title: Enhancement by L-methionine of contractile responses to acetylcholine and high KCl in uterine segment.
abstract: The contractile responses of isolated uterine segments from 17 beta-estradiol-3-benzoate-treated ovariectomized rats to acetylcholine (ACh) and high KCl in Ca-depleted modified Locke-Ringer solution on addition of CaCl2 were used as indicators of Ca2+ influxes through ACh receptor- and voltage-operated Ca2+ channels, respectively. L-Methionine (L-Met) significantly enhanced these responses. The enhancement depended on the time of treatment with L-Met and concentration of L-Met. 3-Deazaadenosine (3-DAA) plus homocysteine thiolactone (HCTL), which inhibit S-adenosylmethionine-dependent methylation, caused dose-dependent inhibition of these contractile responses to ACh and high KCl. These inhibitory effects of 3-DAA plus HCTL were significantly attenuated in the presence of L-Met. Protein carboxylmethyltransferase and phospholipid methyltransferase activities were detected in the isolated uterine segment under conditions similar to those in which the contractile responses were observed. 3-DAA plus HCTL inhibited these enzyme activities. These findings suggest that S-adenosylmethionine-dependent methylations of protein and/or phospholipid in isolated uterine segment are involved in the contractile responses to ACh and high KCl in Ca-depleted modified Locke-Ringer solution on addition of CaCl2.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology; D005260:Female; D006710:Homocysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D008715:Methionine / Q000494:pharmacology*; D008780:Methyltransferases / Q000378:metabolism; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D010052:Ovariectomy; D050941:Phosphatidyl-N-Methylethanolamine N-Methyltransferase; D050918:Phosphatidylethanolamine N-Methyltransferase; D011189:Potassium Chloride / Q000494:pharmacology*; D011497:Protein O-Methyltransferase / Q000378:metabolism; D051381:Rats; D014372:Tubercidin / Q000494:pharmacology; D014590:Uterine Contraction / Q000187:drug effects*; D014599:Uterus / Q000201:enzymology
chemical_list: C018258:3-deazaadenosine; D006710:Homocysteine; D011189:Potassium Chloride; D008715:Methionine; C007957:homocysteine thiolactone; D008780:Methyltransferases; D011497:Protein O-Methyltransferase; D050918:Phosphatidylethanolamine N-Methyltransferase; D050941:Phosphatidyl-N-Methylethanolamine N-Methyltransferase; D014372:Tubercidin; D000109:Acetylcholine; D002118:Calcium