The suitability of hepatocyte culture models to study various aspects of drug metabolism

Since the liver is the main organ involved in the metabolism and the toxici ty of xenobiotics, isolated rat hepatocytes have been increasingly used in recent years as a model to identify pharmacological and toxicological respo nses of drugs. However; it is generally recognised that isolated hepatocyte s retain most of their functions only for a short period. Fo, this reason, numerous models and techniques have been developed to study and improve the metabolic capacity of hepatocytes in vitro, over an extended time period a nd in application for drug metabolism studies. In the present study, we com pared four different cell culture models to fulfill these requirements and have therefore harvested hepatocytes and cultured them in different culture systems over two weeks. In order to prove certain advantages of disadvanta ges of each model, we compared the metabolic capacity, albumin secretion, t he release of cytosolic and mitochondria enzymes, as well as the capacity t o metabolise diclofenac (DF). We found that rat hepatocytes in all studied culture models (except the Uni syn Bioreactor) were able to metabolise DF to the same extent as found in v ivo. However; the concentration of metabolites was found to decrease with c ulture time using the monolayer although the DF metabolite level in the col lagen Sandwich culture was higher than that of the monolayer culture. The 3 D-membrane bioreactor preserved the metabolic capacity for a prolonged peri od of time. The concentrations of DF metabolites in the Unisyn hollow fiber bioreactor were below the detection limit, which corresponded to other par ameters such as albumin secretion and cytochrome P450 activity, disqualifyi ng this culture system clearly for the use of in vitro primary hepatocyte c ultures. The other three systems all have their place in drug metabolism wi th different advantages. However; our studies clearly showed that hepatocyt es cultured within a collagen sandwich or in the 3D-membrane bioreactor qua lify to study various aspects of drug metabolisms over a long time period. Further studies are needed to prove if the later two culture models may rea lly help to reduce animal testing.