title: MTT-assay and neutral red release (NRR)-assay: relative role in the prediction of the irritancy potential of surfactants.
abstract: A comparative study on the in vitro and in vivo irritancy of anionic, amphoteric and non-ionic surfactants was performed. In vitro ED50 values of the surfactants were determined by two cytotoxicity assays, the dimethylthiazoldiphenyltetrazoliumbromide (MTT) assay and the neutral red release (NRR) assay on serum-free cultured human foreskin keratinocytes. In vivo human irritancy data were obtained by a 24 hour occlusive patch test in volunteers and the irritant skin response quantified by visual scoring, evaporimetry and colorimetry. A close relationship between the evaluation methods of the patch test was observed (r = 0.92 to r = 0.96), confirming that the 'bioengineering' methods, such as evaporimetry and colorimetry are suitable for measuring skin irritation. For six surfactants evaluated we found a good correlation (r = 0.91) between the ED50 values of the MTT assay and the in vivo irritancy data. The NRR assay yielded less satisfactory correlation coefficients with regard to MTT assay (r = 0.42) and in vivo irritancy data (r = 0.46). This can be mainly attributed to a misinterpretation of the amphoteric and non-ionic surfactants by the NRR assay. While the NRR assay may better evaluate the anionic surfactants, the MTT assay seems to be more suitable when testing a broader range of chemically diverse surfactants. Limitations of cell culture systems are noted, although the potential usefulness of cultured human skin cells for skin irritancy testing has been clearly demonstrated.
authors.affiliation: Dermatologische Klinik und Poliklinik, Ludwig-Maximilians-Universität, München, F.R.G.
authors.forename: H C
authors.initials: HC
authors.lastname: Korting
authors.forename: S
authors.initials: S
authors.lastname: Schindler
authors.forename: A
authors.initials: A
authors.lastname: Hartinger
authors.forename: M
authors.initials: M
authors.lastname: Kerscher
authors.forename: T
authors.initials: T
authors.lastname: Angerpointner
authors.forename: H I
authors.initials: HI
authors.lastname: Maibach
mesh_terms: D000328:Adult; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003124:Colorimetry; D004396:Coloring Agents; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007509:Irritants / Q000633:toxicity*; D008297:Male; D008875:Middle Aged; D009499:Neutral Red; D012867:Skin / Q000187:drug effects*; D013501:Surface-Active Agents / Q000633:toxicity*; D013778:Tetrazolium Salts; D013844:Thiazoles; D014116:Toxicology / Q000379:methods
chemical_list: D004396:Coloring Agents; D007509:Irritants; D013501:Surface-Active Agents; D013778:Tetrazolium Salts; D013844:Thiazoles; D009499:Neutral Red; C022616:thiazolyl blue