Growth of diffusion chamber hematopoietic colonies derived from spleen cells of rats administered hydroxyurea.

Donor rats of the Hebrew University strain were administered a single intraperitoneal injection of hydroxyurea (400 mg/kg body weight). 1--3 h following the administration of the drug, a suspension of spleen cells, the majority of which consisted of lymphocytes, was prepared. Spleen cells were placed in diffusion chambers and these were implanted in the peritoneal cavity of preirradiated mice. 5--8 days following implantation, erythroid and granulocytic colonies developed in 30.3% of the diffusion chambers studied. However, in most chambers, macrophages were observed. In control experiments with implantation of spleen cells of normal rats, granulocytic colonies did not grow and in only 3.1% of the chambers erythroid colonies were noted. Macrophage colonies, however, developed in all 32 control cultures. Our previous studies showed that administration of a single dose of hydroxyurea strips the rat bone marrow of approximately 50% of replicating cells within 9--10 h. The results of the present study indicate that such a severe depletion of rat marrow cells results in early committment of spleen stem cells to various blood cell lines.