Effects of hydroxyurea pretreatment of donor rats on growth of haematopoietic diffusion chamber colonies in mice.

A single dose of hydroxyurea (HU) (400 mg/kg body weight) was injected i.p. into rats. Hydroxyurea, a potent DNA synthesis inhibitor, killed bone marrow cells in the S-phase of the cell cycle. 9-10 h after HU administration, the rat bone marrow contained large numbers of necrotic cells and appeared predominantly lymphoid. Within 24-48 h of HU injection, resumption of normal haematopoiesis was observed. Rat bone marrow, 9-10 h following HU administration, was implanted in peritoneal diffusion chambers (DC) in irradiated mice. The results obtained suggest that pretreatment of donor rats with HU increases the bone marrow content of progenitor cells. The stem cell-enriched marrow was conductive to enhanced growth of DC colonies in irradiated mice.