Table 1. Effects of pH_i, pH_o, and [Ca²⁺]_o on channel N′P_o/V_m relationships.

Condition	K	V1/2	N′Po min	N′Po max	R2
	mV	mV	%	%
pHi 7.0 (5)	20.8 ± 3.9	41.7 ± 8.4	19.4 ± 6a	111.0 ± 8.2	0.961 ± 0.027
pHi 7.4 (7)	19.0 ± 6.1	28.8 ± 8.4	19.6 ± 4.5a	106.7 ± 8.2	0.905 ± 0.022
pHi 7.6 (5)	22.9 ± 10.1	29.6 ± 5.9	38.4 ± 11.3	106.4 ± 4.4	0.953 ± 0.016
pHi 7.8 (5)	20.4 ± 4.6	32.8 ± 4.9	47.3 ± 3.3a	104.8 ± 1.7	0.945 ± 0.069
pHo 6.6 (5)	19.5 ± 6.2	58.0 ± 5.1b	33.1 ± 3.3	124.1 ± 12	0.934 ± 0.016
pHo 7.4 (5)	13.1 ± 2.4	33.0 ± 8.5	35.0 ± 3	105.0 ± 3.2	0.890 ± 0.03
pHo 8.0 (4)	23.3 ± 6.5	20.8 ± 4.6	37.0 ± 4.5	109.8 ± 3	0.927 ± 0.04
[Ca2+]o 0 mM (5)	21.2 ± 5.1	34.3 ± 12.6	10.4 ± 2.5	119.5 ± 11.2	0.979 ± 0.015
[Ca2+]o 5 mM (4)	29.1 ± 5.1	31.4 ± 11.3	6.9 ± 5.3	118.7 ± 11.8	0.965 ± 0.012

Mean parameters from Boltzmann fits (see Materials and methods) of individual N′P_o/V_m relationships in the cell-excised inside-out configuration in the conditions given in the left column. In each condition, N′P_o values were normalized to their respective values at V_m 80 mV. Data are given as means ± SEM for the number of fits indicated in parentheses. For each condition, a measure of the goodness of fit (R²) is also given. One-way ANOVA revealed significant differences between the N′P_omin means of pH_i groups (P < 0.005) and between the V_1/2 means of pH_o groups (P < 0.01). Parameters under 0 and 5 mM [Ca²⁺]_o were not statistically different (unpaired Student’s t test).

^aP < 0.01 versus pH_i 7.8 (Holm-Šidák multiple comparison procedure).

^bP = 0.02 versus pH_o 8.0 (Holm-Šidák multiple comparison procedure).