The effects of methylmercury on the cytoskeleton of murine embryonal carcinoma cells.

Immunofluorescence staining with antibodies to tubulin and vimentin and staining with phalloidin have been used to examine the effects of methylmercury on the cytoskeleton of embryonal carcinoma cells in culture. Exposure of embryonal carcinoma cells to methylmercury (0.01 to 10 microns) resulted in concentration- and time-dependent disassembly of microtubules in interphase and mitotic cells. These effects were reversible when cultures were washed free of methylmercury. Spindle microtubules were more sensitive than those of interphase cells. Spindle damage resulted in an accumulation of cells in prometaphase/metaphase, which correlated with a temporary delay in the resumption of normal proliferation rate upon removal of methylmercury. Of the interphase cytoskeletal components, microtubules were the first affected by methylmercury. Vimentin intermediate filaments appeared relatively insensitive to methylmercury, but showed a reorganization secondary to the microtubule disassembly. Actin microfilaments appeared unchanged in cells showing complete absence of microtubules. Our results 1) support previous reports suggesting that microtubules are a primary target of methylmercury, 2) document a differential sensitivity of mitotic and interphase microtubule systems and 3) demonstrate the relative insensitivities of other cytoskeletal components.