Figure 6.

Zn²⁺ potentiated RyR2 activity in Mg23 knock-out mice. A, representative Ca²⁺ current fluctuations from bilayer experiments using cardiac SR vesicles isolated from wild-type and Mg23-knock-out mice. Functional MG23 channel gating was observed in wild-type experiments but not in Mg23 knock-out experiments. Open (O) and closed (C) states are indicated. Holding potential was 0 mV, and Ca²⁺ was used as the permeant ion. Cytosolic free Ca²⁺ was 5 μm. B, scatter plot showing noise analysis data from wild-type experiments where only MG23-mediated Ca²⁺ currents were observed. Mean average current is shown after incremental addition of Zn²⁺ to the cis chamber. C, representative Ca²⁺ current fluctuations from bilayer experiments using cardiac SR vesicles isolated from Mg23 knock-out mice showing functional RyR2 channel gating in the absence and presence of 1 nm Zn²⁺ added to the cis chamber. The lower panel scatter plot shows RyR2 channel open probability under these conditions. D, paired all-points-amplitude histograms under conditions described in C. Data shown are the mean ± S.D., n = 3, with * and ** indicating significant differences (p < 0.05 and p < 0.01), respectively, from control. NS, not significant.