Fig. 9.

Calcium currents are indistinguishable in wdl/wdl and wdl/+ mice. Leak subtracted currents recorded in RBCs from wdl/+ (A1, n = 11; B1, n = 8; D1, n = 7) and wdl/wdl mice (A2, n = 10; B2, n = 10; D2, n = 8) during 100-ms depolarizing voltage pulses. The pipette solution contained CsMeSO₄ to block potassium currents. SR 95531 (10 μm), TPMPA (30 μm) and strychnine (1 μm) were added to the bath solution to block inhibitory currents. Depolarizing steps were applied in 10-mV increments from a holding potential of −70 mV (A) to activate mainly L-type calcium channels, or −100 mV (B) to activate both L- and T-type currents. (C) The amplitudes (± SEM) for average current–voltage relations from RBCs in the +/wdl (filled symbols) and wdl/wdl mouse (open symbols) were measured at a fixed time-point 10 ms after the onset of the voltage pulse. Triangles show currents measured from a holding potential of −70 mV, and circles show currents measured from a holding potential of −100 mV. (D) Steady-state inactivation of the transient component of the calcium current was generated by a 1-s pre-pulse to potentials between −110 and −40 mV. (E) The symbols show the difference between the current measured 8 ms after the onset of the test pulse to −40 mV, and 90 ms later, at the end of the test pulse. Data from the +/wdl and mutant animals have been scaled for comparison. The smooth lines show a fit to a Boltzmann function, with half-inactivation potentials of −79 and −80 mV for the +/wdl and mutant data, respectively. The slope factors were 4.9 and 6.3 mV.