LONG-TERM MAINTENANCE OF DRUG-METABOLIZING ENZYME-ACTIVITIES IN RAT HEPATOCYTES AFTER CRYOPRESERVATION

Recent studies have demonstrated that freshly isolated adult hepatocyt es from various species can be hypothermically preserved for a short p eriod or cryopreserved for a prolonged period before seeding in primar y culture. This study was designed to determine whether rat hepatocyte s could be maintained functional for a prolonged period after either h ypothermic preservation or cryopreservation. Cold storage was carried out in University of Wisconsin solution (UW) and freezing in Leibovitz medium added with 10% fetal calf serum and 16% dimethyl sulfoxide. Ra t hepatocytes were then set up either in pure conventional culture or in coculture with rat liver epithelial cells. Various functions were m easured over 4- and 15-day periods, i.e., albumin secretion rate, deet hylation of ethoxyresorufin and phenacetin, dealkylation of pentoxyres orufin, glucuronidation and sulfoconjugation of paracetamol, and N-ace tylation of procainamide. No major differences were observed between u nfrozen, frozen, and UW-preserved cells. While in pure culture all the functions tested were markedly decreased after 3 or 4 days, they rema ined high over the 15-day period in coculture, being either maintained or increased after 7-12 days compared to initial values. These result s clearly demonstrate that when maintained under suitable culture cond itions, rat hepatocytes can fully recover after hypothermic preservati on or cryopreservation and therefore represent a suitable in vitro mod el system for pharmacotoxicological studies. (C) 1997 Academic Press.