Cell detachment and cloning efficiency as parameters for cytotoxicity.

Cell detachment and cloning efficiency of Baby Hamster Kidney cells (BHK-21 C13) were used as parameters to quantify cytotoxicity in vitro of 3 endogenous chemicals (glutathione, L-methionine, L-cysteine HCl) and 4 organotin compounds (tributyltinoxide, tributyltinchloride, tetrabutyltin, tetraphenyltin). IC50 values (inhibitory concentration at which the cloning efficiency was reduced to 50%) were estimated to be larger than 10(-3) M for all 3 endogenous substances, which served as a calibration of the cell culture system for non-toxic chemicals. For the 2 tributyltin salts the IC50 values were estimated to be near 10(-6) M and for the 2 tetraalkyltin compounds near 10(-5) M. The estimated CD50 values (concentration at which 50% of the cells detach) were at least twice as large as the corresponding IC50 values for all 7 chemicals tested. For the toxic tributyltin salts the cell detachment assay was 30-60 times less sensitive than the cloning efficiency assay. However, both assays rank all compounds tested in the same sequence of toxicity as that known from in vivo studies.