A high glycemic index starch diet affects lipid storage-related enzymes in normal and to a lesser extent in diabetic rats

The of this study was to evaluate the chronic effects of a high (waxy corn) vs. a low (mung beans) glycemic index starch diet on the lipogenic enzymes, fatty acid synthase (FAS) and lipoprotein lipase (LPL). Normal and diabetic (streptozotocin-injected on d 2 of life) male Sprague-Dawley rats consumed a diet containing 575 g/kg carbohydrates either as waxy cornstarch (WCS) or as mung bean starch (MBS). After 3 wk, neither body weights nor relative epididymal fat pad weights differed. In diabetic rats, the WCS diet induced high basal plasma insulin levels. Plasma triglycerides were not significantly affected by diet in either normal or diabetic rats. Adipose tissue and liver LPL activities were not modified by the type of starch in the diet. In normal rats, FAS activity and gene expression in epididymal adipose tissue but not in liver were greater in rats consuming the WCS diet than in those consuming MBS. To evaluate the implication of insulin in this regulation, two genes regulated by insulin [GLUT4 and phosphoenolpyruvate carboxykinase (PEPCK)] were also studied. The high glycemic index WCS diet compared with the low glycemic index MBS diet resulted in lower hepatic PEPCK mRNA in both normal and diabetic rats. Normal, but not diabetic rats fed WCS had greater GLUT4 gene expression in adipocytes than did those fed MBS. We conclude that the total replacement of 575 g/kg low glycemic index starch by a high glycemic index starch for 3 wk caused the following in normal rats: 1) high FAS activity and mRNA in adipose tissue but not in liver and 2) high GLUT4 gene expression in adipose tissue. In both normal and diabetic rats this same diet resulted in lower hepatic PEPCK mRNA. Therefore, high glycemic index starch diet is implicated in stimulating FAS activity and lipogenesis and might have undesirable long-term metabolic effects.     

Reduction of hepatic phosphoenolpyruvate carboxykinase (PEPCK) activity by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is due to decreased mRNA levels

We have previously shown that the rate of hepatic gluconeogenesis is reduced in TCDD-treated rats and that this decrease in carbohydrate production is associated with a dose-dependent reduction of the activity of PEPCK, the rate limiting enzyme of gluconeogenesis. This derailment of glucose metabolism has been suggested to be the critical lesion in acute TCDD toxicity. To further elucidate the mechanism of decreased PEPCK activity we performed Northern blot analyses using a cDNA probe complementary to a portion of the mRNA coding for PEPCK. We have demonstrated that 4 and 8 days after TCDD treatment (125 micrograms/kg, p.o.) liver PEPCK mRNA in Sprague-Dawley rats was decreased to very low levels as compared to vehicle-treated and pair-fed control animals. This decline of PEPCK mRNA was paralleled by decreased levels of PEPCK protein, as revealed by Western blot analyses and was accompanied by a reduction in the enzymatic activity of PEPCK. These results indicate that the decrease of PEPCK activity by TCDD is most likely the result of decreased expression of the PEPCK gene. These together with previous results also suggest that many of the physiological responses occurring in TCDD-treated animals (reduced feed intake, decreased insulin, increased corticosterone, increased glucagon and cAMP levels) which would normally stimulate PEPCK gene expression, are ineffective. Furthermore tryptophan 2,3-dioxygenase (TdO) activity, which is regulated in a very similar fashion to PEPCK activity, is also reduced after TCDD treatment, suggesting a common mechanism by which TCDD alters the regulation of these enzymes. P-450 1A1 mRNA and related EROD activity were maximally induced under the conditions of these experiments and represent a positive control for TCDD-related alterations of gene expression. However, because of differences in the dose-response characteristics of TCDD-induced reduction of PEPCK activity and induction of EROD activity an involvement of the Ah receptor in the reduction of PEPCK activity cannot be postulated.     

