A SELF-REGULATING CELL-CULTURE ANALOG DEVICE TO MIMIC ANIMAL AND HUMAN TOXICOLOGICAL RESPONSES

The overall goal of this project is the development of a new methodolo gy for translating advances in molecular level understanding of toxico logical responses into a predictive tool for dose response in whole an imals and humans exposed to single compounds or mixtures of compounds. The methodology incorporates a mechanistic cellular level model into a PBPK (physiologically based pharmacokinetic) model which simultaneou sly guides the development of an in vitro cell culture analog (CCA) to the PBPK. Where the PBPK specifies an organ, (e.g., liver) the in vit ro or CCA system contains a compartment with the appropriate cell or c ell population (e.g., hepatocytes for the liver). The CCA has signific ant advantages over other in vitro systems and PBPK systems used indep endently for evaluating metabolic responses to drugs or potentially to xic chemicals where the exchange of metabolites between organs is like ly to be important. The CCA system is superior to a PBPK because an a priori description of complete metabolism is not required and secondar y, unexpected interactions can be detected. The CCA system, unlike oth er in vitro systems, gives a dynamic response that realistically simul ates in vivo interactions between organs. Furthermore, the CCA allows dosing on the same basis as animal tests (e.g., milligrams per kilogra m of body mass equivalent). Because the construction of a CCA is guide d by a PBPK, this approach allows extrapolation to low doses and acros s species, including extrapolation to humans. We have constructed a pr ototype system and have conducted proof-of-concept experiments using n aphthalene as a test chemical. These experiments clearly demonstrate t he ability to generate a reactive metabolite in one compartment and de tect its effects (on LDH release and glutathione depletion) in a secon d compartment. However, this prototype device would be expensive to re plicate and requires nearly constant supervision from a trained invest igator. For this concept to replace animals an inexpensive, self-regul ating device is needed. An initial design to accomplish this goal is d escribed as well as the corresponding model using naphthalene as a tes t compound. (C) 1996 John Wiley & Sons, Inc.