Abstract
The effects of several mediators including prostanoids, neuromediators, bioactive peptides and leukotrienes were investigated on the trachea, upper bronchi, lower bronchi and lung parenchyma of selected strains of mice mounted in a cascade superfusion system. The upper airways (trachea, upper bronchi) responded with greater maxima than lower airways (lower bronchi, lung parenchyma). Acetylcholine, carbachol, serotonin and 9,11-dideoxy-9α,11α-epoxymethano-prostaglandin F 2α (U-44069) contracted the mouse airways (acetylcholine>carbachol>serotonin≥U-44069). However, the rank order of potency for these compounds was U-44069>carbachol>serotonin≥acetylcholine. Prostaglandins E 2, F 2α and D 2 relaxed the carbachol precontracted isolated mouse airways achieving >90% relaxation in some cases. The rank order of potency for the prostaglandins was E 2≥F 2α>D 2 with the exception of the lower bronchi on which prostaglandins had the following order of potency: F 2α≥E 2>D 2. The effects of prostaglandins were similar in four commonly used strains of mice (CD-1, BALB/c, C57BL/c6 and C3H) with some variations in efficacy. Iloprost was a weak mouse airway relaxant. It had the greatest effect on the trachea and bronchi of BALB/c and C57BL/c6 mice, whereas it had little or no effect on the airways of the CD-1 and C3H mouse strains. Vasoactive intestinal peptide potently relaxed the carbachol and precontracted the mouse trachea and bronchi. However, vasopressin, another bioactive peptide, potently and efficaciously contracted the mouse trachea and upper bronchi but had little effect on the lower bronchi. Vasopressin was the most potent and efficacious contractile agonist tested in this study. Contractions were observed with endothelins-1, -2 and -3 on mouse trachea and bronchi, but marked tachyphylaxis was present. Sarafotoxin s6c followed the same pattern suggesting the presence of endothelin ET B receptors on the mouse airways. Of all leukotrienes assayed (B 4, C 4, D 4 and E 4) only leukotriene C 4 weakly contracted the mouse trachea and upper bronchi, but tachyphylaxis was most evident.
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