Effects of exogenous hormones and glucose on plasma levels and hepatic metabolism of amino acids in the fetus and in the newborn rat

The present study examines the role of insulin, glucagon and cortisol in the regulation of gluconeogenesis from lactate and amino acids in fetal and newborn rats. Injection of glucagon in the full-term fetal rat caused a rise in glucose (and insulin) and a fall in blood levels of most individual amino acids, stimulated hepatic accumulation of 14C-amino isobutyric acid and 14C-cycloleucine and increased the conversion of 14C lactate, alanine and serine to glucose in vivo and in vitro (liver slices). Such changes were equivalent to the changes seen in 4 h old newborn rats. When glucagon was administered at birth, little difference was observed between control and treated animals in plasma amino acids and a smaller increment in conversion of 14C substrate to glucose occurred. By contrast, insulin injection at birth caused hypoglycemia, suppression of levels of certain amino acids and inhibition of conversion of 14C substrates into glucose. Glucose injection at birth caused elevated glycemia and plasma insulin and suppression of most amino acid levels and of conversion of 14C substrate into glucose. Cortisol injection at birth caused a marked, generalized by hyperaminoacidemia, a stimulation of glucagon secretion and of conversion of 14C substrates into glucose. These observations support the thesis that glucagon plays a major role in the induction of hepatic gluconeogenesis and that insulin acts as an antagonist hormone.     

Mechanisms of liver and muscle insulin resistance induced by chronic high-fat feeding

To elucidate cellular mechanisms of insulin resistance induced by excess dietary fat, we studied conscious chronically high-fat-fed (HFF) and control chow diet-fed rats during euglycemic-hyperinsulinemic (560 pmol/l plasma insulin) clamps. Compared with chow diet feeding, fat feeding significantly impaired insulin action (reduced whole body glucose disposal rate, reduced skeletal muscle glucose metabolism, and decreased insulin suppressibility of hepatic glucose production [HGP]). In HFF rats, hyperinsulinemia significantly suppressed circulating free fatty acids but not the intracellular availability of fatty acid in skeletal muscle (long chain fatty acyl-CoA esters remained at 230% above control levels). In HFF animals, acute blockade of beta-oxidation using etomoxir increased insulin-stimulated muscle glucose uptake, via a selective increase in the component directed to glycolysis, but did not reverse the defect in net glycogen synthesis or glycogen synthase. In clamp HFF animals, etomoxir did not significantly alter the reduced ability of insulin to suppress HGP, but induced substantial depletion of hepatic glycogen content. This implied that gluconeogenesis was reduced by inhibition of hepatic fatty acid oxidation and that an alternative mechanism was involved in the elevated HGP in HFF rats. Evidence was then obtained suggesting that this involves a reduction in hepatic glucokinase (GK) activity and an inability of insulin to acutely lower glucose-6-phosphatase (G-6-Pase) activity. Overall, a 76% increase in the activity ratio G-6-Pase/GK was observed, which would favor net hepatic glucose release and elevated HGP in HFF rats. Thus in the insulin-resistant HFF rat 1) acute hyperinsulinemia fails to quench elevated muscle and liver lipid availability, 2) elevated lipid oxidation opposes insulin stimulation of muscle glucose oxidation (perhaps via the glucose-fatty acid cycle) and suppression of hepatic gluconeogenesis, and 3) mechanisms of impaired insulin-stimulated glucose storage and HGP suppressibility are not dependent on concomitant lipid oxidation; in the case of HGP we provide evidence for pivotal involvement of G-6-Pase and GK in the regulation of HGP by insulin, independent of the glucose source.     

Posthemorrhagic antipyresis: what stage of fever genesis is affected?

This study was conducted to determine the time course of metabolic changes associated with a switch from a high-fat to a low-fat diet in rats. Adult rats, maintained on a high-fat diet (42% of energy from fat) for 4-5 weeks were switched to a low-fat diet (11% of energy from fat), and the activities of several liver enzymes were followed. Three different phases could be distinguished. The early phase, complete by 2 days after the switch in diets, included an increase in the activity of glucose 6-phosphate dehydrogenase (pentose phosphate pathway), an increase in pyruvate kinase and pyruvate dehydrogenase activities (terminal end of the glycolytic pathway) and an increase in ATP-citrate lyase and fatty acid synthetase (fatty acid synthesis pathway). The early phase also included a decrease in the activity of phosphoenolpyruvate carboxykinase (PEPCK, gluconeogenesis) and a lower branched-chain amino acid dehydrogenase activity (BCAADH, branched-chain amino acid degradation). The concentration of the allosteric phosphofructokinase regulator, fructose 2,6-bisphosphate (Fru-2,6-P2, glycolysis), decreased during the early phase. An intermediate phase could also be discerned between 3 and 10 days after the switch in diets. In this phase, the decreased Fru-2,6-P2 concentration and the decreased PEPCK and BCAADH activities observed in the early phase were reversed. The late phase occurred 10 days after the dietary switch and was characterized by an increase in the activities of glucokinase (glycolytic pathway) and glycogen phosphorylase (associated with glycogenolysis) and by a decrease in glutamate dehydrogenase, PEPCK and BCAADH activities. These measurements indicate that at least 20 days are required before metabolic changes associated with a switch in diet are complete.     

