Localization of a Lactic Dehydrogenase Isozyme in Nuclei of Young Cells in the Erythrocyte Series. ∗

Summary

1. The mature erythrocyte is the only human cell thus far studied which lacks LDH isozyme 5, not observed in hemolysates from 500 individuals. Hemolysates from 5 patients with anemia and reticulocytosis exhibited isozyme 5. Hemolysate from an anemic patient without reticulocytosis did not contain isozyme 5. 2. Hemolysates from 3 normal guinea pigs lacked isozyme 5. After anemia induced by phenylhydrazine administration and during the period of reticulocytosis LDH isozyme 5 appeared in the guinea pig hemolysates. 3. A preparation enriched in young cells of the erythrocyte series revealed more LDH isozyme 5 than did hemolysate prepared from the untreated erythrocytes of the same blood. 4. Nuclei prepared from duck and chicken erythrocytes exhibited the majority of LDH activity in a single cathodal band in contrast to the isozyme pattern of the supernatant material. 5. In conclusion, LDH isozyme 5, absent in the anucleated mature erythrocytes of man and guinea pig, is present in the earlier forms of the erythrocyte series which are nucleated or contain primary nuclear products. In addition to those isozymic alterations previously described during embryonic development, isozymic changes also occur in the adult animal during the processes of cell aging.