Actions of Selected Hepatotoxicants on Freshly Isolated and Cryopreserved Rat Hepatocytes

Abstract

The present study compares the actions of the hepatotoxic agents allyl alcohol, acetaminophen, and carbon tetrachloride on energy metabolism in freshly isolated and cryopreserved rat hepatocytes. After 30 min incubation of freshly isolated hepatocytes at 37°C to allow metabolic equilibration, hepatocytes were supplemented with cryoprotectants and cooled in a stepwise manner to liquid nitrogen temperature. Hepatocytes stored in liquid nitrogen for 2 weeks to 6 months were thawed and centrifuged through Percoll to remove damaged cells. Despite similarities in energy status as indexed by ATP content and the rate of urea synthesis in freshly isolated and cryopreserved hepatocytes, cryopreserved hepatocytes were more sensitive to hepatotoxicants. All three hepatotoxicants caused ATP and rates of urea synthesis to decline to a greater extent in cryopreserved than in freshly isolated hepatocytes. Rates of oxygen uptake were higher in cryopreserved cells than in freshly isolated hepatocytes and declined in cryopreserved cells but not in freshly isolated cells during the initial period of incubation. Rates of mitochondrial respiration stimulated with site-specific substrates were comparable in freshly isolated and cryopreserved cells permeabilized with digitonin. Allyl alcohol and acetaminophen inhibited site-specific respiration to the same extent in both groups of cells. Collectively, these results suggest that increased sensitivity to hepatotoxic agents and elevated oxygen consumption in cryopreserved hepatocytes recovered after storage in liquid nitrogen are related to higher demand for energy in these cells rather than to permanent injury caused by cryopreservation and irreversible uncoupling of oxidative phosphorylation.