Differential Excretion of Cobalt-containing Products Following Administration of Co60-labelled Vit. B12, to Rats

Abstract

The excretion pattern of radioactive substance following parenteral administration of 0.25 ug of cobalt60-labeled vitamin B12 to the young rat was studied. Urinary excretion of radioactivity reached a maximum during the first 8 hours after labeled vitamin B12 administration, then rapidly declined; fecal excretion rose progressively through the 3d day. Moreover, administration of a large dose of unlabeled vitamin B12 subsequent to radioactive B12 significantly increased urinary but not fecal excretion of radioactivity. From this differential excretion pattern, it was inferred that labeled vitamin is altered prior to its excretion into the intestinal tract. The fecal route was shown to be the major excretory pathway for radioactivity resultant from parenteral introduction of Co60 vitamin B12; after the first 8 hours, the ratio of radioactivity excreted for a 10-day period via fecal and urinary pathways was 7:1, respectively. Sex did not appear to influence excretion of Co60-tagged products. Similarly, administration of large quantities of testosterone propionate to either females or males did not alter the excretion pattern.