Vol. 286, Issue 2, 772-779, August 1998

Epoxygenase Metabolites of Arachidonic Acid Affect Electrophysiologic Properties of Rat Tracheal Epithelial Cells¹

Jorge M. S. Pascual , Andrew McKenzie, James R. Yankaskas, John R. Falck and Darryl C. Zeldin

Laboratory of Pulmonary Pathobiology (J.M.S.P., D.C.Z.), National Institute of Environmental Health Sciences, Research Triangle Park; Division of Pulmonary and Critical Care Medicine (J.M.S.P.), Duke University Medical Center, Durham; Division of Pulmonary Diseases (J.R.Y.), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina and Department of Molecular Genetics (J.R.F.), University of Texas Southwestern Medical Center, Dallas, Texas

Epoxyeicosatrienoic acids (EETs) and dihydroxyeicosatrienoic acids, products of the cytochrome P450 arachidonic acid epoxygenase pathway, have been shown to affect electrolyte transport in the kidney; however, the effects of these compounds on airway epithelial ion transport have not been investigated. Intact rat tracheas and primary cultures of rat tracheal epithelial cells were mounted in Ussing chambers to monitor changes in transepithelial voltage (Vt), short circuit current (Isc) and electrical resistance (Rt), with or without the addition of increasing concentrations (10⁹-10⁶ M) of arachidonic acid, each of the four regioisomeric EETs and each of the corresponding dihydroxyeicosatrienoic acids. In intact tracheas, 11,12-EET caused dose-dependent decreases in Vt and Isc (Vt = 0.4 ± 0.1 mV, Isc = 16.9 ± 5.4 µA/cm² at 10⁶ M, P < .05 vs. vehicle), whereas changes in Rt were not significantly different than vehicle alone. 11,12-dihydroxyeicosatrienoic acid caused less impressive decreases in Vt and Isc, although arachidonic acid and the other compounds tested were without significant effects. 11,12-EET induced similar changes in cultured tracheal epithelial cell electrical parameters at concentrations as low as 10⁹ M. The effects of 11,12-EET were highly stereoselective, with activity limited to 11(R),12(S)-EET, the least abundant rat lung enantiomer. Pretreatment with amiloride or mucosal exposure to sodium free media did not significantly alter the 11,12-EET-induced changes in Vt. In contrast, pretreatment with bumetanide abolished the 11,12-EET electrophysiologic effects, suggesting that these effects may be mediated through inhibition of a chloride conductive pathway. We conclude that arachidonic acid epoxygenase metabolites cause significant changes in rat airway electrical parameters and may be involved in the control of lung fluid and electrolyte transport.