Table II.

Functional features of SIRK channel

Selectivity
PRb/PK			PNa/PK
0.31 ± 0.01 (3)			<2.10−3 (3)
pH effect on gating (n = 4)
pHe/pHi	7.5/7.4	6.0/7.4	7.0/7.4	7.0/7.0
Za	2.79  ± 0.08	2.8  ± 0.07	2.8  ± 0.01	2.79  ± 0.02
Ea50	−158  ± 2	−129  ± 2	−151  ± 2	−142  ± 2
Caesium block (0.1 mm, inhibition in % of control, n = 3)
−160 mV	−140 mV	−120 mV
83 ± 2	92  ± 5	96  ± 2

Permeability ratios were determined from the reversal potential obtained in external solution containing 100 mm XCI (X⁺ being K⁺, Rb⁺, or Na⁺), 1 mm CaCl₂, 1.5 mm MgCl₂, and 5 mm HEPES-NaOH (pH 7.4), as previously described (Véry et al., 1995). Gating parameters were determined in solutions described in Fig. 3. The gating parameters z_a and E_a50 were obtained as previously described (Lacombe and Thibaud, 1998). Each value is mean ± se (no. of oocytes). Cs⁺ block was determined in 10 mm K⁺ solution.