Prostaglandins and myogenic control of tension in lower esophageal sphincter |
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Authors: | EE Daniel J Crankshaw S Sarna |
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Institution: | Departments of Neurosciences, Surgery and Electrical BioEngineering McMaster University 1200 Main Street West Hamilton, Ontario Canada L8S 4J9 |
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Abstract: | Active tension is produced by the lower esophageal sphincter (LES) of North American opossum by a myogenic mechanism. Strips of LES, but not those from the esophageal body, contracted to prostaglandin (PG)F2α, stable expoxymethano derivatives of PGH2 and to thromboxane B2. Stable endoperoxides were more than 500 times more potent than PGF2α. PGI2 and 6-keto PGF1α were weak relaxants of LES strips. LES strips transformed arachidonic acid into contractile substances. This transformation was prevented by agents which interfere with PG synthesis by inhibiting cyclo-oxygenase indomethacin (IDM), 5,8,11,14-eicosatetraynoic acid (ETA) or thromboxane synthetase imidazole]. Tranylcypromine 500 μg/ml also inhibited contractions to arachidonic acid. These agents also reduced muscle tone, so that endogenous PG formation may contribute to active tension in the LES. ETA and IDM increased tone before inhibiting it, and this effect was prevented by prior treatment with ETA or imidazole. There may also be an endogenous PG which inhibits LES tone. The possibility that this may be PGI2 is discussed. |
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Keywords: | Prostaglandin Receptors Endoperoxides Lower Esophageal Sphincter Esophageal Body |
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