Figure 9.

Rate constants for entry (A) and exit (B) of Ca²⁺, from microscopic and macroscopic data. “Single-channel” rates are reciprocals of closed times (B), or the reciprocal of the open time minus the reciprocal of the open time in 0.1 μM Ca²⁺_o (A), n = 3–4. “Frequency domain” time constants are from the fast corner frequency as in Fig. 7, and the steady-state block (p_B) was estimated from the steady-state currents in 10 μM Ca²⁺_o, divided by the steady-state current in 0.1 μM Ca²⁺_o (assumed to be zero block), n = 3. “Time domain” rates were calculated from time constants (Fig. 6 D) and steady-state block (from Fig. 6 E); n = 9 for 10 μM Ca²⁺_o and n = 3 for 3 μM Ca²⁺_o. For macroscopic data (frequency domain and time domain), rate constants were calculated assuming 1/τ = k_on + k_off, and p_B = k_on/(k_on + k_off); thus k_on = p_B/τ, k_off = 1/τ − k_on. In A, bimolecular rate constants were calculated by dividing k_on by the free Ca²⁺_o. The same symbols were used in A and B.