Effect of the airway epithelium on the contraction of rat isolated trachea under conditions of low temperature.
BACKGROUND
The exposure of the airways to low temperature (LT) is a well-known trigger of bronchoconstriction and asthma. However, the mechanisms involved in this response are not well understood. In particular, the specific role of the airway epithelium in the response to LT has not been well established.


OBJECTIVE
The purpose of this work is to study the regulatory role of the airway epithelium in the contractile response of the rat trachea under conditions of LT.


METHODS
Isolated rat tracheas were stimulated with acetylcholine (ACH) at 37 and 18 degrees C, and dose-response curves were generated in epithelium-intact or epithelium-denuded conditions. EC(50) and E(max) were determined under these conditions.


RESULTS
Epithelium denudation at 37 degrees C, increases the tracheal sensitivity to ACH, (EC(50) from 5.9 to 2.6 microM, p = 0. 003). The effects of denudation were even more pronounced at 18 degrees C. E(max) was significantly decreased under these conditions. Exposure of intact tracheas to 18 degrees C also produced a significant increase in tracheal sensitivity (EC(50) from 5.9 to 1.5 microM, p = 0.0004), although no changes in E(max) were noted.


CONCLUSIONS
These results strongly suggest that the airway epithelium diminishes the sensitivity of the airway smooth muscle to ACH at 37 and 18 degrees C, and that it is also needed to observe the maximal contractile response under LT conditions. Therefore, the spasmogenic effect of low temperature is significantly potentiated by the absence of airway epithelium.
Department of Physiology, University of Puerto Rico School of Medicine, San Juan, P.R., Puerto Rico, USA. gonzlop@coqui.net
O
O
González
G E
GE
Santacana
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D003080:Cold Temperature; D004305:Dose-Response Relationship, Drug; D004848:Epithelium / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014132:Trachea / Q000187:drug effects / Q000502:physiology*
D000109:Acetylcholine