Cutaneous toxicity testing in organ culture: Neutral red uptake and reduction of tetrazolium salt (MTT).

Rabbit full thickness skin can be maintained viable for 7 days using a two-compartment organ culture model. We report that this model is useful for assessing cutaneous toxicity. 11 chemicals were each applied topically and then cytotoxicity was determined using two different assays. Mitochondrial activity was assessed by measuring reduction of the tetrazolium salt MTT, while uptake of the vital dye neutral red was used as a parameter of membrane damage. Conversion of MTT was inhibited in a dose-dependent way by all of the chemicals tested except dimethyl sulphoxide. Furthermore, when the skin explants were kept in culture after exposure to the test agents, both repair of initial damage and delayed toxicity could be observed to some extent. Uptake of neutral red was affected dose-dependently by six out of the 11 chemicals tested. The data indicate that a strong correlation exists between the cytotoxicity of chemicals and their effect on the conversion of MTT in skin organ culture. The MTT assay reported here offers the possibility of studying both acute and delayed cytotoxicity, and to some extent, recovery from initial damage.