Effects of Na + and Cl − Channel Blockers on Guinea‐pig (GP) Isolated Tracheal epithelial cell (EC) shrinkage in response to hyperosmolar challenge

Abstract

In GP trachea that are precontracted with methacholine (MCh; 3H10−7 M), hyperosmolar D-mannitol (D-M) induces changes in epithelial Na+ and ClΓ transport and smooth muscle relaxation mediated by epithelium-derived relaxing factor (EpDRF). We examined the effects of sequentially-added ion channel blockers, MCh and D-M (30 mosM) on EC cell volume (CV) changes in ECs isolated enzymatically (2% protease, 1 h) from GP-trachea and suspended in Krebs-Henseleit solution, under conditions in which these agents are used in the isolated, perfused trachea preparation to examine D-M-induced EpDRF release. CV was measured with a cell sizer. D-M elicited shrinkage of EC (~15 %) under conditions in which it caused EpDRF-mediated relaxation. The Na+ channel blocker, amiloride (A; 10−4 M), did not affect EC CV. MCh had no effect on CV (±A). Shrinkage stimulated by D-M was unaffected by A. On the other hand, incubation with the ClΓ blocker, DIDS (10−4 M), resulted in an immediate and prolonged decrease in CV (~9%). Again, MCh had no effect on CV (±DIDS). However, in the presence of DIDS the CV decrease in response to D-M was diminished. Thus, the inhibitory effect of A on EpDRF release is not due to an effect on EC shrinkage, whereas the inhibitory effect of DIDS on EpDRF release may be linked to the decrease in the CV response. The findings and conclusions in this abstract have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination of policy. Funded by NIOSH.