Kinetics of Plasma Hemoglobin Catabolism in the Rat. II. Cr 51 -Tagged Hemoglobin. ∗

Summary

(1) Following in vitro labeling of erythrocytes with Na₂Cr⁵¹O₄, a considerable amount of the Cr⁵¹ was found unattached to hemoglobin. (2) This unattached Cr⁵¹ lost the ability to label erythrocytes, and when given intravenously, was excreted rapidly by the kidneys. (3) Hemoglobin-bound Cr⁵¹ was cleared from the blood the same as was previously reported with I¹³¹-hemoglobin. After clearance, however, much tissue retention of Cr⁵¹ was noted. (4) Rats metabolized homologous and canine hemoglobin similarly, with slow excretion of Cr⁵¹ by the kidneys. (5) The clinical implications of these findings indicating some peculiar metabolic characteristic of Cr⁵¹-tagged erythrocytes are discussed.