Objective To explore the potential effects of continuous aluminum exposure from maternal pregnancy and lactation period to offspring adulthood on spatial learning and memory, and miR-132 expression in hippocampus of offspring rats.
Methods Twelve pregnant SD rats were randomly divided into three groups receiving AlCl3 exposure via drinking water at 0, 600, and 1 000 mg/L (control group, low aluminum group, and high aluminum group), respectively. The pregnant rats were treated from pregnant day 0 to postnatal day (PND) 21 of the offspring rats. From PND22 to PND90 (adulthood), eight offspring rats (four males and four females) from each group were treated with the same protocol as the mother rats. The offspring rats were weighed every two weeks, tested in Morris Water Maze, and caged to collect 24-hour urine samples before euthanasia. Then hippocampus samples were collected from the euthanized rats to observe the pathological changes by HE staining. The levels of aluminum in urine and brain were detected by graphite furnance atomic absorption spectrometry. MiR-132 expression levels in hippocampus were measured by real-time PCR.
Results Compared with the control group, the body weights of offspring 0-12 weeks after birth in the high aluminum group were decreased (Ps < 0.01). In the Morris Water Maze test, on the third day and fourth day the escape latency in the exposure groups were increased (Ps < 0.01), the time of first arriving platform increased and the number of passing platform decreased in the high aluminum group compared with the control group (P < 0.05, P < 0.01). The levels of aluminum in urine in the two exposure groups were (11.84±1.03) μg/L and (16.32±1.32) μg/L, and the levels in brain were (12.69±0.43) μg/g and (16.61±0.93) μg/g, all higher than those in the control group (Ps < 0.01). Compared with the control group, the exposure groups showed decreased hippocampus neurons with nuclear pyknosis, hyperchromatic nucleus, and deformation of cells. MiR-132 expression levels in the two exposure groups were 1.48±0.35 and 1.62±0.38, respectively, much higher than that in the control group (1.00±0.12) (P < 0.05, P < 0.01).
Conclusion Continuous exposure to aluminum could impair spatial learning and memory ability of offspring rats, and increased expression of miR-132 in hippocampus may be associated with this phenomenon.
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