Effect of thyroxine on the NADH cytochrome c reductase activity of microsomes and outer mitochondrial membrane of rat liver depending on age

The rotenone-insensitive NADH-cytochrome c reductase activity and cytochrome b5 content in mitochondria and microsomes of liver of 1-, 3-, 12- and 24-month-old rats were studied. Thyroxine injection caused a considerable decrease in the microsomal activity in all age groups under study; in mitochondria this effect was increased with age. The decrease of the cytochrome b5 content was maximal in the microsomes and mitochondria of 12- and 24-month-old animals and was insignificant in 1-month-old rats. It was assumed that the age variations in regulation of the outer mitochondrial membrane function can be due changes in their population.     

Specific inhibition of hepatic fatty acid synthesis exerted by dietary linoleate and linolenate in essential fatty acid adequate rats

Dietary linoleate and linolenate were investigated for their ability to specifically inhibit liver and adipose tissue lipogenesis in meal-fed (access to food 900-1,200 hr), essential fatty acid (EFA) adequate rats. Supplementing a high carbohydrate diet containing 2.5% safflower oil with 3% palmitate 16:0, oleate 18:1, or linoleate 18:2 did not affect in vivo liver or adipose tissue fatty acid synthesis. However, 18:2 addition to the basal diet did result in a significant (P less than 0.05) decline of liver fatty acid synthetase (FAS) and glucose-6-phosphate dehydrogenase (G6PD) activities. When the safflower oil content of the basal diet was reduced to 1%, the addition of 3% 18:2 or linolenate 18:3 significantly (P less than 0.05) depressed hepatic FAS, G6PD, and in vivo fatty acid synthesis by 50%. Addition of 18:1 caused no depression in hepatic FAS activity but did result in a significant (P less than 0.05) decline in liver G6PD activity and fatty acid synthesis which was intermediate between basal and basal +18:2- or +18:3-fed animals. Adipose tissue rates of lipogenesis were completely unaffected by dietary fatty acid supplementation. Similarly, the addition of 3 or 5% 18:3 to a basal diet for only one meal resulted in no change in lipogenesis relative to that in animals fed the basal diet. The data indicate that, like rats fed EFA-deficient diets, dietary 18:2 and 18:3 exert a specific capacity to depress rat liver FAS and G6PD activities and rate of fatty acid synthesis.     

The effect of prednisolone and a protein-deficient diet on plasma albumin and fibrinogen in a turpentine-induced acute-phase reaction in rats

The acute-phase reaction (APR) that follows inflammation is characterized by profound metabolic changes such as hypoalbuminemia, which is frequently aggravated by malnutrition; and hyperfibrinogenemia. Because some of these changes are mediated by cytokines, corticosteroids that are known to suppress cytokine production might be expected to alleviate the course of the APR. In the present study, for 3 weeks rats were fed (1) a standard diet (25%) protein), (2) a protein-deficient diet (5% protein), or (3) a standard diet supplemented by treatment with intraperitoneal prednisolone (7.5 mg twice daily starting 3 days before and throughout the experiment). Changes in plasma albumin, fibrinogen, and total protein levels were measured 0, 1, 3, and 8 days after turpentine was injected subcutaneously. Albumin and fibrinogen were immunohistochemically stained in the liver 0, 3, and 8 days after injection. Plasma albumin decreased by roughly 50% in all three groups, and reached a nadir on day 3. Fibrinogen peaked by day 1 in all animals and fell gradually thereafter. The total protein concentration, which was higher with prednisolone, remained unchanged in all three groups. The level of immunostainable liver albumin was initially reduced in malnourished rats. If further diminished in the majority of hepatocytes after administration of turpentine in all groups. Although few hepatocytes stained positive for fibrinogen before the onset of inflammation, uniform increase in immunostaining occurred by day 3 in all rats regardless of treatment. Neither prednisolone nor malnutrition substantially altered the decrease in plasma albumin and the simultaneous increase in fibrinogen in a turpentine-induced APR.(ABSTRACT TRUNCATED AT 250 WORDS)     

Caloric restriction reverses hepatic insulin resistance in aging rats by decreasing visceral fat

