Figure 1  Cytotoxic effects of ALA. Human hepatocarcinoma cell lines (HEP G2 (circles) HEP 3B (squares)) were grown in the absence or in the presence of increasing ALA concentrations (0.5 to 5 mM) and the viability of cells was determined by the MTT assay. Viability was expressed in terms of population growth, as percent of an untreated control population with standard error of the mean (SEM).