Validation of the red blood cell test system as in vitro assay for the rapid screening of irritation potential of surfactants.

An in vitro red blood cell assay (RBC assay) is presented that allows one to estimate irritation potentials of tensides and detergents. The estimation is based on the differentiation between cell membrane lysis and cell protein denaturation. Both effects are measured photometrically by use of the inherent native dye oxyhemoglobin (HbO2). Besides hemolysis (H50) as a test parameter, the denaturation index DI is introduced, which is defined to be equal to 100% at a concentration of 30 mol sodium dodecylsulfate (SDS) per mole HbO2 as internal standard. The HbO2 release (H50), its denaturation (DI), and the ratio of both parameters (L/D ratio) are used to characterize the in vitro effects of surfactants. All data, including the L/D ratio are compared with in vivo data on eye irritancies, evaluated according to OECD Guideline #405 for testing chemicals, and with other published results from in vivo experiments. The good correlation of the L/D ratio of a broad range of 100 marketable shampoos with their corresponding Draize data (r = .806, p less than .0001) allows one to predict eye irritation potentials from another 20 commercially available shampoos in a blind trial with highly significant rank correlations to their in vivo irritancies (rs = .911, p less than .0001). Nearly similar good correlations were obtained by comparing ranks of in vivo and in vitro data of 16 anionic surfactants. All correlations found were significant (rs greater than .80 and p less than .0001). The RBC assay is an inexpensive, rapid, irritancy screening test that provides reliable results with good reproducibility. The test helps to reduce or even avoid animal testing in this application.