The vulnerability of the nervous system to toxic insult is particularly high during foetal life and early childhood. Exposures during this period, via maternal blood and/or milk, may result in neurobehavioural disorders, some of which may not become apparent before in adulthood. Methylmercury (MeHg) and polychlorinated biphenyls (PCB) are persistent environmental pollutants and may be present in some food products. Both are neurotoxic. It is suspected that MeHg and PCBs may act synergistically in inducing neurotoxic effects. Some data suggest that catecholaminergic systems, especially the dopaminergic one, are particularly vulnerable to the harmful action of MeHg and PCBs. This study aimed to assess the influence of separate or combined perinatal exposure to MeHg and PCB 153 on brain catecholamine contents in maturity. The subjects were adult (90-94 days of age) rats, progeny of mothers exposed to methylmercury (MeHg, CH₃HgCl) or 2,2’,4,4’,5,5’-hexachlorobiphenyl (PCB 153), or MeHg and PCB 153, from day 7 of gestation to day 21 post partum. MeHg was administered with drinking water at daily doses of 0.5 mg/kg b.w./day. PCB 153 was administered by gavage at daily doses of 5 mg/kg b.w./day. The concentrations of adrenaline (A), noradrenaline (NA), dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were determined by HPLC in homogenates of the following brain regions: olfactory bulb, hippocampus, striatum, occipito-temporal cortex, diencephalon, mesencephalon and cerebellum. The results suggest some exposure-related alterations in amine contents and point to the significant role of gender in their development. In the female MeHg-exposed progeny, the content of NA, DA and DOPAC in the mesencephalon was significanrtly elevated (by 43.1, 68.9 and 65.1%, respectively) while in the male progeny no differences were noted in any region of the brain. On the other hand, in the progeny exposed to PCB 153, some differences, i.e. increased NA concentration in the olfactory bulb (by 59.9%) and hippocampus (by 124.5%) and increased DA (by 75.0%) in the striatum were found in males, whereas in females significant differences were not found. In the case of combined exposure, the data suggest some effects in the female progeny only: a decreased concentration of A in the hippocampus (by 40.9%) but increased in the stratum (by 53.1%) and an increased DA concentration in the mesencephalon (by 78.9%). Summing up, the results confirm that gender may be an important determinant of the rat’s vulnerability to MeHg and PCB153. They provide no evidence, however, of a synergism in the action of these neurotoxicants when given perinatally on the brain catecholaminergic systems in adulthood. A rough analysis of the obtained data allows one to suspect an antagonistic rather than synergistic type of interaction.
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