Ion transport across cat and ferret tracheal epithelia

Sheets of trachea from ferret and cat were mounted in Ussing chambers and continuously short circuited. Under resting conditions, in both the cat and ferret there was little or no Cl secretion, and Na absorption accounted for most of the short-circuit current (I(sc)). Ouabain (10^-4 M, serosal bath) reduced I(sc) to zero in 30-60 min. This decline was matched by a decrease in net Na absorption. Amiloride (10^-4 M, luminal bath) caused a significant decrease in I(sc) and conductance (G) in both species. Bumetanide (10^-4 M, serosal bath) had negligible effects on I(sc) and G. In both species, isoproterenol increased I(sc) by stimulating Cl secretion. Methacholine induced equal amounts of Na and Cl secretion, with little change in I(sc). In the cat, prostaglandins E₂ and F(2α) and bradykinin increased I(sc), responses which were abolished in Cl-free medium. In open-circuited cat tissues, Na flux from the serosal to mucosal side was measured simultaneously with the secretion of nondialyzable ³⁵S. Prostaglandins E₁, E₂, and F(2α), histamine, bradykinin, methacholine and isoproterenol all increased both Na and ³⁵S-mucin secretion.