Neutral red test

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The neutral red test (also NRU test, abbreviation for English neutral red uptake ) is evidence of the determination of cell viability . Cells are treated in vitro with the dye neutral red in order to measure their viability or the proportion of living cells in comparison to a control sample of cells. The NRU test is a standard cytotoxicity test that has been included in the OECD guideline for testing chemicals.

The test is based on the absorption of the dye neutral red into the lysosomes of vital cells. The slightly cationic dye (uncharged at pH 7.4) enters the cells through endocytosis and diffusion and is there bound to anionic residues of the lysosomal membrane. Neutral red has the property that it becomes an ion in an acidic environment and turns red. The pH value in the lysosomes is below five and the dye can no longer leave the lysosome as an ion ( ion trap ). The cell lawn now appears red even to the naked eye. In damaged cells, the ability to take up and bind neutral red may be reduced if, for example, changes in the cell membrane and a disruption in the lysosomal membrane occur as a result of exposure to pollutants . Dead cells are not stained because they no longer have intact lysosomes. Based on the amount of neutral red that has been absorbed or bound, a distinction can be made between living, damaged and dead cells.

literature

  • R. Lullmann-Rauch: Drug-induced lysosomal storage disorders. In: Front Biol. 48 (1979), pp. 49-130.
  • Z. Nemez et al: The pharmacological relevance of vital staining with neutral red. In: Experentia. 35: 1475-1476 (1979).
  • H. Babich, E. Borenfreund: Cytotoxicity of T-2 toxin and its metabolites determined with the neutral red cell viability assay. In: Appl. Environ. Microbiol. 57 (1991), pp. 2101-2103.
  • E. Borenfreund, JA Puerner: A simple quantitative procedure using monolayer cultures for cytotoxicity assays (HTD / NR90). In: Journal of Tissue Cultures Methods. 9: 7-9 (1984).
  • E. Borenfreund, JA Puerner: Toxicity determined in vitro by morphological alterations and neutral red absorption. In: Toxicology Letters. 24: 119-124 (1985).

swell

  1. ↑ OECD (2004), Test No. 432: In Vitro 3T3 NRU Phototoxicity Test, OECD Guidelines for the Testing of Chemicals, Section 4. OECD Publishing. doi : 10.1787 / 9789264071162-en