Studies on Poisonous Metals. X. Metabolic Fate of Manganese after Oral Administration of Excessive Manganese Chloride in Rats

The metabolic fate of manganese after the oral administration of excessive manganese chloride in rats was studied. After a single oral administration of manganese chloride (100 mg Mn/kg), the manganese levels in most tissues temporarily increased and then rapidly decreased to the control values within 24-48 h ; however, the manganese levels in the pancreas, brain, and bone were considerably higher than the control values even at 48 h after the administration. The tissue levels of manganese in rats given a single oral administration of 200 or 400mg Mn/kg were markedly higher than those after 100mg/kg and remained much higher than the control and 100 mg Mn/kg values at 24 h after the administration. The increase in the tissue retention of manganese at such high doses was found to be due to a decrease in the biliary excretion of manganese, which is the major excretion route of the metal. On the other hand, when manganese (100mg Mn/kg) was given every other day for three months, little tissue accumulation of manganese was observed in rats.