| Summary: | 碩士 === 慈濟大學 === 藥理暨毒理學研究所 === 92 === To investigate the involvement of cholinesterase (ChE) in the modulation of the respiratory function, this study examined the distribution of ChE in swine airways and the influence of ChE in tracheal muscular contractions. Results showed that the ACh-induced tracheal smooth muscle contraction was decreased with the presence of epithelium, but the contractile response to carbachol was not altered. Moreover, the inhibitory effect of epithelium on ACh-elicited muscle contraction was associated with the increase in AChE activity derived from epithelium, which was reversed by acetylcholinesterase inhibitor, neostigamine. Contrarily, the ACh metabolite choline inhibited the activity of epithelial AChE, which was recovered by α7 nicotinic receptor antagonist α7-bungarotoxin. The muscarinic receptor antagonists such as pirenzepine, gallamine, and atropine blocked the ACh-induced increases in AChE activity. The distributions of AChE in airway trachea, including epithelium, smooth muscle and nerve bundles were observed in histochemical staining. The expressions of AChE and BChE stimulated by ACh were enhanced in tracheal slices and primary cultures of tracheal epithelium. Moreover, the ACh-induced increases in ChE activities were found in the release and cell extracts of primary cultured epithelium. However the protein levels of AChE were not affected. In conclusion, the distribution of ChEs exists in airways unrelated to neuronal location, while the ChE activity is modulated by cholinergic stimulation. Furthermore, airway epithelium has the ability to inhibit muscle contraction in response to cholinergic stimulation, resulting from the enhancement of epithelium-derived ChE activity through the activation of muscarinic receptors.
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