Submitted to: Biological Trace Element Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/1997
Publication Date: N/A
Interpretive Summary: Manganese is a trace element essential for human health. However, exposure to excessive amounts of manganese has been shown to be toxic; principally to brain. Various brain disorders have been reported in humans receiving all of their nutrients intravenously, and these abnormalities have been attributed to manganese intoxication because of elevated serum manganese. Because manganese is excreted mainly by the liver via bile, anything that decreases biliary excretion of manganese may increase accumulation of manganese in the brain. We prevented rats from excreting manganese by surgically tying off (ligating) their bile ducts to determine whether this would affect the accumulation of radioactive manganese in the brain. In contrast to our expected results, the ligated animals had less radiomanganese in brain than did sham operated animals.
Technical Abstract: Neurologic and radiologic disorders have been reported to occur in miners inhaling manganese-laden dust and in humans receiving long-term parental nutrition. These abnormalities have been attributed to manganese intoxication because of elevated serum manganese concentrations. Because the liver, by way of the bile, is the major route of manganese excretion, it is possible that anything that decreases biliary excretion could increase accumulation of manganese in the brain. The purpose of this study was to determine whether biliary ligation would increase manganese accumulation in the brain of rats that were exposed to deficient or adequate amounts of dietary manganese. The first experiment had a 2 x 3 factorial design, 2 levels of manganese (0 or 45 ug/g diet) and three surgical treatments (control, sham or bile-ligation). Animals were sacrificed 10 days after being fed 54**Mn. In experiment 2, animals that had a sham operation or bile-ligation were sacrificed at 8 time points after being injected intraportally with 54**Mn complexed to albumin. The biliary ligated animals had a significantly (p<0.00l) smaller percentage of the 54**Mn in their brains than the sham operated animals. Manganese deficiency had a similar effect. However, we did observe an increased accumulation of the radioisotope in the brain over time, which suggests that animals may need to have their bile duct ligated for a much longer period of time before increased accumulation of 54**Mn would be observed in their brains.