[Heavy metal toxicity in mammalian cell cultures (author's transl)].

Static suspension cultures of L-A cells, a subline of L 929 mouse fibroblasts, were exposed to inorganic metal salts (chlorides). There was an increasing cytotoxicity from lead over mercury to cadmium as determined by reduction of viability and inhibition of proliferation. After 7 days' exposure the LD50 of lead was approximately 3 X 10(-4) M, of mercury 5 X 10(-5) M, and of cadmium 1.3 X 10 (-5) M. The doses causing a 50% inhibition of increase in cell number (ID50) after 7 days' application were determined as follows: 4 X 10(-5) M for lead, 1.3 X 10(-5) M for mercury, and 7.5 X 10(-6) M for cadmium. The biological effects of lead during chronic exposure were studied in more detail. Under continuous presence of the heavy metal the cells developed lead resistance, even to concentrations approaching the LD50. However, the proliferation rates of cells tolerating 1.4 X 10(-4) M were slightly, and of those tolerating 2 X 10(-4) M were clearly reduced as compared to the non-resistant (parent) cells. Cultivation of the resistant cells over 46 days (maximally 60 generations) in lead-free medium lead to a considerable loss of tolerance; this finding indicates that the induced lead resistance is caused by adaptation rather than by mutation and selection.