High level benzodiazepine and ammonia clearance by flat membrane bioreactors with porcine liver cells

The onset of hepatic encephalopathy is a multifactorial process in which en dogenous benzodiazepines and hyperammonemia play a pivotal role. The treatm ent of comatose states in liver failure is one of the major functions of a bioartificial liver. A controlled study demonstrating the capacity of a lar ge scale bioartificial liver to detoxify benzodiazepines could be a crucial prerequisite to break this circle of events leading to coma. The aim of th is study was therefore to expose the bioreactor to high levels of benzodiaz epines and ammonia for evaluation of its detoxifying capacity. We have deve loped a novel and unique device reconstructing the plate architecture of th e liver. Porcine hepatocytes were co-cultured with non-parenchymal cells. W e investigated benzodiazepine metabolism using diazepam as model drug. The bioreactor was also loaded with high levels of ammonia and ammonia clearanc e as well as urea secretion with ammonia challenge were investigated. Album in secretion was analysed in parallel as a control viability and tissue spe cific secretory parameter. The results clearly show that the velocity of di azepam turnover increases between day 1 and 2 and stabilises at high levels . Typical diazepam metabolites including temazepam, N-desmethyl-diazepam an d oxazepam were generated. Cell specific functions,including albumin secret ion, were comparable to an in vivo liver. We conclude that the Aat membrane bioreactor used as bioartificial liver has the potential to detoxify diaze pam and ammonia at significant amounts. Maintenance of monoxygenase activit ies in vitro is one of the strongholds of the bioreactor concept presented in this study. (C) 2000 Elsevier Science B.V. All rights reserved.