Tissue Cobalt Content and Excretion in Mice and Rats Following Injection of Cobalt Chloride

Tissue content and excretion of cobalt was investigated in mice and rats following the injection of various doses of cobalt chloride.1. To determine the injection dose, female mice were injected subcutaneously and male mice intraperitoneally with cobalt chloride, and LD50 of 40.8mg/kg in female and 36.7mg/kg in male mice were obtained.2. Male and female mice were injected subcutaneously with 5, 10 and 20mg/kg, each equivalent to 1/8, 1/4; and 1/2; of LD50, of cobalt chloride six days a week for 64 days.Body weight increased only in male mice injected with a dose of 5mg/kg in comparison with control group. Polycythemia was observed only in female mice treated with various amount of cobalt chloride. The relative wet weight of the heart, lungs and liver incresed, while the relative dry weight of these organs decreased, which suggest that cobalt acted to increase the water content of these organs. The testes, however, decreased markedly in relative wet weight, which may indicate the presence of damage in testes following cobalt treatment.The amount of cobalt accumulated in various organs in mice treated with 5 or 10mg/kg showed no significant increase proportional to the treatment period between groups treated for 15days and those for 64 days. The amount of accumulated cobalt in the liver and kidneys was not in proportion to the injected doses. A huge accumulated dose of cobalt in the liver and kidneys suggest that administered cobalt was transported by blood stream to the liver and excreted through the kidneys, while large amount of injected dose has been excreted rapidly.3. The urinary excretion and fecal output of cobalt was investigated for 7 days in rat treated with a single injection of 40mg/kg. The cobalt content of treated animals was highest in the liver followed by the kidneys, heart, spleen and lungs, while in normal control rats the order was liver, spleen, kidneys, lungs and heart. A remarkable high content was noted in the heart of cobalt-treated rats. The injected cobalt was excreted mainly in the urine: approximately 22% was excreted during 24 hours after injection, and 45% was excreted during the first week, while fecal output was only 15% during the first week. Accordingly 60% of the injected dose was excreted during the first week.A single cobalt injection caused a marked decrease of the copper content of the liver, kidneys and spleen, and there was an associated increase in the urinary excretion of copper. These findings suggest that cobalt and copper may replace each other in these organs and that cobalt may affect copper metabolism in the animal.