The guinea‐pig isolated bronchus for the in vitro study of small calibre airway reactivity

Abstract

1 Small calibre airway reactivity to different contractile and relaxant agents was tested in vitro using small segments (about 1 mm long and 0.2 mm in internal diameter) of guinea-pig isolated intralobular bronchi. 2 EC50 values of, and maximal contractile responses to contractile agents were as follows (mean ± s.e.mean, n = 6): acetylcholine 13.6 ± 2.6 gM and 1140 ± 80 mg; histamine 5.2 ± 0.7 JM and 1094 ± 95 mg; 5-hydroxytryptamine (5-HT) 0.7 ± 0.1 gM and 595 ± 61 mg; prostaglandin Fu (PGF2.)8.8 ± 1.2 tM and 1100±88mg; tetraethylammonium 2.9±0.3mM and 1055±94mg; KC1 14.6 ± 0.5mM and 965 ± 81 mg.3 EC50 values of, and maximal relaxant responses to P-adrenoceptor stimulants on preparations precontracted with acetylcholine (1.4 x 10-4M) were: isoprenaline 0.40 ± 0.5 JM and 782 ± 65 mg, n = 18; salbutamol 0.19 ± 0.02 JM and 494 ± 55mg, n = 5; terbutaline 0.87 ± 0.18 gM and 263 ± 40mg n = 5; fenoterol 0.06 ± 0.02 JM and 722 ± 47mg, n = 5; adrenaline 0.71 ± 0.13 JM and 653 ± 62mg, n = 5; noradrenaline 10.8 ± 0.9 JM and 566 ± 97mg, n = 5.4 Differences in the maximal relaxant effects between the P-adrenoceptor stimulants showed that the preparation utilized is a relevant model for assessment of the intrinsic activity of these drugs.5 The high ratio (about 180) of the ECm for noradrenaline (pi-adrenoceptor agonist) to that for fenoterol (f2-adrenoceptor agonist), and the lack of effect of prenalterol (P1-adrenoceptor agonist) suggested that P2-adrenoceptors are preferentially involved in the relaxant activity of P-adrenoceptor stimulants in this preparation.

Bronchodilatation of guinea‐pig perfused bronchioles induced by the H3‐receptor for histamine: role of epithelium

“…In the present study, preparations contracted when histamine, acetylcholine and K+ were applied. For these drugs, the maximum effects and pD2 ( Figure 3; Table 1) were obtained over a similar range of concentrations to those reported by other authors who worked with guinea-pig but with different airways generations and various methods (Advenier & Freslon, 1985;Farmer et al, 1986;Touvay et al, 1986;Braunstein et al, 1988). The experimental system described in our study seems to be of a similar nature to that used by Munakata et al (1988) but there are some differences which could be important.…”

Bronchodilator action of an agonist for histamine H3-receptors in guinea pig perfused bronchioles and lung parenchymal strips

“…For these drugs the maximum effects and ECs0 were obtained at a similar range of concentrations to those reported by other authors who have worked on guinea pig airways using various methods [1,8,33,35].…”

Bronchospasmolytic Effects of Ru 42173

“…In this set of experiments RU 42173 and salbutamol behaved as partial agonists. It must be noted that all selective beta-stimulants are partial agonists, and the only full agonists are isoprenaline, adrenaline, and noradrenaline (Advenier and Freslon, 1985). When tested against acetylcholine on isolated human bronchi, RU 42 173 showed a relaxant activity similar to that of salbutamol.…”

“…Small bronchi, 0.2-mm ID, were prepared according to the method described by Advenier and Freslon (1985). With this method, male Hartley guinea pigs weighing from 250 to 350 g were anaesthetized with urethane and mechanically ventilated.…”