The effect of three zirconium (Zr) compounds, zirconium oxychloride (ZrOCl₂), zirconium oxide (ZrO₂) and zirconium silicate (ZrSiO₄) on the viability and DNA synthesis of cultured spleen cells from C57BL mice was studied in vitro. The viability of spleen cells was determined by the trypan blue stain method using cells cultured in a CO₂ incubator at 37°C for 1-4 days.
The degree of DNA synthesis of spleen cells was determined by ³H-thymidine incorporation into spleen cells. The viability of spleen cells treated with ZrOCl₂ exhibited similar changes at concentrations of 1-40μM and decreased at concentrations of 80-400μM, as compared with that of control cells.
On the other hand, no effects of ZrO₂ and ZrSiO₄ on the viability of spleen cells were recognized at concentrations of 1-400μM. The degree of ³H-thymidine incorporation into spleen cells treated with ZrO₂ or ZrSiO₄ was not different from that of control cells.
In the case of spleen cells treated with ZrOCl₂, it was enhanced at concentrations of 1-20μM and was inhibited at concentrations of 40-400μM as compared with the control cells.
The results of these studies in vitro suggest the following:
1) The effect of Zr on the cytotoxicity of mouse spleen cells depends upon the solubility of Zr salts.
2) ZrOCl₂ was found to be weakly mitogenic for lymphocytes at a narrow concentration (1-20μM; max, about 10μM) range.