Liver Damage, Carbon Tetrachloride, PeroxidationCCl4-induced liver damage was modeled in monolayer cultures of rat primary hepatocytes with a focus on involvement of covalent binding of CC14 metabolites to cell components and/ or peroxidative damage as the cause of injury.(1) Covalent binding of 1 4 C-labeled metabolites was detected in hepatocytes immediately after exposure to CC14. (2) Low oxygen partial pressure increased the reductive metabolism of CC14 and thus covalent binding. (3) [1 4 C]-CC14 was bound to lipids and to proteins throughout subcellular fractions. Binding occurred preferentially to triacylglycerols and phos pholipids, with phosphatidylcholine containing the highest amount of label. (4) The lipid peroxidation potency of CC14 revealed subtle differences compared to other peroxidative substances, viz., A D P-Fe3+ and cumol hydroperoxide, respectively. (5) CC14, but not the other peroxidative substances, decreased the rate of triacylglycerol secretion as very low density lipoproteins. (6 ) The anti-oxidant vitamin E (a-tocopherol) blocked lipid peroxidation, but not covalent binding, and secretion of lipoproteins remained inhibited. (7) The radical scav enger piperonyl butoxide prevented CCl4-induced lipid peroxidation as well as covalent bind ing of CCI4 metabolites to cell components, and also restored lipoprotein metabolism.The results confirm that covalent binding of the CC13* radical to cell components initiates the inhibition of lipoprotein secretion and thus steatosis, whereas reaction with oxygen, to form CCI3 -O O * , initiates lipid peroxidation. The two processes are independent of each other, and the extent to which either process occurs depends on partial oxygen pressure. The former process may result in adduct formation and, ultimately, cancer initiation, whereas the latter results in loss of calcium homeostasis and, ultimately, apoptosis and cell death.