The effect was similar with respect to proton dependent decreases in channel conductance as CF and CF/EK NaV1.5 show relatively similar effects at pH 7.0, 3% block in CF and 1% in CF/EK, when compared to the block at pH 6.0, 26% in CF and 37% in CF/EK. Here, SCN5A is linked to cystic fibrosis.