Electrophysiological properties of guinea pig tracheal epithelium determined by cable analysis

Electrophysiological characteristics of guinea pig tracheae were measured in vitro using an adaptation of cable analysis. This method allowed the repeated measurement of luminal diameter and epithelial electrical potential, resistance, and short-circuit current (Isc) during treatments known to affect smooth muscle contraction and epithelial ion transport. Stable values taken 3 h after mounting were as follows: diameter, 2.27 +/- 0.10 mm; potential, -28.3 +/- 2.3 mV; resistance, 327 +/- 30 omega.cm2; and Isc, 91.2 +/- 6.8 microA/cm2. These electrophysiological results are comparable to reported values for other species. However, the resistance and potential obtained in this study were larger than those previously reported for the guinea pig. Tracheal diameter was decreased 15% by methacholine and was increased 43% by subsequent isoproterenol treatment. Isoproterenol caused a small but significant increase in Isc when this quantity was normalized to tracheal length rather than to the apparent surface area. In contrast, apical amiloride decreased Isc by 51% and did not change diameter. These data validate this implementation of cable analysis, demonstrate that sodium absorption is the predominant mechanism of active ion transport by guinea pig tracheal epithelium, and indicate that this tissue has little capacity for stimulated chloride secretion.