2‐Bromopropane‐Induced Hypoplasia of Bone Marrow in Male Rats

2‐Bromopropane‐lnduced Hypoplasia of Bone Marrow in Male Rats: Tamie Nakajima, et al. Department of Hygiene, Shinshu University School of Medicine—The hematotoxicity of 2 ‐bromopropane was investigated in thirty‐six male Wistar rats. The rats were put into four groups: three groups were exposed to 0, 300, and 1,000 ppm 2‐bromopropane for 8 hr per day, for 9 weeks, respectively, and the remaining group was exposed to 3,000 ppm only for 9‐11 days. Hematotoxicity was assessed by measuring peripheral blood cells as well as cellularity, the number of megakaryocytes and morphological findings in the bone marrow. Exposure to 2‐bromopropane decreased the numbers of erythrocytes in the peripheral blood at 300 ppm or higher, leukocytes at 1,000 ppm, and platelets at 300 and 1,000 ppm. Exposure to 300 ppm 2‐bromopropane did not influence the indices of bone marrow toxicity. Exposure to 1,000 ppm 2‐bromopropane or a higher dose‐dependently induced a hypoplastic profile with replacement of fatty spaces in the bone marrow, though the durations of exposure to 3,000 ppm were under one sixth. These exposures also induced dose‐dependent decreases in the number of megakaryocytes, with the maintained ratio of granulocytes to erythrocytes in the bone marrow. Residual progenitor cells showed some dysplastic or megaloblastic changes. These results suggest that exposure to 2‐bromopropane leads to a reduction in the numbers of hematopoietic cells in the bone marrow, the result being a persistent pancytopenia in male rats.