Quantification of Cytotoxicity by Cell Volume and Cell Proliferation

A fast and sensitive method for the quantification of cytotoxicity, using the cell counter and analyser system, CASY 1, was established. This system has a high resolution and a large dynamic range of volume determination, permitting the volume changes caused by cytotoxic effects to be measured in a reproducible and standardised manner. As a first approach, eight cytotoxic compounds with different modes of action were investigated. For seven of the compounds, changes in the mean cell volume could be demonstrated after three hours. All eight compounds showed a dramatic decrease in mean cell volume within 24 hours. Depending on the degree of membrane destruction caused by the direct or indirect actions of the cytotoxic compounds, values for the mean cell volume between the size of an undamaged cell and the size of the cell nucleus were determined. In addition, the number of living cells was substantially decreased by exposure to the chemicals. Both of the effects of cytotoxic compounds can be detected by following a single parameter, i.e. total cell volume. This parameter is highly sensitive for the detection and quantification of cytotoxicity. IC50 values were within the range obtained in testing by other methods. Cytotoxicity testing by CASY 1 is recommended when highly reproducible measurement is necessary, but the system is also valuable for cell counting and volume determination.