Alleviation of maternal hyperthermia-induced early embryonic death by administration of melatonin to mice

: Maternal hyperthermia induces early embryonic death via increased oxidative stress to the embryo. In this study, we examined whether melatonin administered to heat‐stressed pregnant mice would reduce hyperthermia‐induced embryonic death. Mice were heat stressed (12 hr at 35°C, 60% relative humidity) on the day of mating and melatonin (3 mg/kg body weight) was injected subcutaneously every 2 hr during heat exposure. Thereafter, zygotes were collected, and in vitro developmental ability and intracellular glutathione (GSH) content were assessed. In addition, reactive oxygen species (ROS) levels and free radical scavenging activity (FRSA) in the oviduct as well as lipid peroxidation in the liver were measured. Melatonin administration was associated with a tendency for higher intracellular GSH content in zygotes (1.67 pmol/zygote) and a significantly higher percentage of embryos that developed to the morula or blastocyst stage (47.91%; P