Visual and simple determination of glucose-induced acidification by yeast cells: application to rapid cytotoxicity test.

This study demonstrated that glucose-induced proton release from yeast cells was more sensitive to various inhibitors than cell proliferation. In this study the inhibition of glucose-induced proton release was determined on the basis of color change of pH indicator, methyl red, from pH 5 to pH6 at cell density of 2.5 × 10 cells/ml. When yeast cells were incubated with the inhibitors of glucose intake, glycolysis, and plasma membrane H -ATPase for 1 h, these cytotoxic effects were observed by following the change in absorbance at 527 nm due to methyl red for 5 min. The cytotoxic effects of heavy metal ions, detergents and quinones were observed in the same manner. The above method was superior in sensitivity and measurement time to cell proliferation measurement that required 9 h. This visual cytotoxicity test (methyl red test) is expected to be useful as simple and rapid cytotoxicity test with yeast cells.