The measurement of the survival of human erythrocytes by in vivo tagging with Cr51.

T HE I)ETEItMINATION of the average survival tinse or life spats of erythrocytes etshatices nsarkedly the appraisal of the etiology of atsensias amsd other pathologic states.’ The most direct approach is to measure the survival of the erythrocytes svithits their tiattsral envirotstssetit. Heretofore, techtsics pertssittitsg this approach have itsvolved the use of isotopes of irots (Fe59), isitrogets (N’5) atid carbots (C’4) atsd have beets cumbersonse due to the complexities of the analysis of these isotopes atsd the factor of reutilizat.iots of the isotope by erythro( y 5 The differential agglutination techtsic of Ashhy, although very useful, permits otsly the appraisal of dotsor cells withits a secotsd individual. Ats in vitro nsethod has beets developed for t.aggitsg a randons populat.iots of eryt.hrocyt.es with radioactive chronsiuni (Xa Cr51O4) atsd measuritsg their its vivo survival followitsg the autoor homotratssfusiots of the tagged cells.24 ‘[isder these (otsditiolss a plot of the erythrocyte decay rate as tsseasured by the deerensemit of radioactivity is curvilitsear its the normal state. This represents a depart.ure from the expected reet.ilitsear function which is ats expression of destructiots of cells (otitrolled by otsly a sitsgle factor, a cotsstatst determinatst cell life spats. This deviatiots frotss the rectilitsear futsct.iots has beets cotssidered to he due to either a random “leak” of chronsium from intact cells3 or a ratsdon’i cell death froni utsktiowts factors possibly related to the process of in vitro tagging.4 The mssechatsical atsd physical trauma of the its vitro taggitsg procedure can be obviated by taggitsg the red cells itt vivo. Erythrocytes have beets tagged in vivo by the intravenous injectiots of 200-300 tssicrocuries of Xa Cr51O4. The procedures atsd results of this approach are givets below.