Effects of benzene inhalation on murine pluripotent stem cells

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Abstract
Effects of benzene inhalation on mouse pluripotent hematopoietic stem cells were evaluated. Male mice 8-12 wk old were exposed to 400 ppm benzene for 6 h/day, 5 days/wk, for up to 9.5 wk. At various time intervals exposed and control animals were killed and cardiac blood was evaluated for changes in white blood cell (WBC) and red blood cell (RBC) content. Femora and tibiae were evaluated for total marrow cellularity, stem cell content (as measured by the spleen colony technique) and the percent of stem cells in DNA synthesis (as determined by the tritiated thymidine cytocide technique). Exogenous spleen colonies grown from marrow of exposed animals were counted, identified and scored by histological type. Exposure to benzene caused significant depressions of RBC and WBC throughout the exposure period, which continued for at least 14 days after exposure. Bone marrow cellularity and stem cell content were also depressed in exposed animals. Tritiated thymidine cytocide of spleen colony-forming cells was generally increased in exposed animals, indicating a compensatory response to the reduction of circulating cells. Spleen colonies of all types were depressed after exposure to benzene. The significance of the reduction in cellularity, stem cell content and changes in morphology of spleen colonies was discussed in relation to cellular toxicity and residual injury.