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Utilization of rat lymphocytes for the in vitro chromosomal aberration assay.

In vitro cytogenetic assays are widely conducted to assess the mutagenic potential of chemicals. Chinese hamster ovary (CHO) cells or human lymphocytes are often used for these assays; however, these cell types have certain limitations. In order to evaluate an alternate cell system, cultured rat lymphocytes were treated for 4 h at 48 h of incubation with a variety of direct- and indirect-acting clastogens in the presence or absence of an exogenous mammalian activation system. Cytogenetic effects of in vitro physiological alterations such as medium hypertonicity or pH changes were also evaluated. The background aberration rate of rat lymphocytes is approximately 2%, and they respond positively to both direct- and indirect-acting clastogens. In contrast to CHO cells, however, neither the hyperosmolality nor pH changes in the treatment media have significant effect on background aberrations. Unlike samples of human blood, rat blood can be collected under well-controlled environmental conditions. Because of the easy access to rat blood samples, the simplicity of culture, the reproducible nature of its in vitro growth, the positive response to known clastogens and negative response to media pH changes or hyperosmolalities, the rat lymphocyte in vitro chromosomal assay presented is an optimal system to assess the mutagenic potential of chemicals.