The Involvement of Kupffer Cells in Carbon Tetrachloride Toxicity

Carbon tetrachloride (CCl 4) is a classical pericentral hepatotoxicant; however, precise details of its mechanism of action remain unknown. One possibility is that Kupffer cells participate in this mechanism since CCI4 elevates calcium, and the release of toxic eicosanoids and cytokines by Kupffer cells is calcium-dependent. Therefore, these studies were designed to evaluate the role of Kupffer cells in CCl 4 toxicity in the rat in vivo. Kupffer cells were destroyed selectively with gadolinium chloride treatment (10 mg/kg GdCl 3 iv) 1 day prior to administration of CCl 4 (4 g/kg ig). Twenty-four hours after CCl 4 treatment, rats were anesthetized, blood samples were drawn for aspartate aminotransferase (AST) determination, which is indicative of parenchymal cell damage, and trypan blue was infused into the liver to stain the nuclei of dead hepatocytes. AST levels were in the normal range and trypan blue staining was negligible in livers from vehicle- or GdCl 3-treated rats. As expected, CCl 4 treatment alone elevated AST levels to values over 4000 U/liter and caused massive cell death (60-90 trypan blue-positive cells/ pericentral field). In dramatic contrast, the elevation in AST and cell death due to CCl 4 were almost completely prevented by GdCl 3 treatment. In attempts to understand this phenomenon, metabolic and detoxification pathways were assessed. CCl 4 is metabolized via cytochrome P450 II.E. 1; however, GdCl 3 treatment did not alter this pathway as assessed from p-nitrocatechol formation from the selective substrate, p-nitrophenol. GdCl 3 treatment also had no effect on hepatic glutathione levels. On the other hand, GdCl 3 treatment significantly reduced infiltration of neutrophils resulting from exposure to CCl 4. These data clearly support the hypothesis that Kupffer cells participate in the mechanism of toxicity of CCl 4 in vivo, possibly by release of chemoattractants for neutrophils.