XENOBIOTIC-METABOLIZING ENZYME-ACTIVITIES AND VIABILITY ARE WELL PRESERVED IN EDTA-ISOLATED RAT-LIVER PARENCHYMAL-CELLS AFTER CRYOPRESERVATION

Rat liver parenchymal cells (PC) were isolated by EDTA perfusion and w ere purified by a subsequent Percoll centrifugation. The isolated PC h ad a viability of 95%, as judged by trypan blue exclusion. Freshly iso lated PC were cryopreserved with an opti mized protocol in a computer- controlled freezer. After thawing, the PC still retained a viability o f 89%. The activities of representative xenobiotic metabolizing enzyme s were compared between freshly isolated and cryopreserved PC after th awing. The cytochrome P450 content and the cytochrome P450 2C11 isoenz yme activity, determined by hydroxylation of testosterone in intact ce lls, were not affected by the cryopreservation. The following phase II enzyme activities were also well maintained after cryopreservation: P henol sulfotransferase (92%), 1-naphthol UDP-glucuronosyl transferase (95%), soluble epoxide hydrolase (87%), and glutathione S-transferase (88%), determined with broad spectrum substrate 1-chloro-2,4-dinitrobe nzene. However, there was a significant decrease in plating efficiency between freshly isolated (86%) and cryopreserved (57%) PC when they w ere cultured. The initial quality of the freshly isolated PC is decisi ve for the success of cryopreservation. These results support the use of cryopreserved PC in pharmacology and toxicology with the aim to red uce the number of experimental animals used. (C) 1995 Academic Press, Inc.