Effect of vitamin B12 on performance and tissue selenium content in rats fed sub-toxic levels of selenite.Toxicology. 1993 Dec 31; 85(2-3):101-15.T
The effects of vitamin B12 status on growth and tissue selenium distribution were studied in Sprague-Dawley rats chronically exposed to subtoxic levels of selenite. Vitamin B12 status was monitored by urinary methylmalonic acid excretion and by liver and plasma vitamin B12 levels. Selenite absorption was unaffected by dietary level of vitamin B12. A significant (P < 0.05) interaction of vitamin B12 and selenium was found on growth of rats fed vitamin B12 deficient or control diets. In vitamin B12 depleted rats, there were significant histologic changes in the liver that were characterized by micronodules and regeneration, bile duct reduplication, mild cirrhosis, necrosis of individual hepatocytes and other minor histologic changes. There was no gross or histologic evidence of liver toxicity in rats supplemented with vitamin B12. Rats pair-fed 9 mg/kg selenium with vitamin B12 had significantly lower liver and kidney selenium levels and significantly higher blood selenium levels compared to rats fed the diet without vitamin B12. These results are consistent with the hypothesis that vitamin B12 deficiency limits selenium methylation and excretion, resulting in higher tissue selenium levels and subsequent toxicity.