PREVALIDATION OF THE EPIDERM PHOTOTOXICITY TEST (ED-PT).
The EpiDerm™ phototoxicity test was chosen for prevalidation within ECVAM’s tiered prevalidation procedure. In phase 1, ZEBET drafted an SOP and project plan for conducting the study. ZEBET’s task in phase I was to adapt the existing Skin2 methodology to the specific needs of the epidermal model EpiDerm. UVA sensitivity experiments revealed 6J/cm2 as the highest non-cytotoxic UVA dose and exposure to test materials for 3, 6, and 21 hours before UVA irradiation revealed 21 hours to be the optimum exposure time. Established phototoxins were used to evaluate the method and were correctly identified. In phase II, taking into account the patch technique used in vivo, the three participating laboratories amended this technique and evaluated its usefulness for the EpiDerm test. Results revealed that the patch technique was useful for chemicals applied in oil but not in water. Since reproducibility of the data within, and between, the laboratories was excellent, it was decided to proceed to phase III. In phase III, ZEBET drafted the final SOP and BIBRA selected ten chemicals for the blind trial. Each of the chemicals was tested twice independently in each laboratory and the data were submitted for biometrical analysis, which confirmed the expected predictivity and robustness of the test; only one positive chemical (tetracycline) was not detected as a phototoxin and none of the negative chemicals was over predicted as a phototoxin. We conclude that the ED-PT 1) meets the criteria previously determined for the Skin2 PT, 2) allows use of complex matrixes, 3) is an adjunct test to the 3T3 NRU PT, 4) is ready to undergo formal validation.
ECVAM, EpiDerm, Patch technique, Phototoxicity, Pre-validation, Prevalidation, Reproducibility, Reproducible, Sun screens, UVA, UVB, Ultraviolet radiation (UV), Validation
5-methoxypsoralen (5-MOP), 4-methylbenzylidene camphor (S 60), 8-methoxypsoralen (8-MOP), Acridine hydrochloride, anthracene, Bergamot oil, Chlorpromazine (CPZ), Lauryl sulfate sodium. Neutral red. Octyl methoxy cinnamate (S 28), Octyl salicylate (S 13), Penicillin G, Promethazine (PMZ), Tetracycline free base
Request a copy of this paper, click here.