Residual myelotoxicity of lindane in mice.

Lindane (gamma-1,2,3,4,5,6-hexachlorocyclohexane), a widely used insecticide, may be found at low concentrations in the human diet. Male B6C3F1 mice given lindane daily at doses of 20 and 40 mg/kg body wt by gavage in corn oil for 3 days had suppressed bone marrow cellularity, erythrocyte precursors, granulocyte-macrophage progenitor cells (CFU-GM), and residual progenitor cell damage, which could be demonstrated by two whole-body irradiations (WBI) at 200 rads. Lindane exposure for 10 consecutive days at doses of 0, 10, or 20 mg/kg did not cause clinical abnormality or changes in body weights, but there were dose-dependent decreases in marrow cellularity, in more pluripotent stem cells and in committed CFU-GMs, which returned to control values by 4 weeks. These mice were then subjected to two 100-rad exposures of WBI at 4 and 9 weeks following cessation of lindane treatment. This level of irradiation caused only a transient drop in number of marrow progenitor cells. Control and lindane-exposed mice were examined at 1 and 6 weeks following the last irradiation, which was 10 and 15 weeks following the final lindane exposure. The lindane-exposed mice had lower progenitor cell numbers and slower recovery from the irradiation. These results indicate that lindane has significant myelotoxicity in mice and short-term lindane exposure can induce residual progenitor cell damage that can be demonstrated by subsequent irradiation.