In vitro systems: standardization of endpoints

Principles are discussed for utilizing cell culture systems to assay for interactions between drugs and radiation. Emphasis is based on the necessity of using synchronous cultures to determine whether the interaction is independent, additive, or synergistic, and to determine the effect of drugs on recovery from sublethal x-ray damage (SLD). Furthermore, in studies of drug effects on SLD, adequate controls must be included to distinguish between effects associated with the interaction of 2 x-ray doses and the effects associated with interaction of a second x-ray dose with prior drug exposure. Finally, different methods of expressing drug exposure are reviewed, and associated problems related to predicting in vivo effects from in vitro results are mentioned