An Effect of benzene on Chromosomes in Bone Marrow Cells of Rats

Kim, Kwang Hoe; Oh, Seung Hwan; Shin, Tai Sun

Abstract

The toxic action of benzene on erythropoiesis and myelopciesis, has been recognized since the early years of the present century. With the advance in high civilization and modern covenience, benzene as a kind of aromatic compound has been used for industrial solvent and its longstanding use has committed a public nuisance to be overcome by medical approach. Chromosomal breakage and rearrangement may be produced by radiation, radiomimetics, virus infection and various chemicals, especially, antibiotics and antitumor agent, causing chroimosomal rearrangement in vitro, whose teratogenic action in rats was previously demonstrated. Several works hsve been published on the chromosome damage as a consequence of benzene intoxication. Recently, it was shown by certain workers that individuals who had been exposed to atmospheric benzene, even without haematological disorders, might have an elevated percentage of structural chromosome aberrations in the lymphocytes cultured from their peripheral blood. Moreover, structural and numerical chromosome aberrations were demons trated in patients with blood disorders which were believed to be due to exposure to beuzene vapors. Accordingly, much interest has been paid to its cytologic effect on the hematopoietic tissues in man and experimental animals. A high incidence of chromosomal aberrations has also been found in rabbits exposed to benzene during a period of peripheral pancytopenia and after hematologic recovery. The significance of these findings was discussed in relation to leukemic transition and to their diagnostic value in human benzene intoxication. Chromosomal anomalies can also be induced by benzene given subcutaneously to rata. A pronounced individual variation of the degree of chromosome damage was shown. The purpose of this investigation was to determine whether benzene could a direct effect on the chromosome complement of mammalian bone marrow cells in vivo and whether characteristic banding patterns might be demonstrated in rat chomosomes by a modified trypsin-Giemsa method. Four-week old Sprague-Dawley strain rats of both sexes(each weighing about 50gm) were used for this experimental study. Three groups of animals were treated-with subcutaneous infections of pure benzene. Group I received benzene, 2.0ml per kg body weight, 24 hours before sacrifice; Group II, 48 and 24 hours and Group III, 72, 48 and 24 hours. A control group was given no treatment. The animais were sacrificed in ether anesthesia. Femur and iliac bone marrow cells were suspended in medium 199 within 30 minutes and transferred to warm Hanks-distilled water(1:3) for hypotonic treatment(10 minutes). A freshly prepared solution of methanol glacial acetic acid (3:1) was used as fixative. Finally, a few drops of the cell suspension were placed on moistened, pre-cleaned slides being dried by rapid-drying technique. The slides were stained with either simple Giemsa or trypsin Giemsa banding technique. From the data obtained, this report was summarized as follows: 1. For the benzene-treated groups, chromosomal aberration rate was 13.4% in group II and 38.6% in group III, while in the controls the rate was 6.4 percent. 2. Numerical aberrations included aneuploidy, polyploidy and monoploidy. The most frequent type was hypodiploidy (5.8-9.4%) in all the treated groups. 3. Structural aberrations could be divided in gaps, ring chromosomes, breaks, deletions, exchanges and dicentrics. Among those, the majority of abnormal metaphases was gaps; 2.4%, 2.2% and 10.8% in group I, II and III respectively, and 1. 6% in control group. 4. The translocations and dicentrics were not demonstated in group I and II. 5. The normal chromosome set of the Sprague-Dawley rat was comprised of 42 chromosomes: 20 pairs of autosomes, and one pair of sex chromosomes, xx or XY chromosomes. The total number of major bands in s chromosome complement was about 40 and minor bands, 13, 6. Sucessful demonstration of banding patterns was available by proper adjustment of the concentration, temperature and duration of trypsin solution.

An Effect of benzene on Chromosomes in Bone Marrow Cells of Rats

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