Woodier et al. (1) report that the cardiac type 2 ryanodine receptor channel (RyR2) shows two modes (sites) of regulation by zinc. When calcium is activating the channel, zinc increases channel Po around 100 pm (high affinity), whereas in the absence of calcium, zinc must reach 100 nm (low affinity) before channel Po is increased (compare Fig. 1 with Fig. 4, model in Fig. 10). We would like to offer an alternate interpretation of these data. In order to achieve nominally 0 free calcium, 1 mm BAPTA (2,2′-(ethylenedioxy)dianiline-N,N,N′,N′-tetraacetic acid) was added.