title: Subthreshold concentration of endothelin-1-enhanced, capsaicin-induced bronchoconstriction in anaesthetized guinea-pigs.
abstract: An increasing number of studies have been performed to address a possible role for endothelin-1 (ET-1) as a significant mediator in asthma. However, the effects of subthreshold concentrations of ET-1, which cannot elicit bronchial smooth muscle contraction itself, in asthma has yet to be determined. This study determined these effects of ET-1 on capsaicin-induced bronchoconstriction in anaesthetized guinea-pigs. Aerosolized ET-1 administered at doses of 10(-9) M and higher induced a dose-dependent increase in pulmonary resistance, but ET-1 at 10(-10) M did not have any bronchoconstrictive effect. However, this subthreshold concentration of ET-1 potentiated capsaicin-induced bronchoconstriction. In addition, the potentiation of capsaicin-induced bronchoconstriction by this subthreshold concentration of ET-1 was completely abolished by BQ788 (ET(B) receptor antagonist), but not BQ123 (ET(A) receptor antagonists). Immunoreactive substance P (SP) levels in bronchoalveolar lavage fluid after capsaicin administration were significantly higher than those after solvent administration. However, ET-1 alone did not significantly stimulate immunoreactive SP release and ET-1 (10(-10) M) did not potentiate capsaicin-induced immunoreactive SP release. In contrast, ET-1 (10(-10) M) potentiated exogenous neurokinin A- and SP-induced bronchoconstriction. These findings suggest that a subthreshold concentration of endothelin-1 does not potentiate the tachykinin release induced by capsaicin but the airway smooth muscle contraction through endothelin-B receptors.
authors.affiliation: First Dept of Internal Medicine, Osaka City University Medical School, Osaka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kanazawa
authors.forename: H
authors.initials: H
authors.lastname: Fujiwara
authors.forename: K
authors.initials: K
authors.lastname: Hirata
authors.forename: J
authors.initials: J
authors.lastname: Yoshikawa
mesh_terms: D000336:Aerosols; D000403:Airway Resistance / Q000187:drug effects; D000758:Anesthesia; D000818:Animals; D001249:Asthma / Q000503:physiopathology; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D016084:Bronchoconstriction / Q000187:drug effects*; D002211:Capsaicin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology* / Q000502:physiology; D006168:Guinea Pigs; D008297:Male; D015288:Neurokinin A / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D013373:Substance P / Q000032:analysis / Q000494:pharmacology
chemical_list: D000336:Aerosols; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010880:Piperidines; D013373:Substance P; C086539:BQ 788; D015288:Neurokinin A; D002211:Capsaicin; C072247:cyclo(Trp-Asp-Pro-Val-Leu)