Cytotoxicity of manganese for mammalian cells in vitro--comparisons with lead, mercury and cadmium.

The effects of manganese chloride were studied in two human cell lines HeLa and human embryonic diploid fibroblasts in V79 Chinese hamster lung cells, and L-A mouse fibroblasts. Manganese produces a dose-dependent depression of proliferation along with a decrease of the mitotic rate. Effects on viability are accompanied by increased release of the intracellular enzyme lactic dehydrogenase. Lactic acid is stimulated indicating enhanced glycolytic activity. The colony forming ability and the rate of DNA synthesis are inhibited in a dose- and time-related fashion. Comparing these results with those of previous studies of the cytotoxicity of lead, mercury, and cadmium in the same test systems, similar effects are observed, though with different intensities and slight differences between the cell lines. As regards depression of viability, the following rank order of toxicity can be established: Pb2+ < Mn2+ < Hg2+ < Cd2+; as regards reduction of proliferation lead is less and cadmium more effective than manganese, while mercury effects vary depending on the cells tested. Concerning colony formation and DNA synthesis the toxicity of manganese is again higher than that of lead and manganese, especially the influence on DNA synthesis, show immediate recovery after cessation of exposure indicates that the genetic material is not directly involved and that the effects on proliferation colony formation, and DNA synthesis are the consequences of several elaborate processes at the cellular level.