Oxidative stress status and development of late organogenesis stage rat whole embryos cultured from gestational days 13.5 to 14.5.

A new method for culturing rodent whole embryos at the late organogenesis stage was developed using a roller-bottle system with intermittent gassing. Rat embryos were cultured for 24 h from gestational day (GD) 13.5 to 14.5. Growth and metabolic comparisons were made between in vivo embryos and embryos of the same GD cultured under various media and conditions. Crown-rump length, head length and protein content were used as growth indicators. Biologic markers such as embryonic tissue concentration of glutathione (GSH), glutathione disulfide (GSSG) and lipid peroxidation were used as assessments of metabolic activity in terms of oxidative stress. Embryos cultured with media consisting of either 15% or 20% male rat serum and balanced with Dulbecco's Modified Eagle Medium (DMEM) were found to most closely match in vivo embryos. 6 h gassing intervals and 5 mL medium volume/embryo provided optimal conditions for cultured embryos. By shortening the 24 h embryo culture period to 12 h, embryonic haemorrhaging was avoided. Moreover, the 12-h cultured embryos showed similar redox GSH/GSSG ratios and similar GSH content to the in vivo embryos, which was not observed in the embryos cultured under 24 h culture conditions. The present work demonstrates the utility of late organogenesis stage embryo culture as a model for the assessment of in vivo embryonic growth and oxidative stress indices.

Effects of prenatal methylmercury exposure on brain monoamine oxidase activity and neurobehaviour of rats.

Monoamine oxidase (MAO) regulates levels of dopamine, serotonin, and noradrenaline in the nervous tissue and is required for proper neuronal development. The purpose of this study was to determine if oral exposure of adult female rats to methylmercury (MeHg) at 0.5 or 1 mg/kg/day before and during pregnancy would affect MAO activity in various brain regions of the offspring. Offspring neurobehaviour performance was also assessed. The brain MAO activity of female offspring was reduced at both MeHg doses with significantly lower values noted in the brainstem region. No significant MeHg dose effects on MAO activity were observed in the male offspring. Neurobehavioural evaluations indicated that MeHg exposure altered auditory startle in the female offspring. Rat whole embryos (gestational day 13.5) cultured with 750 microg/L MeHg in vitro significantly decreased total MAO activity by 15%. In conclusion, this study demonstrated that exposure to MeHg in rats before and/or during gestation resulted in a reduction of MAO activity in the developing embryo and brainstem of the female offspring with accompanying changes in auditory startle response. Evaluation of MAO activity may serve as an indicator for neurotoxicity following developmental exposure to MeHg and should be further investigated.