The effect of dimethylbenz(a) anthracene on murine hematopoiesis.

DMBA was given p.o. to young adult female CBA/J mice in two regimens, a single dose of 1 mg and 4 doses of 1 mg in weekly intervals. In the peripheral blood only a transient reticulocytopenia and thrombocytopenia was observed in both groups. After 4 doses the thymus and spleen weights were reduced up to 4 weeks after the last dose. In the bone marrow the cellularity was lower in treated animals than in controls. After 1 mg DMBA pluripotent stem cells (CFUc) in the marrow were reduced to about 50--70% over a 2- to 3-week period, in the spleen the CFUs concentration was reduced to 10% at day 3 with about normal levels after 3 to 4 weeks. The compartment of granulocytic committed stem cells (CFUs) in both organs followed the same pattern with an overshoot in CFUc concentration in the spleen after 3 to 4 weeks. After 4 doses CFUs and CFUc were more depressed, regeneration began about 2 weeks after the last dose in both organs. CFUc in the marrow had normal and in the spleen supra-normal concentrations 3 and 4 weeks after the last dose.