Severe hepatic steatosis and focal necrosis of hepatocytes have previously been induced in rats by continuous intragastric infusion of ethanol and a diet containing only 5% fat as a per cent of total calories as reported by us previously. Since the ethanol diet fed ad libitum with such a low level of fat has previously failed to produce alcoholic fatty liver, continuously high blood alcohol levels achieved in this model appeared to be key in induction of the progressive pathologic lesions in the liver. In the current study, effects of increased fat intake on alcohol-induced liver injury were investigated. Seventeen pairs of male Wistar rats were implanted with gastrostomy cannulas and infused with a liquid diet containing 25% of total calories as fat plus ethanol or isocaloric dextrose. Ethanol intake was progressively increased from 32% up to 47% of total calories to maintain sustained intoxication for 30 to 120 days. Light and electron microscopic examination of the liver revealed moderate to severe fatty infiltration in all of the ethanol-fed rats, of which 14 had spotty or zonal necrosis in the centrilobular areas accompanied by polymorphonuclear and mononuclear cell infiltration. In addition, fibrosis was observed in association with the necrotic lesions or with large-droplet steatosis. Reticulin and trichrome stains clearly demonstrated fine fibrosis, including perivenular fibrosis as well as septum formation progressing to bridging fibrosis. Furthermore, increased numbers of Ito cells and myofibroblasts were observed in the perivenular fibrotic areas. These results demonstrate striking potentiation of alcohol-induced liver injury by the increased fat intake or by the concomitant decrease in carbohydrate intake.(ABSTRACT TRUNCATED AT 250 WORDS)