Table 2.

Apparent and real ENaC conductances (in μS) in rENaC/hCFTR-co-expressing oocytes measured with three different voltage gains

	No CFTR activation		Full CFTR activation
Voltage gain	Gapp	Greal	Gapp	Greal
1 k	55	62	25	67
4 k	62	65	52	68
10 k	61	62	59	68

In this example 2.8 ng rENaC-cRNA and 0.8 ng hCFTR-cRNA were injected and oocyte conductance was measured after 50 h of incubation; representative of four other experiments with low cRNA amounts. CFTR was activated by 0.5 mm IBMX + 10 μm forskolin. Apparent conductance (G_app) was determined as the current slope between −20 mV and +20 mV and real conductance (G_real) was determined as the current slope between the actually observed voltages, with −20 mV and +20 mV as target values in the voltage clamp protocol. Both G_app and G_real are given in μS. Configuration as in Fig. 1B with two bath electrodes and an estimated R_s of less than 200 Ω. Although in this example G_real is slightly larger during CFTR activation, ENaC seems significantly inhibited by CFTR activation when compared to G_app, obtained at a voltage gain of 1 k.