I. Witte et al., SUITABILITY OF DIFFERENT CYTOTOXICITY ASSAYS FOR SCREENING COMBINATION EFFECTS OF ENVIRONMENTAL CHEMICALS IN HUMAN FIBROBLASTS, Toxicology letters, 87(1), 1996, pp. 39-45
Cytotoxicity screening assays measuring survival, growth, colony formi
ng ability, DNA and protein synthesis in human fibroblasts were tested
for their suitability to determine combination effects. Thereby, the
dose-response curves of a hydrophilic substance A alone and after pret
reatment with a membrane damaging substance B were compared. Substance
s B were applied at concentrations which did not induce toxic effects
in the assays (noec). Synergistic combination effects were demonstrate
d by reduction of the EC(20) value of substances A in the combination
in comparison to substances A alone. The following substance pairs (su
bstance B/substance A=membrane damaging/hydrophilic) were tested: n-do
decylbenzenesulfonic acid/2,4-dichlorophenoxyacetic acid, 2,4,6-trichl
orophenol/2,4-dichlorophenoxyacetic acid, 1,1,2,2-tetrachloroethane/4-
chloroaniline pentachlorophenol/CrCl3. While survival, growth, and DNA
synthesis assays were suitable methods for detecting synergistic comb
ination effects, the growth assay was the most sensitive. Here, all fo
ur substance pairs showed synergistic combination effects.