Accumulation and influence of mercury released from dental amalgam in living body

这项研究是为了获得有关汞在活体中从牙科银汞合金中释放的累积和影响的信息。为了达到这个目的，我们采用了一种实验动物模型，在该模型中，怀孕的大鼠接受了银汞合金充填。我们测量了母亲和胎儿器官和血液样本中的总汞。本研究的主要结果如下：实验1.银汞合金修复体修复后，汞合金在母体和胎儿器官中出现。在母亲中，实验组的大脑、肝脏、肾脏和胎盘的汞浓度明显高于对照组，其中肾脏的汞浓度最高，其次是胎盘、肝脏和大脑。在胎儿中，实验组的脑、肝脏汞浓度显著高于对照组。胎儿器官中汞含量最高的是…实验2.随着银汞合金充填量的增加，母体和胎儿脏器中汞的浓度呈上升趋势，胎儿体重呈下降趋势.实验3.为观察银汞充填体对胎儿生长发育的影响，用玻璃离子水门汀代替银汞充填体对4颗牙齿进行了充填.在母亲中，实验动物的生长曲线低于对照动物。妊娠早期饮食和水的摄入量明显低于对照组。两组间差异无统计学意义，但胎儿体重均低于对照组。这些结果表明，牙科治疗本身似乎影响了怀孕早期大鼠饮食和水的摄入量，并减缓了母鼠和仔鼠的生长发育。本研究的这些结果和实验2的结果表明，银汞合金充填本身可能不会影响胎儿的生长。实验4.本研究旨在探讨孕鼠汞合金充填与第二代和第三代后代器官中汞浓度的关系。第2代实验动物的脑、肝、肾、脾中汞含量高于对照组，但差异不显著。在第三代，汞浓度在实验组和对照组之间几乎相同。实验5本实验是为了研究汞在母鼠和仔鼠器官中积累的化学形态。在母亲中，实验动物的全血、红细胞和血浆汞含量显著高于对照组。在胎儿中，实验动物全血汞含量显著高于对照组。实验动物的母胎比、红细胞/血浆比均低于对照组。另一方面，实验组的PF比率高于对照组。元素汞被引入胎儿后的化学转化尚不清楚，尽管有人认为元素汞经历了与母体动物相似的氧化过程。红细胞和血浆中汞浓度的比率取决于汞化合物的化学形式；汞暴露在汞蒸气中后，红细胞中的汞比血浆中的汞多，但无机汞暴露后，情况正好相反。在本实验中，实验组母亲的红细胞/血浆比值明显低于对照组。这表明血液中存在的化学形式可能是无机的。在胎儿器官中，血液从胎盘通过脐静脉返回，通过静脉导管进入胎儿循环，主要通过肝脏。此外，众所周知，过氧化氢酶有很大的能力将汞蒸气氧化成离子汞，这种酶在肝脏中含量丰富。通过胎盘屏障的汞的化学形态可能是元素的。虽然我们无法检测胎儿血样中红细胞和血浆中汞的浓度比，但胎儿循环系统中的汞可能是无机的，因为汞在肝脏中的积累量最高。因此，最有可能的是，通过胎盘的牙科银汞合金填充物释放出的部分汞在胎儿肝脏中被氧化为离子汞，并在该器官中积累。较少

This study was carried out to obtain information regarding the accumulation and influence of mercury released from dental amalgam in a livin body. To address this object we have employed an experimental animal model in which pregant rat received amalgam tooth fillings. We measured a total mercury in organs and blood samples of mother and their fetus. The results obatined in this study were summarized as follows.Experiment 1.Mercury from dental amalgam appeared in maternal and fetal organs after amalgam tooth restorations in the mother rtas. In mothers, the mercury concentrations of the brains, livers, kidneys and placentas from the experimental group were significantly higher than those of the controls, and the highest mercury was found in the kidneys, followed by placenta, liver and brain. In fetuses, the mercury concentrations of the brain, liver from the experimental group were significantly higher than those of the controls. The highest mercury concentration among fetal organs was … More found in liver, followed by kidneys and brain.Experiment 2.With the increasing number of amalgam fillings, mercury concentrations in organs of mother and their fetuses tended to increase, while body weight of fetus tended to decrease.Experiment 3.In order to examine the influence of amalgam fillings on growth of fetuses, 4 teeth were fillied with the glass ionomer cement instead of amalgam. In mothers, growth curves of the experimental animals was lower than that of the control animals. Intake of the diet and water were significantly lower than those of the controls at the early pregnant stage. Althogh, significant difference was not observed, body weight of the fetus was lower than that of the controls. These results indicated that dental treatment itself seemed to influence the intake of the diet and water at the early pregnant stage and to slow the growth of mother rats and their fetuses. These findings of this study and the results of the experiment 2 suggested that it was likely that amalgam fillings themselves did not influence the growth of fetuses.Experiment 4.This study was carried out to examine the relation between amalgam fillings in pregnant rats and marcury concentrations in organs of offspring's of second and third generations. The mercury contents in the brain, liver, kidney and spleen of the experimental animals of the second generation were higher than those of the controls, although significant differences were not observed. In the third generation, mercury concentrations were almost the same between experimental and control groups.Experiment 5.This expriment was carried out to examine the chemical form of mercury accumulated in organs of mother rats and their fetuses. In mothers, the mercury contents in the whole blood, erythrocyte and plasma of the experimental animals were significantly higher than those of the controls. In fetuses, the mercury contents in the whole blood of the experimental animals were significantly higher than that of the controls. Fetus to mother ratio, and Erythrocyte and plasma ratio of the experimental animals were lower than those of the controls. On the other hand, PF ratio of the experimental group was higher than that of the control group. Chemical transformation of elemental mercury after introduction into fetuses remains unclear, though it is suggested that elemental mercury undergoes an oxidation process similar to that occurring in maternal animals. Ratios of mercury concentrations in erythrocytes and plasma depend upon the chemical forms of mercury compounds ; after mercury exposure to mercury vapor, more mercury is found in red cells than in the plasma, but after inorganic mercury exposure, the reverse is true. In this experiment, the erythrocyte to plasma ratio of mothers of the experimental group was significantly lower than that of the control group. This indicates that the chemical form existing in the blood stream is possibly inorganic. In the fetal organs, blood returning from the placenta through the umbilical veins enters fetal circulation through the ductus venosus, mainly by passing through the liver. Furthermore, it is known that catalase has a great capacity to oxidized mercury vapor into ionic mercury and that this enzyme is contained abundantly in liver. The chemical form of mercury passing through the placental barrier is possibly elemental. Although we could not examined the mercury concentration ratio of erythrocytes and plasma in the blood sample of the fetus, mercury in the fetal circulation system is possibly inorganic because the highest mercury accumulation was found in the liver. Consequently, it is most likely that part of the mercury released from the dental amalgam filling passing the placenta is oxidized into ionic mercury in fetal liver and accumulates in that organ. Less