Role of prostaglandins in contractile activity of the ampulla of the rabbit oviduct

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Abstract
Contractile activity of the ampulla of rabbit oviducts removed 24 h after an ovulating injection was studied in vitro. Spontaneous activity, field-stimulated activity, and response to phenylephrine were studied in normal, reversed, and scraped (endosalpinx removed) sections of tissues in the presence or absence of inhibitors of prostaglandin synthetase (8 or 51 micrograms/ml indomethacin or 10 or 100 micrograms/ml 5,8,11,14-eicosatetraynoic acid (ETA)). The effects of in vivo treatment with 10 mg/kg of indomethacin on the same responses were examined. Scraped tissues produced more prostaglandin E and F (measured by radioimmunoassay) than did normal tissues, and this production was suppressed by 10 micrograms/ml of indomethacin or 100 micrograms/ml of ETA. Production of prostaglandin by normal tissues was not depressed by these compounds in vitro, but was significantly reduced by pretreatment of the animals with indomethacin in vivo. In the absence of the endosalpinx, the myosalpinx exhibited spontaneous activity and responded to field stimulation and phenylephrine. Scraped and reversed tissues, however, showed a faster decline in response to field stimulation than normal tissues, and this was due to the traumatization. By contrast, traumatization increased the sensitivity of the tissue to respond to phenylephrine. Inhibition of prostaglandin synthetase by low doses of indomethacin or ETA prevented desensitization of the tissue to field stimulation, but this desensitization was little affected by the higher doses of indomethacin in vitro or in vivo. ETA did not affect the phenylephrine dose-response curves and nor did 8 micrograms/ml of indomethacin, whereas the high dose was inhibitory. Spontaneous activity was only affected by the in vivo pretreatment with indomethacin, which prevented the decline in activity of scraped tissue with time.