In vitro system for the prediction of hepatotoxic effects in primary hepatocytes.

Prediction of liver toxicity and compound responses continues to be a major challenge for the pharmaceutical industry. In vitro studies on liver cells have been developed to reduce or replace animal experiments. However, most of the tests in use are based on cell lines which do not necessarily represent normal cell physiology. We compared the response of primary human hepatocytes from two donors with primary rat hepatocytes and the cell line HepG2 to the test compound acetaminophen (AAP) by measuring oxygen consumption, extracellular acidification and cell adhesion as dynamic parameters of cell metabolism. Primary human hepatocytes were cultured on collagen pre-coated sensor chips or in conventional two-dimensional cultures in chemically defined Human Hepatocyte Maintenance Medium. This medium allows cultivation of functionally differentiated hepatocytes for several weeks. Sensor chip based results were compared with conventional assays for hepatocytes like albumin release and urea release. The hepatocytes were exposed to AAP (50-2815 mg/l) for 24 h. Cell respiration was inhibited by AAP concentrations of 500 mg/l and more in all three cell types, whereas only the cellular acidification rates and cell adhesion of the rat hepatocytes and the HepG2 cells were affected by AAP. In conventional cultures of human hepatocytes, AAP had no effect on cellular viability. Whereas high doses of AAP (2815 mg/l) diminished albumin secretion by 70-80%.