Study on melatonin in human and rat placental tissue

Summary Human and rat placental tissues contain high levels of melatonin even during daytime. The alteration of placental melatonin suggests that the role of melatonin in the placenta differs from that in the pineal gland. Expression of the gene encoding AA-NAT strongly suggests that placental melatonin was synthesized in the placenta. However, the precise mechanism by which placental melatonin is regulated remains to be elucidated.