Differential effects of epithelium removal on the responsiveness of guinea-pig tracheal smooth muscle to bronchoconstrictors.
Hay-DWP; Farmer-SG; Raeburn-D; Muccitelli-RM; Wilson-KA; Fedan-JS
Br J Pharmacol 1987 Oct; 92(2):381-388
The effect of epithelium removal on the responsiveness of guinea-pig tracheal smooth muscle to bronchoconstrictors was studied in-vitro. Tracheae were removed from adult male Hartley-guinea-pigs and English-short-hair-guinea-pigs, some of which had been sensitized with ovalbumin. The epithelium was removed mechanically from alternate strips. The leukotrienes LTC4, LTD4 and LTE4, the potent bronchoconstrictor 5-hydroxytryptamine (5HT), and the thromboxane mimetic U-44069 were added to the bathing solution and the effects on contractile reactivity of the muscle tissues were investigated. In some cases, indomethacin was added before the experiment. In control tissues, removing the epithelium caused a significant increase in sensitivity to LTC4 and LTD4, whereas contractions induced by LTE4 were not affected. Similar effects were seen in tissues from ovalbumin treated animals. Indomethacin increased the sensitivity of the intact trachea to LTC4; sensitivity was not affected by removing the epithelium. Sensitivity to LTD4 with or without the epithelium was not affected. Indomethacin decreased the sensitivity of the tracheal muscle to LTE4, regardless of epithelial integrity. The responses induced by 5HT or U-44069 were similar in the presence or absence of the epithelium in control or ovalbumin sensitized tissues. The authors conclude that the effects of epithelium removal on the responsiveness of airway smooth muscle reflect differential influences on epithelium derived modulating factors, rather than just the loss of a diffusion barrier.
NIOSH-Author; In-vitro-studies; Laboratory-animals; Muscle-contraction; Drugs; Muscle-function; Bronchial-asthma; Pulmonary-system-disorders
British Journal of Pharmacology