current when control (+/+), γ₁ het (+/-), or γ₁ null (-/-) myotubes are depolarized to either -10 mV, +30 mV or +60 mV from a holding potential of -40 mV. The pulse duration was 500 ms. The cell capacitance was 262 pF, 221 pF, and 286 pF, for the control, γ₁ het and γ₁ null cells, respectively. B) Voltage dependence of the Ca²⁺ conductance for 8 control, 8 γ₁ het and 12 γ₁ null cells. The curves correspond to a Boltzmann fit of the population mean with the following parameters. G_max = 132 pS/pF, V_1/2 = 13.4 mV and k = 5.3 mV for control cells; G_max = 160 pS/pF, V_1/2 = 13 mV and k = 5.8 mV for γ₁ het cells; and G_max = 167 pS/pF, V_1/2 = 9.9 mV and k = 4.6 mV for γ₁ null cells.