Guinea‐pig Tracheal Epithelial Cell (EC) Shrinkage Induced by Hyperosmolar Challenge

Abstract

Hyperventilation during exercise is thought to increase the osmolarity of airway surface liquid. Hyperosmolar challenge of EC with mucosal D-mannitol (D-M) in methacholine (MCh)-contracted guinea-pig isolated, perfused trachea elicits smooth muscle relaxation mediated by epithelium-derived relaxing factor (EpDRF). To understand the relationship between EpDRF release and hyperosmolarity-induced changes in cell volume (CV), we examined CV changes in response to challenge of EC with 120 mosM D-M. EC were isolated from tracheas by protease digestion (2%; 1 h) and suspended in Krebs-Henseleit solution. Suspended EC remained viable for more than 5 h as indicated by active beating of cilia and exclusion of trypan blue (90 to 95%). CV was measured using a cell sizer. D-M induced a rapid decrease in CV (~9% shrinkage) during the first minute. The peak CV decrease occurred between 3 to 5 min (~22% shrinkage). No increase in CV was observed during the next 5 h. The results indicate that hyperosmolar conditions which cause EpDRF-mediated relaxation also evoke EC shrinkage. The rapid onset of the relaxation and CV responses could suggest that signaling pathways are shared. 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.