Jirova, D., Kristina, K., H. Endova, H. Kolarova and R. Kubinek. The 3T3 Neutral Red Uptake Phototoxicity Test in the Czech Republic. ATLA 1999. 27: 338.

The latest studies conducted by EU/COLIPA have shown that the in vitro 3T3 cell neutral red uptake phototoxicity 3T3 NRU PT) test is a scientifically validated, sensitive and robust alternative phototoxicity test (Spielmann et al. ATLA 22, 314-348, 1994). We have introduced this method in the Czech Republic for standard chemicals recommended in validation studies. We have studied the toxic effects of UVA and UVB radiation in 3T3 cell culture using separate Philips tubes TL-D 18/08 (320-400 nm) for UVA and TL 20/12 RS (280-320 nm) for UVB. The cytotoxic effect were determined fluorimetrically using an automated fluorescence reader (Wellfuor-Denley) interfaced with a PC-compatible computer. We have tested three groups of substances (UV-absorbing phototoxic, UV-absorbing non-phototoxic, and non-UV-absorbing non-phototoxic). We have proved the phototoxic effect of known phototoxicants in the UVA region. Although some of the chemicals also exhibit absorption in the UVB region, separate UVB irradiation did not elicit a phototoxic effect. Following the successful introduction of the test system, we have focused on a group of ClAl PcS₂ phthalocyanines and Zn PcS₂ phtalocyanine. This new generation of photodynamic substances developed by the Czech chemical industry is intended for possible application in clinical and hygienic practice. We have proved their low cytotoxic and high phototoxic effects in the UVA region. The in vitro methods were proved to be of great value as a first step in the sequential approach for phototoxicity testing, according to which, in vitro tests should be carried out before considering any animal testing, or tests on humans.