"THE ROLE OF PROSTAGLANDINS AND MAST CELLS IN THE MODULATION OF ACUTE ACID-INDUCED TRACHEAL CONTRACTION IN RAT"

Abstract

The exact role of the epithelial lining of the trachea in modulating the bronchial tone is controversial. The present study was an attempt to verify the role of both prostaglandins and mast cells in the acute phase of acid inspiration in rat. Four groups (n = 6) of N. Mari rats were employed. The first group was used as placebo control, and normal saline was injected. To the second group hydrochloric acid (25 µl) with pH of 1.3 was injected into the trachea through the criothyroid membrane. The third and fourth groups were pretreated for three consecutive days either with indomethacin (10 mg/Kg) or nebulized sodium cromoglycate (20 mg/Kg), 1 hour prior to installation of the acid. Three minutes after instillation of acid, the trachea was removed. The tracheal spirals were prepared and immediately suspended in an organ bath containing Tyrode’s solution. Dose response curves to acetylcholine (10-9 to 10-3M) were constructed. The results showed that the responses to acetylcholine in the acid treated trachea were significantly (P<0.01) reduced compared with the control saline treated trachea due to acute acid-induced tracheal contraction. Incubation with atropine, induced reduction of baseline tension and reversed the responses to acetylcholine. Both indomethacin and sodium cromoglycate, reversed the responses to acetylcholine and were in similar range as the control trachea. In conclusion, it seems that both prostaglandins and mast cells are important mediators in the acute phase of airway smooth muscle contraction following instillation of acid.