Tamura Hiroshi, Takayama Hisako, Nakamura Yasuhiko, Reiter Russel J, Sugino Norihiro
Department of Obstetrics and Gynecology, Yamaguchi University Graduate School of Medicine, Ube, Japan.
J Pineal Res. 2008 Apr;44(3):335-40. doi: 10.1111/j.1600-079X.2007.00537.x.
We investigated how maternal melatonin is regulated in pregnant rats. To examine the involvement of the conceptus (fetus and placenta) in serum melatonin concentrations, the number of conceptuses was experimentally reduced to one on day 7 of pregnancy (1-conceptus group). Maternal circulating nighttime melatonin levels increased toward day 21 of pregnancy and rapidly decreased to the non-pregnancy levels after parturition, whereas the maternal serum nighttime melatonin levels of the 1-conceptus group on day 21 of pregnancy were significantly lower than normal pregnancy bearing dams more than 10 conceptuses. When the fetuses were removed by fetectomy (all fetuses but not the placentae) on day 12 of pregnancy, serum melatonin concentrations were not decreased. To examine the source of circulating maternal melatonin, mRNA expression of N-acetyltransferase (NAT), which is a late limiting enzyme for melatonin synthesis, was examined in the placenta and fetal pineal. NAT was not expressed in the placenta and was negligible in the pineal gland of the fetus compared with the mother's pineal gland. To examine the effect of placental hormones on maternal melatonin production, a conditioned medium, which was made by incubating placenta of day 20 of pregnancy with medium, was injected into the 1-conceptus dams from day 17 to day 20 of pregnancy. Injection of conditioned medium significantly increased serum melatonin concentrations compared with the control values whereas charcoal treatment abolished the stimulatory effect of conditioned medium. In conclusion, maternal circulating melatonin is from the maternal pineal gland and is increased by placental hormones during pregnancy.
我们研究了孕鼠母体褪黑素是如何被调节的。为了检测孕体（胎儿和胎盘）对血清褪黑素浓度的影响，在妊娠第7天通过实验将孕体数量减少至1个（单孕体组）。母体夜间循环褪黑素水平在妊娠第21天逐渐升高，分娩后迅速降至非妊娠水平，而妊娠第21天单孕体组的母体血清夜间褪黑素水平显著低于怀有10个以上孕体的正常妊娠母鼠。在妊娠第12天通过胚胎切除术（去除所有胎儿但保留胎盘）去除胎儿后，血清褪黑素浓度并未降低。为了检测母体循环褪黑素的来源，检测了褪黑素合成的晚期限速酶N - 乙酰转移酶（NAT）在胎盘和胎儿松果体中的mRNA表达。NAT在胎盘中未表达，与母体松果体相比，在胎儿松果体中的表达可忽略不计。为了检测胎盘激素对母体褪黑素产生的影响，将妊娠第20天的胎盘与培养基孵育制成的条件培养基，在妊娠第17天至第20天注射到单孕体母鼠体内。与对照值相比，注射条件培养基显著提高了血清褪黑素浓度，而活性炭处理消除了条件培养基的刺激作用。总之，母体循环褪黑素来自母体松果体，在妊娠期间会因胎盘激素而增加。
