Disposition, behavior, and toxicity of methylcyclopentadienyl manganese tricarbonyl in the mouse.

The disposition and toxicity of methylcyclopentadienyl manganese tricarbonyl (MMT), a potential substitute for lead in gasoline, was studied to investigate the different adverse effects in ddY mice after chronic oral administration at 0.5 g/kg in food for 12 months. There was no significant difference in intake between the control mice and the mice exposed to MMT (MMT group), but those given MMT suppressed weight significantly. The manganese content in the organs of the MMT group was 4.4-1.5 times significantly higher than that of the control group. In the MMT group, the manganese content was highest in the kidney, followed by the liver, thyroid gland, sublingual gland, and prostate gland. The blood manganese level in the MMT group was about 8 times higher than that in the control group. The urinary excretion of manganese in the MMT group was 5.4% of the daily oral intake. The organometallic form of the manganese involved is apparently absorbed more readily than inorganic forms. The stronger toxicity of MMT to the tissue than that of inorganic manganese is attributed to the significantly higher blood and tissue levels of manganese in the MMT group.