Fig. 4. Voltage-dependent Ca2+release. ( A ) Myotubes were patch clamped at a holding potential of −80 mV and depolarized to increasing potentials for 2 s. Changes in intracellular Ca2+concentrations were monitored fluorometrically. Activation of the voltage dependent Ca2+channels results in an intracellular release of Ca2+. (MHN = cell from a normal individual; MHS = cell from an individual diagnosed as susceptible to malignant hyperthermia). ( B ) The voltage-dependent Ca2+release is shifted to more negative potentials in MHS cells. ( C ) This shift is not due to a change in the properties of voltage-activated L-type Ca2+channel. The current–voltage relation shows the same activation kinetics in MHS and MHN cells.