The plasma clearance and urinary excretion of parenterally administered 58Co B12.

LTERATIONS in the vitansin B12 concentrations of senuns amid umnimsc after the oral or pareisteral adnsitsistratiots of B12 can be followed by mssicrohiological niethods.’7 The imitroduct-iois of radioactive vitamssits B12 labeled with #{176}Co has also nsade it possible to study body distribution of the vitamssims after oral or paremsteral administration to amiinsabs amid humamus.8’3 Changes in the radioactivity of the plasma, however, have not beets studied. The purpose of this paper is to compare the changes its the plasmisa amid urinary comicemstrat-iomss of radioactive B12 its subje(ts with low, miormal arid elevated seruns B12 coticentratiomss, after snsall imitravemious imsjections (1.5 jig.) of radioactive vitamnin B12. After such imsjectiomis, the pbasnsa B12 comseemitrations us pat-iemsts wit-h B12 deficiemscy have beets measured niicrol)iologically amid also estinsated fnons the plasma radioactivity amid the results obtaimied by hot-h these methods (olsspared. These observatiotss have beets nsade with vitansims 1112 labeled wit-h short lived isotope #{176}Co.’4