Table 1.

Intracellular Na⁺ activities and electromotive force for Na⁺ across the cell membrane in X. laevis oocytes expressing the rENaC and various α and/or β P-ATPase subunits

Injected cRNAs	[Na]i, mM	Na+ electromotive force, mV	n
rENaC	38.6 ± 1.9	−50.6 ± 2.0	10
rENaC + βg	34.7 ± 3.7NS	−48.7 ± 4.7NS	5
rENaC + β1	33.9 ± 1.7NS	−45.1 ± 1.9NS	9
rENaC + αgβg	35.5 ± 1.9NS	−49.4 ± 1.6NS	7
rENaC + α1β1	9.4 ± 0.7***	−57.6 ± 0.7***	14
rENaC + αcβg	17.8 ± 1.3***	−57.0 ± 1.1***	11

Oocytes were coinjected with rENaC α, β, and γ subunits cRNAs alone or with β_g, β₁, α_gβ_g, α₁β₁, and α_cβ_g subunit cRNAs. After a 2-day incubation in amphibian Ringer’s solution, [Na]_i and V_m were measured by using intracellular Na⁺-selective microelectrodes. The electrochemical potential for Na⁺ across the oocyte membrane was calculated as V_m − E_Na, where V_m is the measured membrane potential difference, and E_Na is the equilibrium potential for Na⁺, calculated from extracellular Na⁺ concentration (using an activity coefficient of 0.75) and from measured [Na]_i. Results are expressed as mean ± SE. n, number of oocytes from 2-3 independent experiments. Statistics were performed by unpaired t-test referenced to values in rENaC-expressing oocytes. Statistical significance: NS, not significant; ∗∗∗, P < 0.001.