Hyperinsulinemia and increased visceral/abdominal fat (VF) are common features of human aging. To examine the relationships among VF, peripheral, and hepatic insulin sensitivity, we studied 4- and 18-mo-old male Sprague-Dawley rats (n = 42) fed ad libitum (4 AL and 18 AL) or moderately calorie restricted (18 CR) up to 18 mo of age. Total fat mass (FM) and VF were decreased in 18 CR to approximately one-third of that of 18 AL (P < 0.001), while lean body mass (LBM) was unchanged. Most important, 18 CR had more FM (65+/-6 vs. 45+/-6 g) but less VF (7.8+/-0.6 vs. 12.3+/-3.3 g) compared with 4 AL (P < 0.01 for both). Thus, the effects of variable VF on HIS could be assessed, independent of FM and age. Marked hepatic insulin resistance ensued with aging (18 AL) and CR restored hepatic insulin sensitivity to the levels of young rats, while peripheral insulin sensitivity remained unchanged (by insulin clamp of 18 mU/kg/min). In fact, the rates of insulin infusion required to maintain basal hepatic glucose production in the presence of pancreatic clamp were 0.75+/-0.10, 1.41+/-0.13, and 0.51+/-0.12 mU/kg . min, in 4 AL, 18 AL, and 18 CR, respectively (P < 0.01 between all groups), and in 18 CR rats infused with insulin at similar rates as in the 18 AL (1.4 mU/kg/min) hepatic glucose production was decreased by 32% (P < 0. 005). Furthermore, when 18 CR rats were fed AL for 14 d, VF rapidly and selectively increased and severe hepatic insulin resistance was induced. We propose that in this animal model the age-associated decrease in hepatic (rather than peripheral) insulin action is the major determinant of fasting hyperinsulinemia and that increased visceral adiposity plays the major role in inducing hepatic insulin resistance. Thus, interventions designed to prevent the accumulation of VF are likely to represent an effective mean to improve carbohydrate metabolism in aging.     

Some peculiarities of the glucoregulatory response to glucose infusion in the rat

The glucoregulatory response to the i.v. infusion of different doses of glucose and glucose plus insulin was studied in anesthetized rats by using the primed constant infusion of glucose-2-3H. Infusion of glucose at the rate of 10 mg/kg/min induced a rise of about 100% in blood glucose, while the hepatic release of glucose showed only a small and transient decrease. A proportional increase of glycemia and glucose utilization (Rd) was observed without any appreciable change in the metabolic clearance rate (MCR) of glucose; a two-fold increase in plasma insulin was recorded at all times. In the group of rats receiving 20 mg/kg/min of glucose, changes in the above parameters were slightly greater; MCR showed a moderate increment in spite of the six-fold rise of plasma insulin. Finally, the influsion of large doses of insulin together with 20 mg/kg/min of glucose resulted in complete cessation of glucose release by the liver and in a remarkable increase of Rd and MCR. These results suggest a poor adaptability of the glucoregulatory system of the rat in response to glucose infusion as compared to other mammalian species.     

Effects of chronic administration of benfluorex on the pharmacokinetics of iodine 123 labelled insulin in Zucker obese rats (fa/fa)]

Zucker obese rats (fa/fa), aged 8 to 10 weeks, were treated orally by benfluorex (2 x 25 mg.kg-1, day-1) for 2 weeks and were compared with a control group of the same age treated with placebo. Benfluorex induced a break in the weight curve, a significant fall in serum triglycerides, blood glucose and plasma insulin and in the insulin content of the pancreas. Following intrajugular injection of iodine 123 labelled insulin, the liver of the treated animals bound 25 percent more insulin than the liver of control animals. Conversely, the renal clearance of insulin of the treated animals was reduced in comparison to the placebo group. These studies confirm that, in an animal model of obesity associated with insulin resistance, benfluorex exerts a marked hypolipidemic effect and improves insulin resistance. They also demonstrate an increased targeting of insulin towards hepatic receptors either due to an increase in the hepatic blood flow or to an increase in the number of hepatic receptors or to an increase in the affinity of these receptors. However, speculative considerations make this last mechanistic hypothesis somewhat improbable.     

