Fig. 2.

Toxicity of pentavalent sodium arsenate (As V) was determined by measuring cellular release of lactate dehydrogenase. MEMM cells were exposed to different concentrations of arsenate and, after the indicated time intervals; aliquots of culture medium were removed and assayed for the presence of LDH as described (see Methods). Absorbance of the red formazan product at 490 nm was directly proportional to the extent of cell death. Each bar in a cluster represents a level of absorbance recorded at a different concentration of arsenate ranging from 0 μM (negative control) to 100 μM. The cluster marked “staur.” represents absorbance values from cells treated with 0.1 μM staurosporine (positive control). Results were obtained from four separate experiments performed in triplicate and mean values ± S.E. are plotted for each treatment condition. * p <0.05.