Enhancement of carbon tetrachloride-induced liver injury by a single dose of ethanol: proton magnetic resonance imaging (MRI) studies in vivo

Abstract

Magnetic resonance imaging (MRI) and localized magnetic resonance spectroscopy (MRS) were used to study the effects of a single dose of ethanol, given 18 h prior to experiments, on CCl 4-induced acute hepatotoxicity in rats in situ. Localized edema in the centrilobular region of the liver, following exposure to ethanol and CCl 4, was detected by 1H-MRI techniques. The edema was characterized by a volume selective spectroscopy (VOSY) method, which measured an increase in water concentration from ethanol and CCl 4-treated rat livers, in comparison to control livers. Electron microscopy (EM) of the high intensity regions of the ethanol/CCl 4 treated liver sections revealed dramatic subcellular changes such as fragmentation of the granular endoplasmic reticulum (ER), formation of large vacuoles and lipid droplets in the cytoplasmic matrix and extensive swelling of the mitochondria as well as disruption of the cristae. Pretreatment with α-phenyl tert-butyl nitrone (PBN), a free radical spin trap, prior to halocarbon exposure, was found to reduce the CCl 4-mediated high intensity region in the liver images. Electron microscopy of the PBN pretreated CCl 4 exposed rat liver sections revealed only minor observable differences in subcellular organization, such as some swelling of the mitochondria, when compared to controls. In addition, these data suggest that ethanol may potentiate CCl 4 hepatotoxicity by increased formation of free radical intermediates. Inhibition of the CCl 4-induced edematous response in rat liver by PBN demonstrates that free radical intermediates, arising from the metabolism of CCl 4, are possibly the causal factor in the initiation of the edema.