Effects of sobrerol treatment on macromolecule secretion, ion and water fluxes in sheep trachea.

We studied the effects of sobrerol treatment on airway mucus secretion. Normal sheep and sheep with airways sensitized to Ascaris suum antigen were treated in vivo with sobrerol, 1 mg.kg-1 i.m., twice a day for five days. Composition and secretion of mucus macromolecules, and fluxes of ions and water were subsequently measured in tracheal tissues in vitro, and were compared to values from untreated (normal and sensitized) sheep. Macromolecules were radiolabelled with 35SO4 and 3H-threonine and we measured the secretion of macromolecule-bound radiolabel on to the mucosa. We also measured secretion of total protein and of sialic acid. Unidirectional fluxes of Cl-, Na+ and water were measured with radioactive tracers. Net fluxes were calculated from appropriately paired tissues. Sobrerol treatment decreased total protein secretion in both normal and sensitized sheep. Specifically, it decreased secretion of sialylated but not sulphated macromolecules. Sobrerol had no effect on tracheal ion or water fluxes in normal sheep, but in sensitized sheep it significantly decreased net Na+ absorption and induced secretion of water. These changes are likely to alter the physical properties of the mucus, and may alter its transportability by airway cilia and/or by gas-liquid two-phase flow.