Characterization and comparison of ion transport across sheep and human airway epithelium

This study aimed to assess the suitability of sheep tracheal epithelium as a model for studies of human airway ion transport. Ovine and human airway epithelium were mounted in Ussing chambers under short circuit conditions. Bumetanide (100 microM) reduced short-circuit current (Isc) by a mean of 21.3% +/- SEM 2.0, n = 8, in sheep, and 30.4% +/- 9.7, n = 3, in human airway epithelium. Acetazolamide (100 microM) decreased Isc by 10.6% +/- 1.2, n = 18, in sheep, and 5.8% +/- 2.9, n = 3, in human airways. Phloridzin (200 microM) reduced Isc by 4.7% +/- 0.8, n = 7, and 3.1% +/- 5.1, n = 3 in sheep and human tissue respectively. Amiloride (100 microM) decreased Isc by 42.9% +/- 3.5, n = 12, in sheep airways, whilst bathing the mucosal surface with Na(+)-free solutions reduced Isc by 67.4% +/- 4.2, n = 18. The sequential addition of acetazolamide, bumetanide, phloridzin, amiloride and mucosal Na(+)-free solutions totally inhibited the basal Isc in both sheep and human tissues, suggesting that Cl- and HCO3- secretion, Na(+)-glucose co-transport and amiloride-sensitive and -insensitive Na+ absorption contribute to the Isc. The similarities between the species suggest that sheep tracheal epithelium is a useful model for basal studies of airway ion transport, and may prove a valuable tool for further regulatory studies.