Mechanism of Early Carbon Tetrachloride Toxicity in Cultured Rat Hepatocytes

Abstract

CCl, causes liver necrosis in a dose-dependent manner in v i m However, we found that primary rat hepatocytes in culture were killed after a 2 hr incubation with carbon tetrachloride gas at CC14 partial pressures above a threshold between 45 and 54 mmHg. Below this threshold concentration no increase in hepatocyte death was observed. We sought to explain the very abrupt C C 4 concentration threshold for hepatocyte death. Two inhibitors of cytochrome P450 2E1, cimetidine and diallyl sulfide, inhibited lipid peroxidation as measured by production of isoprostanes, but did not reduce hepatocyte death from CC4. At 37", CCI, accelerated the mitochondrial permeability transition in vitro, at a threshold C C 4 concentration similar to that which caused hepatocyte death. Phospholipase A2 inhibitors, mepacrine and 4bromo-phenacyl bromide, inhibited the increase in mitochondria1 permeability, but did not inhibit hepatocyte death caused by CC,. Rat liver microsomal lipids were used to make liposomes loaded with Ponceau Red (FW 760.6). No leakage of Ponceau red was found at CCI, concentrations greater than the threshold for cell death. However, CC4 caused acceleration of liposome fusion, over the C C 4 concentration range spanning the threshold for hepatocyte death. Early hepatocyte death in cell culture is independent of metabolism of CC,, and may be related to direct effects of CC14 on intracellular membranes.

Hepatoprotective activity of Sapindus mukorossi and Rheum emodi extracts: In vitro and in vivo studies

“…The hepatotoxic effects of CCl4 are attributed to its metabolism by P450 to yield toxic trichloromethyl radicals that can act as free radical initiators [28] . These radicals are believed to induce injury either by interacting with the unsaturated fatty acids of cell membranes, thereby causing lipid peroxidation, or by binding covalently to important macromolecules such as proteins, lipids, or DNA [29,30] .…”

Hepatoprotective and Antioxidant Effect of Pisonia aculeata L. against CCl4-Induced Hepatic Damage in Rats

“…The hepatotoxic effects of CCl 4 are largely due to its active metabolite, trichloromethyl radical [16]. These activated radicals bind covalently to the macromolecules and induce peroxidative degradation of membrane lipids of endoplasmic reticulum rich in polyunsaturated fatty acids.…”

Interaction of cimetidine with P450 in a mouse model of hepatocarcinogenesis initiation

“…Johnston and Kroening (1998) have observed that CIM inhibited LP in primary rats hepatocytes in culture but it did not reduce hepatocyte death induced by CCl 4 . We have found here that CIM alone did not produce any alteration in the LP index.…”