Abstract

Objective: To investigate the relaxation mechanims of marmin on epithelium of guinea pig isolated trachea smooth muscle (TSM). Methods: The study was conducted using in vitro isolated-trachea experimental. The guinea pig isolated trachea were incubated in Krebs solution-containing organ bath and supplied with a mixed gas of O2:CO2 (95%:5%). Result: Removal of tracheal epithelium was associated with significant increases in the potencies of histamine and methacholine to contract guinea pig TSM. The pD2 value of histamine increased from 6.04依0.08 on epithelial-intact to 6.32依0.06 on epithelial-denuded (P<0.05). The pD2 value of methacholine also increased from 5.85依0.09 on epithelial-intact to 6.15依0.07 on epithelial-denuded (P<0.05). Marmin exhibited relaxation effects on TSM induced by methacholine (3伊10-5 mol/L) and histamine (3伊10-5 mol/L). Inhibition of prostaglandin E2 (PGE2) through incubation with indomethacin could reduce the relaxation effect of marmin (P<0.05) on methacholine- and histamine-induced contractions. However, no significant differenceswere shown in methylene blue, Nω-nitro-L-arginine (L-NNA) and propranolol-incubated TSM. Conclusions: The results suggest that marmin has relaxation effect on TSM which is epithelial-dependent through the release of PGE2. However, nitric oxide, cGMP and 毬 2-adrenergic-mediated relaxation were not involved.

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