Phototoxicity

Validated Non-animal Alternatives

The European Centre for the Validation of Alternative Methods (ECVAM) Scientific Advisory Committee (ESAC) endorsed the 3T3 NRU phototoxicity test method¹, stating that "the 3T3 NRU PT is a scientifically validated test which is ready to be considered for regulatory acceptance" (ESAC Statement, Nov. 3, 1997).

OECD TG 432 describes the protocol for conducting the 3T3 NRU phototoxicity test. The assay measures the viability of mouse Balb/c 3T3 cells following their exposure to a chemical in the presence and absence of light. Cytotoxicity (cell death) causes a reduction in the uptake of Neutral Red (a dye) by the cells. The concentration-dependent reduction in dye uptake 24 hours following treatment is used as the assay endpoint, typically the IC₅₀ value (the concentration of test substance that reduces cell viability to 50% of the untreated control value).

¹"Phototoxicity is defined as a toxic response from a substance applied to the body which is either elicited or increased (apparent at lower dose levels) after subsequent exposure to light, or that is induced by skin irradiation after systemic administration of a substance" (OECD, 2004).