RELAXING ACTION OF VASOACTIVE INTESTINAL PEPTIDE (VIP) ON SMOOTH MUSCLE OF ISOLATED GUINEAPIG TRACHEA; ROLES OF EPITHELIAL CELLS

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Relaxing action of VIP on acethylcholine (Ach)-induced pre-contraction of smooth muscle of isolated guineapig trachea was examined in a condition with or without epithelium. The action was compared with those of isoproterenol and theophyline. Dose-response curve produced by Ach was also made after VIP (10-8M) was added into a organ bath before applying Ach.(1) VIP relaxed Ach-induced pre-contraction of guinea-pig trachea in a dose dependent manner. The action was more potent than those of theophylline and isoproterenol in molar basis.(2) Relaxing action of VIP, theophylline and isoproterenol on Ach-induced pre-contraction of the tracheal strip was attenuated by removing epithelium, indicating spontaneous synthesis of epithelium derived relaxing factor in the epithelial cells.(3) Inhibitory action of VIP against Ach-induced contraction of the guineapig trachea was not apparent, when VIP was added in the organ bath prior to Ach. This result indicated that VIP might be inactivated by neutral endopeptidase which was produced in epithelial cells after a certain period of time.
日本小児アレルギー学会の論文