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AIM:To study the effect of progesterone on contractileactivity of isolated gastric strips in rats.METHODS:Wistar rats were sacrificed to remove wholestomach.Then,the stomach was opened and the mucosallayer was removed.Parellel to either the circular or thelongitudial fibers,muscle strips were cut from fundus,body,antrum and pylorus.Each muscle strip was suspended in atissue chamber containing 5 mL Krebs solution.Then themotility of gastric strips in tissue chambers was simultaneouslyrecorded.The preparations were subjected to 1 g load tensionand washed with 5 ml Krebs solution every 20 min.After1h equilibration,progesterone or antagonists were addedin the tissue chamber separately.The antagonists wereadded 3 min before using progesterone(50 μmol·L~(-1)).RESULTS:Progesterone decreased the resting tension offundus and body longitudinal muscle(LM)(P<0.05).Itinhibited the mean contractile amplitude of body and antrumLM and circular muscle(CM),and the motility index of pyloricCM(P<0.05).The inhibition of progesterone on the meancontractile amplitude could be partially blocked byphentolamine in LM of the stomach body(the meancontractile amplitude of body LM decreased from -7.5±5.5to -5.2±4.5 P<0.01),and by phentolamine or indomethacinin CM of body(The inhibition of progesterone on the meancontractile amplitude of body CM decreased from -5.6±3.0to -3.6±2.7 by phentolamine and from -5.6±3.0 to -3.5±2.5by indomethacin,P<0.01).Hexamethonium,propranolol andL-NNA(inhibitor of NO synthetase)didn’t affect the actionof progesterone(P>0.05).CONCLUSION:The study suggested that progesterone caninhibit the contractile activity of isolated gastric strips in ratsand the mechanism seems to be a direct one except thatthe action on gastric body is mediated through prostaglandinand adrenergic α receptor partly.
AIM: To study the effect of progesterone on contractileactivity of isolated gastric strips in rats. METHODS: Wistar rats were sacrificed to remove whole body.Then, the stomach was opened and the mucosallayer was removed. Parellel to either the circular or thelongitudinal fibers, muscle strips were cut from fundus, body, antrum and pylorus. Each muscle strips were suspended in at room temperature containing 5 mL Krebs solution. They were transferred to gastric strips in tissue chambers was simultaneously recoded. The preparations were subjected to 1 g load tension and washed with 5 ml Krebs solution every 20 min. After 1h equilibration, progesterone or antagonists were addedin the tissue chamber separately. The antagonists wereadded 3 min before using progesterone (50 μmol·L -1). RESULTS: Progesterone decreased the resting tension offundus and body longitudinal muscle (LM) (P <0.05) .Itinhibited the mean contractile amplitude of body and antrumLM and circular muscle (CM), and the motility index of pyloricCM (P <0.05) .T he inhibition of progesterone on the meancontractile amplitude could could be partially blocked byphentolamine in LM of the stomach body (the meancontractile amplitude of body LM decreased from -7.5 ± 5.5to -5.2 ± 4.5p <0.01), and by phentolamine or indomethacinin CM of body (The inhibition of progesterone on the mean contractile amplitude of body CM decreased from -5.6 ± 3.0 to -3.6 ± 2.7 by phentolamine and from -5.6 ± 3.0 to -3.5 ± 2.5 by indomethacin, P <0.01). Hexamethonium, propranolol and L-NNA (inhibitor of NO synthetase) did not affect the action of progesterone (P> 0.05). CONCLUSION: The study suggested that progesterone can inhibit the contractile activity of isolated gastric strips in rats and the mechanism seems to be a direct one except that the action on gastric body is mediated through prostaglandin and adrenergic α receptor partly.