Autoradiographic Evidence for Reutilization of DNA Catabolites by Granulocytopoiesis in the Rat

Abstract

The proliferating granulocyte precursor pool of rat bone marrow was labeled during DNA synthesis by continuous infusion and by single injection of 3H-thymidine (3H-TdR), as well as by single injection of 125I-iododeoxyuridine (125I-UdR). The appearance of neutrophilic granulocytes in the blood stream after these various labeling procedures was studied by autoradiography. Labeling patterns of blood neutrophils were identical during continuous infusion and after single injection of 3H-TdR, and 100% labeling of the blood compartment was achieved. Reutilization of DNA catabolites apparently occurs in granulocytopoiesis, leading to continuous availability of 3H-labeled DNA precursors even after a single injection of 3H-TdR. Attempts to suppress reutilization of label by infusion of cold thymidine 1 h after injection of 3H-TdR was unsuccessful. A change in the labeling pattern of blood neutrophils was seen after single injection of 125I-UdR, a DNA precursor poorly reutilized in comparison to 3H-TdR. This result provided further evidence for reutilization of DNA catabolites by the cell system investigated. Results indicate that TMP is the biochemical level of reutilizaton in granulocytopoiesis.