Airway transepithelial electric potential in vivo: species and regional differences

A technique for measurement of transmural bioelectric potential difference (PD) in vivo was adapted for use in mammalian airways. PD was measured between a Ringer-perfused exploring bridge positioned on the airway furface and a reference Ringer-agar bridge in the subcutaneous space. The in vivo PD of canine trachea from 50 dogs was 30.8 +/- 9.5 (SD) mV, lumen negative, indistinguishable from the peak in vitro transmural PD of the excised canine trachea. Liquid junction potentials between bridge perfusate and tracheal liquid were negligible. The response pattern to drugs applied to the mucosal surface in vivo was similar to that observed in vitro. The PD in canine bronchi 3-6 cm distal to the carina were substantially lower. Tracheal PDs of rabbit (-23 mV), guinea pig (-8 mV), and rat (-14 mV) were higher than bronchial PDs of the same species. PD across airway epithelia can be accurately and reliably measured in vivo and the lower bronchial PD suggests regional differences in electrolyte transport and/or permeability.