EFFECT OF HIGH POLYOL CONCENTRATIONS ON THE NEUTRAL RED ABSORPTION ASSAY AND TETRAZOLIUM MTT TEST OF RAT HEPATOCYTES IN PRIMARY CULTURE

The effects of three polyols, mannitol, sorbitol and xylitol, on prima ry cultures of rat hepatocytes were studied with the aid of two cytoto xicity markers, the MTT test and the neutral red assay. A dose-related increase in the uptake of neutral red (up to approximately 60%) was o bserved in comparison with untreated cells, whereas the MTT test was u naffected by concentrations of polyols up to 330 mM (620 mOsmol/litre) . The increase in neutral red uptake does not indicate cellular toxici ty as it was reversible and was shown to be due to an increase in the size of lysosomes. For compounds acting on cellular metabolism, such a s phenol, mercuric chloride and pentobarbital, it was shown that the i ncrease in neutral red uptake may minimize any cytotoxic effect of the se compounds. The neutral red assay should therefore be used with caut ion when testing compounds that provoke lysosomal swelling. We recomme nd the use of multiple, mechanistically different, cytotoxicity marker s for the evaluation of xenobiotic cytotoxicity.