Time courses of hepatic injuries induced by chloroform and by carbon tetrachloride: comparison of biochemical and histopathological changes

The relationship was investigated between biochemical and morphological changes in chloroform (CHCl3)- and carbon tetrachloride (CCl4)-induced liver damage. The time courses of hepatic microsomal cytochrome P450 (CYP) content, hepatic microsomal CYP2E1 activity, hepatic reduced glutathione (GSH) content, plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were examined in relation to the liver morphology in rats orally treated with CHCl3 or CCl4 (3.35 mmol/kg). The CYP content and the activity of CYP2E1 markedly decreased in the CCl4-treated rats 3 h after treatment compared to much lower decreases in the CHCl3-treated rats. The hepatic GSH content was decreased to a similar extent in both groups of rats at 3 h after treatment; in the CCl4-treated rats, the GSH content continued to decrease, reaching a minimum at 24 h and without attaining the normal level at 72 h after treatment. By contrast, hepatic GSH content in the CHCl3-treated rats began to increase from 6 h, attaining complete recovery 48 h after treatment. Plasma ALT and AST activities were significantly elevated by CCl4 as early as 3 h after treatment, while the activities in the CHCl3-treated rats did not increase until 6 h after treatment. In both groups of rats, ALT and AST activities reached a maximum at 24 h, and gradually decreased, remaining at abnormal levels at 72 h. Hepatic cells in the CCl4-treated rats were found to be necrotic as early as 3 h post-treatment, whereas few or no morphological changes appeared in the liver of CHCl3-treated rats. The extent of necrosis was at a maximum 24 h after treatment in both CHCl3- and CCl4-treated rats. In addition, some necrotic cells remained in the liver of CCl4-treated rats 72 h after treatment, while the necrosis in the CHCl3-treated rats was almost negligible. The present results indicate that almost the same time-courses of biochemical and morphological changes were followed in rats of both the CHCl3- and CCl4-treated groups.     

Short-term handling of the slimming agent oleoyl-estrone in liposomes (Merlin-2) by the rat

Female adult rats were injected in the jugular vein with oleoyl-3H-estrone incorporated into liposomes. The label rapidly disappeared from the blood, being taken up by the tissues, mainly liver, spleen and lung, which filtered most of the label. However, many other tissues, such as the heart, brown adipose tissue, adrenals and visceral fat incorporated significant amounts of oleoyl-estrone. The analysis of the form in which the label remained 10 min after the injection showed that it was hydrolysed in a large proportion even in liver and lungs. However, in most tissues (brain, brown and white - periovaric - adipose tissues and ovaries), intact oleoyl-estrone accounted for less than one quarter of all tissue label, and less than 10% in the case of subcutaneous adipose tissue and uterus. This rapid destruction of oleoyl-estrone is in agreement with the active role of this compound in the control of body weight.     

Effect of aging on insulin receptor, insulin receptor substrate-1, and phosphatidylinositol 3-kinase in liver and muscle of rats

Insulin stimulates the tyrosine kinase activity of its receptor, resulting in the phosphorylation of its cytosolic substrate, insulin receptor substrate-1 (IRS-1), which, in turn, associates with phosphatidylinositol 3-kinase (PI 3-kinase), thereby activating the latter. Aging is associated with insulin resistance, but the exact molecular mechanism is unknown. In the present study, we examined the levels and phosphorylation status of the insulin receptor and IRS-1 as well as the association between IRS-1 and PI 3-kinase in the liver and muscle of 2-, 5-, 12-, and 20-month-old rats. There were no changes in the insulin receptor concentration in the liver and muscle of rats 2-. 5-, 12-, and 20-month rats. There were no changes in the insulin receptor concentration in the liver and muscle of rats 2-20 months old, as determined by immunoblotting using antibody to the COOH-terminus of the receptor. However, insulin stimulation of receptor autophosphorylation, as determined by immunoblotting with antiphosphotyrosine antibody was reduced by 25% (P < 0.05) in the liver and muscle of rats at 20 months. Interestingly, IRS-1 protein levels decrease at an early stage (5 months) by 58 +/- 9%, (P < 0.01) and remained at low levels thereafter in muscle, but not in liver. In samples previously immunoprecipitated with anti-IRS-1 antibody and blotted with antiphosphotyrosine antibody, there were 60 +/- 9% (P < 0.001) and 92 +/- 4% (P < 0.001) decreases in the insulin-stimulated IRS-1 association with PI 3-kinase was decreased by 70 +/- 2% in the liver and muscle, respectively, of 20-month rats. The insulin-stimulated IRS-1 association with PI 3-kinase was decreased by 70 +/- 2% in the liver (P < 0.001) and by 98 +/- 3% (P < 0.001) in the muscle of 20-month-old rats, with no change in the PI 3-kinase protein levels. The phosphotyrosine-associated PI 3-kinase activity after insulin stimulation was dramatically reduced in liver and muscle of 20-month-old rats compared to that in 2-month-old rats. Finally, by immunoprecipitation, the detection of insulin-stimulated IRS-2 phosphorylation followed the same pattern as that for IRS-1 in both liver of 2- and 20-month-old rats. These data suggest that changes in the early steps of insulin signal transduction may have an important role in the insulin resistance observed in old animals.     

