Effects Of Iron Supplementation During Pregnancy And Lactation On Iron Load, Nerve Reflex And Learning And Memory In Offspring

Objective To study the effects of overdose iron supplementation in rats during pregnancy and lactation on nervous reflex and ability of learning and memory of their offsprings.Methods In this study, a total of 30 pregnant rats were randomly divided into three groups, including the normal control group(NC), low-dose iron supplement group(LIS)(30 mg/kg·bw) and high-dose iron supplement group(HIS)(120 mg/kg·bw). NC received normal saline(2 ml), and the other two supplement groups were injected with different doses of iron dextran every other day during pregnancy and lactation. The body weights of the offsprings were weighted weekly for five weeks. Serum iron concentrations and the content of iron in brain in the 35-day offspring were determined by chromatometry. The activity of acetylcholinesterase(Ach E) and nitric oxide synthase(NOS) in brain in the 35-day offsprings were tested. Alterations of nervous reflex of the offsprings were observed at the 2nd day after birth through the negative geotaxis reflex, the avoidance precipice reflex and the surface righting reflex tests. Changes of learning and memory of the offsprings at the 28 th day after birth were detected during the successive 5 days by Morris water-maze.Results Serum iron concentrations in the offspring of HIS were significantly higher than NC(61.87 μmol/L vs 38.34 μmol/L, P<0.05) and LIS(61.87 μmol/L vs 38.45 μmol/L, P<0.05), but no significant differences were observed between NC and LIS(P>0.05). The content of iron in the brain of the 35-day offsprings of HIS was significantly higher than NC(3.28 μmol/gprot vs 1.84 μmol/gprot, P<0.05), but no significant differences were observed between LIS and NC(2.46 μmol/gprot vs 1.84 μmol/gprot, P>0.05).The body weights of the offsprings of HIS and LIS were significantly lower than NC(P<0.05). In the negative geotaxis reflex test, the positive occurring time of the offspring in HIS was markedly longer than NC(8.60 d vs 6.40 d, P<0.05) and LIS(8.60 d vs 5.40 d, P<0.05). Moreover, in the avoidance precipice reflex test, the positive occurring time of the offspring in HIS was significantly higher than NC(6.90 d vs 3.60 d, P<0.05) and LIS(6.90 d vs 3.30 d, P<0.05), respectively. However, there were no significant differences in the positive occurring time, negative geotaxis reflex and the avoidance precipice reflex tests between the offsprings of NC and LIS groups(P>0.05). Besides, in the surface righting reflex test, the positive occurring time of the offsprings in HIS was significantly higher than NC(6.10 d vs 3.90 d, P < 0.05) and LIS(6.10 d vs 2.70 d, P < 0.05), and LIS was higher than NC(P < 0.05). In addition, compared with NC(26.32 s), the average escape latency of offspring at the 2nd day was delayed in HIS(37.80 s)(P < 0.05). And the average escape latency at the 5th day of offsprings in HIS was significantly lengthened than NC(23.76 s vs 15.77 s, P < 0.05) and LIS(23.76 s vs 12.09 s, P < 0.05). The average swimming speed and the number of crossing platform were not significantly different among the groups(P>0.05). The Ach E activity in brain of the 35-day offsprings of HIS was significantly higher than the 35-day offsprings of NC(0.18 μmol/gprot vs 0.14 μmol/gprot, P<0.05), but the 35-day offsprings of NC and LIS were not significantly different(0.17μmol/gprot vs 0.14 μmol/gprot, P>0.05). The NOS activity in brain of the 35-day offsprings of HIS was significantly lower than the 35-day offsprings of NC(1.09 μmol/gprot vs 1.53 μmol/gprot, P<0.05), but the 35-day offsprings of NC and LIS were not significantly different(1.20 μmol/gprot vs 1.53 μmol/gprot, P>0.05).Conclusions Overdose iron supplementation in female rats during pregnancy and lactation increased the serum iron level and brain iron concentration of their offsprings. In the offsprings, injured nervous reflex function and impaired ability of learning and memory were observed. These injuries may be due to the increased brain iron concentrations, the increased acetylcholinesterase activity and the decreased nitric oxide synthase activity in the brain.