Acute oral toxicity of inorganic cobalt compounds in rats

Eight cobalt compounds were administered to rats by gastric intubation, and the following LD50 values (in mg anhydrous compound/kg body weight) were determined: cobalt(II) fluoride 150, cobalt(II) oxide 202, cobalt(II) phosphate 387, cobalt(II) bromide 406, cobalt(II) chloride 418, cobalt(II) sulphate 424, cobalt(II) nitrate 434 and cobalt(II) acetate 503. After administration of the cobalt compounds, body temperatures decreased by 2.5-7.5 degrees C. The liver, heart and kidneys of rats given cobalt(II) fluoride or oxide were examined microscopically. Hyperaemia, haemorrhage and cytoplasmic changes were noted, while the kidney glomeruli were very rich in cells and basal membranes were thickened. Cells of the proximal tubules were swollen and showed vacuolization and degeneration. In the hearts of some rats proliferative and oedematous interstitial tissue and swollen muscle fibres were observed, and focal degeneration, vacuolization and necrosis associated with disappearance of the cross striations were also noted.