Modulation of equine tracheal smooth muscle contractility by epithelial-derived and cyclooxygenase metabolites.
Abstract: The role of epithelium in the modulation of contractile responses to electrical field stimulation (EFS), acetylcholine (ACh), and KCl were studied in vitro in strips of equine tracheal smooth muscle (TSM). EFS with 0.5 ms pulses of voltage (70 V) resulted in frequency dependent contractions of equine TSM that were sensitive to tetrodotoxin (TTX) and atropine. In TSM without epithelium, preincubation with indomethacin significantly potentiated contractile responses to EFS. The potentiating effect of indomethacin on EFS contractions was abolished by the addition of 3 nM prostaglandin E2 (PGE2). ACh and KCl cumulative concentration-response curves were shifted to the left by removal of epithelium from equine TSM strips with a significant decrease in the 50% effective concentration (EC50) for both ACh and KCl. The mean EC50 (+/- SE) for ACh in TSM without epithelium was 0.51 +/- 0.09 microM vs 4.30 +/- 1.03 microM in TSM with epithelium. Similarly, the mean EC50 (+/- SE) for KCl in TSM without epithelium was 22.20 +/- 2.61 mM vs 32.35 +/- 2.66 mM in TSM with epithelium. The addition of indomethacin (3 microM) had no effect on the ACh concentration-response curves in TSM strips with or without epithelium. Our results suggest that in the equine airway there is (1) an epithelial-derived relaxant factor that modulates tracheal smooth muscle contractility postsynaptically, and (2) a nonepithelial-derived inhibitory factor, possibly PGE2, that modulates ACh release from nerves presynaptically.
Publication Date: 1991-04-01 PubMed ID: 1906628DOI: 10.1016/0034-5687(91)90022-bGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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The research paper explores how the epithelium, or the tissue lining the trachea, influences the contractility of tracheal smooth muscle in horses. The study finds that factors derived from the epithelium and cyclooxygenase metabolites can modulate the contraction responses in this muscle to specific stimuli.
Methodology
- The scientists investigated the role of the epithelium in modulating contractile responses to electrical field stimulation (EFS), acetylcholine (ACh), and potassium chloride (KCl) in the tracheal smooth muscle (TSM) of horses.
- In vitro experiments were carried out on strips of equine TSM. The contractions mediated by EFS were found to be dependent on frequency, and were influenced by tetrodotoxin (TTX) and atropine.
Findings
- The research showed that if the epithelium was removed from the TSM, response to EFS increased upon preincubation with indomethacin, a non-steroidal anti-inflammatory drug (NSAID). However, this increased contractility was abolished by prostaglandin E2 (PGE2).
- ACh and KCl, two agents known to cause contraction in smooth muscles, also showed changed effects upon removal of the epithelium. The concentrations required to induce 50% of the maximum response (EC50) for both agents decreased significantly upon removal of the epithelium, suggesting that the epithelium has a modulatory effect on muscle contractility responses to ACh and KCl.
Conclusions
- The results suggest that within the equine airway, there exists an epithelial-derived factor that regulates (relaxes) tracheal smooth muscle contractility post-synaptically. This occurs after the signal has been transmitted across the synapse, the junction between nerves.
- The study also hints at the existence of a non-epithelial-derived inhibitory factor, possibly PGE2, that modulates the release of ACh from nerves before the signal is transmitted, known as presynaptic modulation.
Implications
- This research provides insight into how contractility of tracheal smooth muscle is regulated in horses. It could have implications for understanding and treating disorders related to muscle contractility in the equine respiratory system.
Cite This Article
APA
Tessier GJ, Lackner PA, O'Grady SM, Kannan MS.
(1991).
Modulation of equine tracheal smooth muscle contractility by epithelial-derived and cyclooxygenase metabolites.
Respir Physiol, 84(1), 105-114.
https://doi.org/10.1016/0034-5687(91)90022-b Publication
Researcher Affiliations
- Department of Veterinary Biology, University of Minnesota, St Paul 55108.
MeSH Terms
- Acetylcholine / pharmacology
- Animals
- Arachidonic Acids / pharmacology
- Biological Factors / physiology
- Cyclooxygenase Inhibitors
- Dinoprostone / pharmacology
- Electric Stimulation
- Horses
- Indomethacin / pharmacology
- Muscle Contraction / drug effects
- Muscle, Smooth / drug effects
- Muscle, Smooth / enzymology
- Muscle, Smooth / physiology
- Potassium Chloride / pharmacology
- Prostaglandin-Endoperoxide Synthases / metabolism
- Trachea / drug effects
- Trachea / enzymology
- Trachea / physiology
Citations
This article has been cited 1 times.- Kiyota T, Sugahara K, Nakamura M, Matsuda F, Terasaki H, Morioka T. Effects of halothane and enflurane on epithelium-dependent contraction and ion transport of canine tracheal epithelium.. J Anesth 1994 Dec;8(4):455-460.
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