Morimoto T, Sekizawa A, Hirose K, Suzuki A, Saito H, Yanaihara T
Department of Obstetrics and Gynecology, Showa University, Tokyo, Japan.
Endocr J. 1993 Apr;40(2):179-83. doi: 10.1507/endocrj.40.179.
Biochemical investigations have shown the presence of the enzyme phenylethanolamine N-methyltransferase (PNMT), which converts norepinephrine (NE) to epinephrine (E) in human pregnant tissues, e.g. myometrium and fetal membranes. The enzymatic activity of PNMT in myometrium is known to decrease during labor. In the present study, PNMT activity in chorio-decidua was measured and the effect of labor and prostaglandins (PG) on PNMT activity was determined. A cytosol fraction of chorio-decidua was incubated with [14C]-S-adenosyl-L-methionine and normetanephrine for 60 min to measure PNMT activity. Fetal membranes were obtained at elective Cesarean section and normal vaginal delivery from full term pregnant women, and the activity of PNMT in chorio-decidua was compared. Significantly lower activity in chorio-decidua obtained from normal vaginal delivery than that from elective Cesarean section was observed. The concentration of 13, 14-dihydro-15-keto-prostaglandin F2 alpha (DHK-PGF2 alpha) in amniotic fluid obtained at normal vaginal delivery were measured by RIA, and the relationship of the DHK-PGF2 alpha level to PNMT activity was studied. There was a significantly negative correlation between the concentration of DHK-PGF2 alpha in amniotic fluid and PNMT activity in chorio-decidua. When various concentrations of PGF2 alpha were pre-incubated with mined chorio-decidua for 2 h, PNMT activity was decreased in a dose dependent manner. These results indicated that PGF2 alpha might affect the bioconversion of NE to E in fetal membranes. The presence of this enzyme in fetal membranes may play an important role in regulating the concentration of catecholamines during pregnancy and parturition.
生化研究表明，在人类妊娠组织（如子宫肌层和胎膜）中存在苯乙醇胺N-甲基转移酶（PNMT），该酶可将去甲肾上腺素（NE）转化为肾上腺素（E）。已知子宫肌层中PNMT的酶活性在分娩过程中会降低。在本研究中，测量了绒毛蜕膜中PNMT的活性，并确定了分娩和前列腺素（PG）对PNMT活性的影响。将绒毛蜕膜的胞质溶胶部分与[14C]-S-腺苷-L-甲硫氨酸和去甲变肾上腺素一起孵育60分钟，以测量PNMT活性。从足月孕妇的择期剖宫产和正常阴道分娩中获取胎膜，并比较绒毛蜕膜中PNMT的活性。观察到正常阴道分娩获得的绒毛蜕膜中的活性明显低于择期剖宫产获得的活性。通过放射免疫分析测量正常阴道分娩时获得的羊水中13,14-二氢-15-酮-前列腺素F2α（DHK-PGF2α）的浓度，并研究DHK-PGF2α水平与PNMT活性的关系。羊水中DHK-PGF2α的浓度与绒毛蜕膜中PNMT的活性之间存在显著的负相关。当将不同浓度的PGF2α与提取的绒毛蜕膜预孵育2小时时，PNMT活性呈剂量依赖性降低。这些结果表明，PGF2α可能会影响胎膜中NE向E的生物转化。胎膜中这种酶的存在可能在调节妊娠和分娩期间儿茶酚胺的浓度方面发挥重要作用。
