Differences in liver weight, mortality in cerium-treated mice and 144Ce levels in blood, liver, urine and faeces at various intervals after treatment with nafenopin and pregnenolone 16-alpha-carbonitrile (PCN).

Pretreatment with nafenopin and pregnenolone-16-alpha-carbonitrile (PCN) decreased the acute lethal toxicity in mice induced by cerium chloride (12 mg/kg resp. 15 mg/kg). Treatment with nafenopin and PCN increased the relative liver weight. More cerium accumulated in the liver of nafenopin- and PCN-treated animals than in controls during the first hours after injection. After 14 days the amount of cerium in the livers of nafenopin-treated animals was significantly higher. The concentration of cerium as a percentage of the injected dose calculated per mg liver was lower during the first day in the nafenopin group and higher in the PCN group than in the control group. After 6 days cerium concentration decreased significantly less in the livers of the nafenopin group. Cerium concentration in the blood was significantly lower in the nafenopin group during the first day. Only small amounts of the injected cerium were excreted in the urine, and no difference between treated and untreated animals was found. The amount of cerium excreted in faeces was somewhat smaller in the nafenopin-treated animals during the whole experiment.