Effect of benzene on fibroblastoid colony-forming units in mice.

After exposure of C57BL6 x DBA/2 mice to benzene in air their number of bone marrow fibroblastoid precursor cells, CFU-F, was determined. The CFU-F exhibited an increasing plating efficiency, giving rise to a larger number of colonies and to colonies of greater size. This effect was dose dependent. When the mice were exposed for 16 weeks and were then allowed to rest, their CFU-F plating efficiency returned to normal within 6 weeks, but then increased again. Hematopoietic stem cells, such as CFU-S and CFU-C exhibited a dose-dependent depression. The in vitro exposure of bone marrow cells to benzene metabolites resulted in a dose-dependent depression of CFU-F numbers.