The effect of mental-serum complexes on differentiating muscle in vitro.

An investigation has been made of the effect on differentiating cultures of chick myoblasts of the complexes formed on solution in serum of the carcinogenic metals cobalt, nickel and cadmium. Cadmium-serum was the most toxic; a concentration of the complex equivalent to 22·5 μg ions Cd/l killed the cultures within 4 days whereas a comparable effect with cobalt or nickel was observed only at concentrations above 80 μg ions/l. Cultures treated with any of these complexes formed syncytial masses rather than the normal muscle straps produced in control cultures; some of the syncytia appeared to be unstable, breaking down to release individual cells. Addition of the complexes to cultures containing differentiating muscle straps did not cause the release of free cells from these. A zinc-serum complex was less toxic than those of the carcinogenic metals, causing some degeneration only at concentrations approaching 150 μg ions Zn/l; it did not cause the production of abnormal syncytial structures. At levels of 40-80 μg ions Zn/ml this complex gave some protection against the toxicity of the others. Since some of the effects of the complexes of the carcinogenic metals mirror the early stages of carcinogenesis by cobalt, it is suggested that this culture system could provide a means of analysing the processes involved in the malignant transformation of muscle.