There are several scientific approaches for the determination of cellular growth influences of known or novel substances under in vitro conditions, among which colourimetric absorption measurement is considered to be one of the convenient methods. [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] (MTS) assay is one of the commonly used colourimetric absorption assays based on the ability of
dehydrogenase from viable cells to produce the brown soluble
formazan detectable at 490 nm. Here we have tested the possible growth influence of
iron (II) sulphate on two human
cancer cell lines, the K562 chronic myelogenous leukaemia and T47D
breast carcinoma cells, based on the MTS assay. We found that
iron (II) sulphate possessed an inhibitory effect when added at 16- to 125-microM concentrations, but
iron (II) sulphate became growth stimulatory when its concentration was further increased to 1000 microM. In addition, a dose-dependent increase in absorbance at the same wavelength was observed when we repeated the experiments without the addition of MTS and
phenazine methosulfate. When we further repeated the cell growth determinations using
adenosine triphosphate content assay for K562 and
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for T47D,
iron (II) sulphate showed a consistent dose-dependent growth inhibitory effect. Morphological investigation after
methylene blue staining clearly demonstrated that
iron (II) sulphate, at a concentration of 1000 microM, is cytotoxic to T47D cells. Interestingly, a consistent increment for the absorbance at 490 nm was further observed with increased
iron (II) sulphate concentration either in the presence or absence of MTS even in a cell-free environment. Thus we conclude that
iron (II) sulphate is actually growth inhibitory and even cytotoxic at high concentrations towards the K562 and T47D
cancer cells and the paradoxical proliferative activity of
iron (II) sulphate on these two
cancer cell lines using the MTS assay was solely due to the oxidation of initial pale green
iron (II) to brownish
iron (III) during incubation in the aqueous condition.