Erythroid "bursts" in semi-solid agar diffusion chambers: effect of cyclophosphamide administration to host and of hydroxyurea to donor animals.

Growth of erythroid bursts was induced in peritoneal diffusion chambers in a semi-solid agar medium. Mice of the "Sabra" strain received single i.p. injections of cyclophosphamide (45 mg/kg) 24 h prior to implantation of chambers. Rats of the Hebrew University strain, used as donors, received single i.p. injections of hydroxyurea (400 mg/kg), 9 h prior to being killed. Ten to fourteen days after chamber implantation, several erythroid colonies of ten to several hundred cells developed in the semi-solid agar medium. The erythroid cells in the colonies were benzidine-positive and at various stages of maturation. We suggest that growth of erythroid "bursts" in diffusion chambers, in hosts which had not received any specific erythropoietic stimuli, was made possible by a high concentration of BFU-E in the door marrow. The BFU-E enriched rat bone marrow resulted from administration of hydroxyurea which, after preferentially killing erythroblasts in cycle, stimulated mobilization of stem cells for the replenishment of the depleted compartment.