title: Turnover in humans of iodine- and cobalamin-labeled transcobalamin I and of iodine-labeled albumin.
abstract: Purified transcobalamin I labeled with radioactive iodine and cobalamin was used for turnover studies in 17 humans. Mean fractional catabolic rate was 0.15 d-1 and mean distribution ratio was 0.57. No difference was observed between the turnover in a control group and in patients with vitiligo or pernicious anemia. The plasma curves of the iodine and the cobalamin label were identical, indicating that cobalamin was liberated from transcobalamin I only when this protein was degraded. It was further concluded that transcobalamin I was of minor importance for the transport of cobalamin from the gut to the tissues. The turnover of transcobalamin I was correlated to the turnover of albumin in 9 patients studied with both proteins.
mesh_terms: D000328:Adult; D000368:Aged; D000752:Anemia, Pernicious / Q000097:blood; D001798:Blood Proteins / Q000378:metabolism*; D002986:Clinical Trials as Topic; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D010953:Plasma Volume; D011485:Protein Binding; D012711:Serum Albumin, Radio-Iodinated / Q000378:metabolism*; D014155:Transcobalamins / Q000378:metabolism*; D014805:Vitamin B 12 / Q000097:blood; D014820:Vitiligo / Q000097:blood
chemical_list: D001798:Blood Proteins; D007457:Iodine Radioisotopes; D012711:Serum Albumin, Radio-Iodinated; D014155:Transcobalamins; D014805:Vitamin B 12