In vitro cytogenetic testing of an organoselenium compound and its sulfur analogue in cultured rat bone marrow cells

Background: Selenium (Se) is a non-metal element, occurring in varying degrees in the environment and it has been found to be a component of several enzymes. Different selenium compounds have been associated with carcinogenicity, toxicity, modification of metal toxicity and prevention of cancer. Organoselenium compounds had substantially greater bioavailability and less toxicity than that of inorganic selenium. From a chemical point of view, Se resembles sulfur (S) in many of its properties, thus, Se and S may be considered to be isosteric. The ability of a synthetic organoselenium compound; cyclopenta-dienyldicarbonyl ironselenoterephthalic acid (CSe) and its sulfur analogue (CS) in the range of 10-8 to 10-5 M, to induce sister-chormatid exchanges (SCE) and alter cell division expressed as mitotic index (MI) as well as cell survival has been investigated. Methods: Rat bone marrow cells were cultured in the presence of CSe and CS in the range of 10- 8 to 10-5 M with a total exposure time of 4, 16 or 28 h at 37?C. Fluorescence-plus-Giemsa (FPG) technique was used to visualize chromosomes for SCE analysis and MI determination. Trypan blue exclusion technique was used to determine cell viability. Results: At the three exposure times, cell survival progressively decreased with increasing concentration, but the effect of either chemical was not significant (ANOVA; P < 0.05) as compared to the negative control. Significant reductions in MI were calculated at the highest concentration (10-5 M) when either chemical was applied for 16 or 28 h. Furthermore, the mean SCE increased with longer exposure times and, in general, CSe had slightly greater effect on cell survival and caused higher frequencies of SCE than CS. The exception was the 10-8 M treatment. However, both CSe and CS failed to induce 2-fold SCE as that of the negative control and therefore they are not considered as mutagens. Conclusion: Both CSe and CS in the range of 10-8 to 10-5 M could not double the SCE rate of the negative control and therefore not considered as mutagens at these experimental conditions.