Interlaboratory validation of the in vitro eye irritation tests for cosmetic ingredients. (5) Skin(2)(TM) ZK1100 and tissue equivalent assay

Skin(2TM) ZK1100 (ZK1100) assay and tissue equivalent assay (TEA, Skin(2TM) ZK1200) are human dermal models. These assays were evaluated as alternativ es to the Draize eye irritation test (Draize test) in rabbits. Thirty-nine cosmetic ingredients were selected and used as test substances. The ZK1100 assay was conducted according to an original protocol provided by Advanced Tissue Sciences, a kit supplier. The TEA assay followed a protocol develope d by Osborne er al. (1995). Coefficients of variation (CV) ranged from 11.7 to 133 in results from the ZK1100 assay; three test substances showed the CVs more than 100. These were cetyltrimethylammonium chloride (S3-7), domip hen bromide (S3-11) and di(2-ethylhexyl) sodium sulfosuccinate (S3-14). Aci d Red 92 (S2-3) was excluded from data analysis because its absorbance inte rfered with the endpoint of ZK1100 assay. The CVs from the TEA assay ranged from 31.8 to 119; two test substances showed the CVs more than 100. These were acetic acid and glycolic acid (S3-13). Butanol (S3-9) was excluded fro m the analysis because it was assumed to volatilize during a sample prepara tion. Pearson's coefficient of correlation with maximum average Draize tota l score (MAS) and 24 hr score from the Draize tests were -0.71 and -0.72 fo r the ZK1100 results and -0.63 and -0.60 for the TEA results. When a MAS of 15 was set as a breakpoint for the classification of eye irritancy on Coop er's plots comparing the in vitro and the Draize data, the ZK1100 results s howed five false positives and four false negatives; the TEA results showed three false positives and no false negatives. (C) 1999 Elsevier, Science L td. All rights reserved.