Relationship between endothelin‐1 binding site densities and constrictor activities in human and animal airway smooth muscle

Abstract

1Endothelin-1 (ET-1) binding site densities and constrictor activities were compared in airway smooth muscle preparations of human, guinea-pig, rat and mouse. 2 The mean contractile response to 0.3 pM ET-1 (measured as the % maximum response to 10puM carbachol, % C,.., + s.e.mean) and the mean concentration of ET-1 producing 30% C,.,. (95% confidence limits) were respectively; 85.9 + 5.4% and 3.4nM (2.4-5.0) for mouse trachea (n = 11), 88.8 + 4.7% and 18.2nM (11.2-25.2) for rat trachea (n = 6), 71.0 + 7.1% and 35.2 nm (5.4-231) for human bronchus (n = 3), and 32.3 + 3.0% and 241 nm (125-460) for guinea-pig trachea (n = 6). .5 amol mm-2) > mouse trachea (28.7 + 2.6 amol mm 2) > guinea-pig trachea (8.3 + 1.8 amol mm-2). 5 A positive relationship between [125I]-ET-1 binding site density and ET-1 constrictor activity was observed in airway smooth muscle preparations from rat, human and guinea-pig. The greater sensitivity of mouse trachea to the constrictor actions of ET-1 was not dependent on the release of cyclo-oxygenaseor epithelium-derived constrictor substances, but may have been due to an inter-species difference in the receptor-effector system for ET-1.

Pharmacological modulation of endothelin‐induced contraction of guinea‐pig isolated airways and thromboxane release

“…The reasons for this discrepancy are unclear at present, but it might be attributed to differences in tissue preparations (use of tracheal rings or segments in the previous studies versus zig-zag strips in the experiments of Maggi et al, 1989, and helical strips in the present study) and/or to differences in the experimental protocols (lower initial load, different incubation buffers and exposure of the tissues to high concentrations of KCI or carbachol before studying the effects of ET-1 in the previous experiments) in addition to the different strains of guinea-pig used. ET-1 appeared to be more potent in our tracheal preparations (estimated EC50 24.4nM) than was previously reported (estimated EC50 values of 50-60nM in the experiments of Hay, 1990 andHenry et al, 1990). Another possibility might be that inhibition of prostaglandin synthesis by indomethacin is heterogeneous in lung tissue as was previously reported for the kidney (Attallah & Stahl, 1980).…”

“…Analysis of the incubation medium showed that the basal release of TXA2 was in the 150-300pg range (Table 1) (0) (1-10nM), whereas no significant inhibition was seen at higher ET-1 concentrations (50-300nM) in the guinea-pig trachea in vitro (Maggi et al, 1989). Recently, indomethacin (5puM) has been reported to enhance the myotropic action of ET-1 in the guinea-pig trachea (Hay, 1990;Henry et al, 1990). The reasons for this discrepancy are unclear at present, but it might be attributed to differences in tissue preparations (use of tracheal rings or segments in the previous studies versus zig-zag strips in the experiments of Maggi et al, 1989, and helical strips in the present study) and/or to differences in the experimental protocols (lower initial load, different incubation buffers and exposure of the tissues to high concentrations of KCI or carbachol before studying the effects of ET-1 in the previous experiments) in addition to the different strains of guinea-pig used.…”

Inhibitory effects of nordihydroguaiaretic acid on ETA‐receptor‐mediated contractions to endothelin‐1 in rat trachea

“…Selective inhibition of ET-J-induced contractions by NDGA As shown previously (Henry et al 1990b;1992 required to induce a contraction of 50% Cmax was 29 nM (95% confidence limits, 17-51 nM, n = 6). ET-1-induced contractions were concentration-dependently inhibited by NDGA ( Figure la).…”

“…ET-1 initiates contraction by guinea-pig (Hay, 1992). In addition, recent autoradiographic, stimulating high affinity receptors located on the surface biochemical and functional studies indicate that ET-1-membrane of the airway smooth muscle cells (Turner et al, induced contractions in rat trachea appear to bc mediated by 1989; Henry et al, 1990b;Mattoli et al, 1991). At least two both ETA and ETB receptor-effector systems (Henry, 1993).…”

“…Autoradiographs of ['251]-ET-1 binding to rat tracheal sections were prepared as described previously (Henry et al, 1990b (Henry et al, 1990a). Four separate fields (3 over smooth muscle and one background measurement over a non-tissue area) were viewed from each tracheal section and quadruplicate total and non-specific slides were analysed.…”