Abdominal hysterectomy practice patterns in the United States

Diets rich in polyunsaturated fatty acids (PUFA) are well known to suppress hepatic lipogenic enzymes compared to fat-free diets or diets rich in saturated fatty acids. However, the mechanism underlying suppression of lipogenic enzymes is not quite clear. The present study was undertaken to investigate whether lipid peroxidation products are involved in suppression of lipogenic enzymes. Therefore, an experiment with growing male rats assigned to six groups over a period of 40 d was carried out. Rats received semisynthetic diets containing 9.5% coconut oil and 0.5% fresh soybean oil (coconut oil diet, peroxide value 5.1 meq O2/kg oil), 10% fresh soybean oil (fresh soybean oil diet, peroxide value 9.5 meq O2/kg oil), or 10% thermally treated soybean oil (oxidized soybean oil diet, peroxide value 74 meq O2/kg oil). To modify the antioxidant state of the rats, we varied the vitamin E supply (11 and 511 mg alpha-tocopherol equivalents per kg of diet) according to a bi-factorial design. Food intake and body weight gain were not influenced by dietary fat and vitamin E supply. Activities of hepatic lipogenic enzymes were markedly influenced by the dietary fat. Feeding either fresh or oxidized soybean oil diets markedly reduced activities of fatty acid synthase, (FAS), acetyl CoA-carboxylase, (AcCX), glucose-6-phosphate dehydrogenase, (G6PDH), 6-phosphogluconate dehydrogenase, and ATP citrate lyase (ACL) relative to feeding the coconut oil diet. Moreover, feeding oxidized soybean oil slightly, but significantly, lowered activities of FAS, AcCX, and ACL compared to feeding fresh soybean oil. Activities of hepatic lipogenic enzymes were reflected by concentrations of triglycerides in liver and plasma. Rats fed the coconut oil diet had markedly higher triglyceride concentrations in liver and plasma than rats consuming fresh or oxidized soybean oil diets, and rats fed oxidized soybean oil had lower concentrations than rats fed fresh soybean oil. The vitamin E supply of the rats markedly influenced concentrations of thiobarbituric acid-reactive substances in liver, but it did not influence activities of hepatic lipogenic enzymes. Because the vitamin E supply had no effect, and ingestion of an oxidized oil had only a minor effect, on activities of hepatic lipogenic enzymes, it is strongly suggested that neither exogenous nor endogenous lipid peroxidation products play a significant role in the suppression of hepatic lipogenic enzymes by diets rich in PUFA. Therefore, we assumed that dietary PUFA themselves are involved in regulation of hepatic lipogenic enzymes. Nevertheless, the study shows that ingestion of oxidized oils, regardless of the vitamin E supply, also affects hepatic lipogenesis, and hence influences triglyceride levels in liver and plasma.     

Sinusoidal endothelial cell damage by activated macrophages in rat liver necrosis

BACKGROUND: Massive hepatic necrosis caused by fibrin deposition in the hepatic sinusoids develops with hepatic macrophage activation in rats given endotoxin after administration of heat-killed Corynebacterium parvum. Targeted cells of such macrophages were investigated. METHODS: In C. parvum-treated rats, the pathological appearance of liver cells was serially measured in serum following endotoxin administration and compared with the appearance in the perfusate during closed liver perfusion with endotoxin. RESULTS: Serum activities of tumor necrosis factor, purine nucleoside phosphorylase present in both hepatocytes and sinusoidal endothelial cells, and levels of alanine aminotransferase were higher after 30 minutes, 1 hour, and 3 hours, respectively. Pretreatment of rats with gadolinium chloride, an inhibitor of macrophage function, reduced this liver injury. Although alanine aminotransferase activity remained almost unchanged in the liver perfusate, purine nucleoside phosphorylase activity increased. This increase was reduced when rats were pretreated with gadolinium chloride. There was sinusoidal endothelial cell damage around hepatic macrophages in the liver perfused with endotoxin. CONCLUSIONS: Activated hepatic macrophages may cause sinusoidal endothelial cell damage leading to hepatocyte necrosis in rats given C. parvum and endotoxin.