Oral Administration of Vitamin B12 Containing Cobalt60 to Rats

Recent reports by Chow and associates ( 1 , 3 ) have demonstrated that when vit. B12 is administered orally to rats or humans, no microbiologic activity appears in the urine. They concluded from these observations that oral administration results either in the conjugation of vit. B12 to a form unavailable for the microorganism, in poor absorption in the intestinal tract, or in conversion to a form incapable of being excreted by the kidneys. Later they observed (unpublished work) that stool samples from rats receiving vit. B12 by mouth contained considerably more of this vitamin than stools excreted before administration. Although these data might be taken to indicate poor utilization of vit. B12, this interpretation is complicated by the presence of some vit. B12 in the feces of untreated, normal rats and by the unreliability of the microbiologic assay for this vitamin in stool. The availability of radioactive vit. B12 containing cobalt60 reported by Chaiet, Rosenblum and Woodbury( 2 ) simplifies the analytical problem and permits a differentiation between the administered vitamin from that originally present, granting that the radioactivity due to cobalt60 found in the animal represents administered vit. B12. It is therefore of interest to ascertain the distribution of vit. B12 as manifested by the presence of t radioactive cobalt60 reported by Chaiet, Rosenblum and Woodbury( 2 ) simplifies the analytical problem and permits a differentiation between the administered vitamin from that originally present, granting that the radioactivity due to cobalt60 found in the animal represents administered vit. B12. It is therefore of interest to ascertain the distribution of vit. B12 as manifested by the presence of t radioactive cobalt60 in urine and stool, as well as in certain organs of rats following oral administration. The results of such a study are reported below. Experimental. Four normal rats weighing between 250 and 300 g were put into metabolism cages and fed a soy bean diet( 3 ). Collections of urine and stool were made for 2 5 consecutive days. On the third day, 0.89 mg of radioactive B12,∗ with a specific activity 1 of = 0.2 microcurie per milligram, was administered orally to each rat. Daily collections of urine and fecal matter were again made for 3 to 4 consecutive days.