Multivariate factorial analysis of data obtained in seven in vitro test systems for predicting eye irritancy

Seven in vitro test systems used to predict eye irritancy (EYTEX, SIRC cytotoxicity, HeLa cytotoxicity, chorioallantoic membrane (CAM), liposome, red blood cell and haemoglobin denaturation test system) were applied to 12 surfactants, and the results were subjected to multivariate analysis to evaluate the relative contributions of five factors. These factors were: (1) cellular plasma membrane destruction factor, (2) haemoglobin type protein denaturation factor, (3) EYTEX-type protein denaturation factor, (4) cytotoxicity factor and (5) an unknown (unidentified) factor. The results clarified the basis on which the findings of each test system were related to the Draize results. According to the analysis, the Draize eye irritation test could be explained by the contribution of the protein denaturation factor and cellular plasma membrane destruction factor. This provides support for a previous hypothesis that the major mechanisms of eye irritation are cellular plasma membrane destruction and protein denaturation. The CAM test value showed a higher correlation coefficient (0.906) with the Draize score than did the results of any of the other test systems; this was due to the fact that these two tests showed similar patterns of dependence on the five factors as indicated by the factorial analysis. The haemoglobin denaturation test system had the next highest correlation coefficient at about 0.75. Furthermore, by using further tests to make up the deficiency of the other necessary factors, a desirable battery system could be predicted; for example, the combination of the haemoglobin-denaturation and rat red blood cell tests would provide a result similar to that of the Draize test. This study should contribute to the development of a rational basis for prediction of eye irritancy of chemicals using in vitro test systems.