The comparative mutagenic action of 7,12- dimethylbenz(a)anthracene in the Armenian hamsters and mice

he Armenian hamster (AH), Cricetulus migratorius, was first used in biomedical research by Yerganian and Papoyan (1). This rodent has a low diploid number of 22 chromosomes, like the Chinese hamster, and was analyzed using routine and differential staining (1,2). The AHs are successfully used in mutagenesis studies such as detection of reciprocal translocations in the germ cells (3), chromosomal aberrations induced by cyclophosphamide (CP) and thiotepa in bone marrow cells (4,5). These experiments show the increased resistance of AHs to clastogenic action of drugs and metaphase arresting ability of colchicine compared to mice, rats, guinea pigs and the Chinese hamsters. The aim of our work was to study comparative mutagenic action of strong rodent carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) in AHs and mice. The experiments were performed with AHs, trapped in the region of Yerevan (Armenia) and maintained in our animal room (20 male AHs, weighing 25 g). We used also 20 male random-bred albino mice (22 g b.w.) from animal room of Cancer Research Center, Yerevan (Armenia). The animals were maintained in our animal room on standard rodent diet (specific for each species) and water ad libitum. To study the comparative mutagenic action of DMBA (Fluka, Buchs, Switzerland), the carcinogen was dissolved in olive oil and was injected twice apart intraperitoneally into rodents at doses equal to 1/10 of LD50 (22 mg/kg and 40 mg/kg for mice and AHs, respectively) (6). As a negative control the vehicle of DMBA was used (olive oil). For positive control we used the CP (Mosmedpreparati, Russia) dissolved in saline and injected intraperitoneally at single dose of 25 mg/kg b.w. for mice, and 50 mg/kg for AHs. Bone marrow sampling was done 24 h after the last chemical agent injection and processed as described earlier (7). Slides were stained with acridine orange according to Tinwell and Ashby (8). We used the LM-4 fluorescence microscope (USSR) to observe the slides. Each slide was assessed for micronucleated (MN) polychromatic erythrocytes (PEs) among 1000 erythrocytes. In addition, the per cent content of PE was calculated. Statistical analysis was performed by using Student's t tests. The data concerning MN inducing action of DMBA are presented in Table 1.