Activation of mitogen activated protein kinase (MAPK) during D-galactosamine intoxication in the rat liver

A significant increase in plasma glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase was observed 6 h after intraperitoneal administration of D-galactosamine (D-Galn). Three hours after administration of D-Galn, the vitamin C concentration in the liver decreased significantly compared to that in a control group and thereafter the hepatic vitamin C concentration remained at a significantly lower level. Phosphorylated JNK (c-Jun NH2-terminal kinase) and phosphorylated ERK (extracellular signal-regulated kinase) started increasing 3 h after D-Galn treatment and remained at a high level for 6-12 h after the treatment, while phosphorylated p38 MAPK increased significantly 6 h after D-Galn administration. These results indicated that oxidative stress and the activation of JNK and ERK took place almost simultaneously, followed by the activation of p38 MAPK.

Connexin 32 dominant-negative mutant transgenic rats are resistant to hepatic damage by chemicals

Connexins are subunits of gap junction channels, which allow direct transfer of ions, secondary messenger molecules, and other metabolites between contacting cells. Gap junctions are believed to be involved in tissue homeostasis, embryonic development, and control of cell proliferation. Several studies have shown that cell damage signals are transmitted through gap junctions when cells are irradiated or when cells bearing the herpes simplex virus-thymidine kinase (HSV-TK) gene are treated with ganciclovir. We established 2 lines of transgenic rats with a dominant-negative mutant of connexin 32 gene under control of the albumin promoter. In the livers of transgenic rats, membrane localization of normal endogenous connexin 32 protein is disturbed, and gap junction capacity measured by scrape dye-transfer assay in vivo is markedly decreased when compared with wild-type rats. The present investigation concerned susceptibility to the liver-toxic substances D-galactosamine and carbon tetrachloride. These toxicants induced massive liver cell death and elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the wild-type rats; however, much fewer liver cells were damaged and serum enzyme elevation was much lower in the transgenic rats. In conclusion, gap junctional intercellular communication (GJIC) plays an important role in toxic effects of chemicals; damage or death signals may pass through gap junctions in the rat liver in vivo.

Ameliorative effect of an urinary preparation on acetaminophen and D-galactosamine induced hepatotoxicity in rats

The effect of oral administration of a preparation of human urine (PHU) on acute liver injury was examined in rats intoxicated with acetaminophen and D-galactosamine. The results indicated that PHU protected the liver from acetaminophen and D-galactosamine-induced injury as judged by morphological and biochemical observation. An increase in lipid peroxide concentrations and decrease in protein concentrations occurred in the liver by D-galactosamine injection, PHU administration significantly prevented these changes.

Glycine and uridine prevent D-galactosamine hepatotoxicity in the rat: role of Kupffer cells

Extrahepatic factors, such as increased gut permeability and bacteria from the gut, have been shown to play a role in D-galactosamine toxicity in rats. Because bacterial endotoxin activates Kupffer cells, the purpose of this study was to clarify the role of Kupffer cells in the mechanism of D-galactosamine hepatotoxicity in rats and determine whether uridine, a compound that rescues animals from D-galactosamine toxicity, affects Kupffer cells. Rats were fed control or glycine (5%) containing diets to prevent Kupffer cell activation or treated with gadolinium chloride (GdCl3, 20 mg/kg) to destroy Kupffer cells selectively before injection of D-galactosamine (500 mg/kg, intraperitoneally). D-galactosamine caused panlobular focal hepatocellular necrosis, polymorphonuclear cell infiltration, and increased serum transaminases significantly at 24 hours. Dietary glycine or pretreatment with GdCl3 prevented these effects. D-galactosamine caused a transient increase in circulating endotoxin that was maximal at 1 hour and was blunted significantly by dietary glycine. Additionally, antisera to tumor necrosis factor-alpha (TNF-alpha) prevented hepatotoxicity caused by D-galactosamine. Moreover, apoptosis in hepatocytes caused by D-galactosamine occurred before necrosis (6 hours) and was prevented by glycine, GdCl3, TNF-alpha antiserum, and uridine. Thus, it was hypothesized that TNF-alpha from Kupffer cells causes apoptosis after D-galactosamine administration in the rat. Indeed, increases in TNF-alpha messenger RNA (mRNA) were detected as early as 2.5 hours after D-galactosamine treatment. Previous work proposed that uridine blocks D-galactosamine toxicity by preventing inhibition of mRNA synthesis. In view of these results, the possibility that uridine might affect Kupffer cells was investigated. Uridine significantly blunted the increase in [Ca2+]i and release of TNF-alpha caused by endotoxin in isolated Kupffer cells and prevented apoptosis caused by D-galactosamine treatment in vivo. These data support the hypothesis that uridine prevents D-galactosamine hepatotoxicity not only by rescuing the hepatocyte in the late phases of the injury but also preventing TNF-alpha release from Kupffer cells thereby blocking apoptosis that occurs early after D-galactosamine treatment. Taken together, these data strongly support the role of Kupffer cell activation by endotoxin early after D-galactosamine treatment as an important event in the mechanism of hepatotoxicity in the rat.

Glutathione modulates rat and mouse hepatocyte sensitivity to tumor necrosis factor toxicity

BACKGROUND & AIMS

Tumor necrosis factor (TNF)-alpha causes much of the hepatocellular injury and cell death that follows toxin-induced liver damage. The mechanism by which toxic liver injury sensitizes hepatocytes to TNF-alpha cytotoxicity is unknown. The aim of this study was to determine the role of the antioxidant glutathione in this process.

METHODS

A rat hepatocyte cell line and primary hepatocytes sensitized to TNF-alpha toxicity by the addition of actinomycin D were examined for changes in glutathione levels and for the effects of glutathione depletion or supplementation on cell death. The in vivo effects of glutathione depletion were determined in mice treated with galactosamine plus lipopolysaccharide.

RESULTS

Treatment of hepatocytes with actinomycin D and TNF-alpha induced apoptotic cell death without affecting cellular glutathione levels or production of the reactive oxygen intermediate H2O2. Glutathione depletion induced by diethyl maleic acid significantly increased TNF-alpha-induced cell death even when this agent was administered 2 hours after TNF-alpha treatment. Hepatocyte cell death was not affected by glutathione supplementation. In mice treated with galactosamine plus lipopolysaccharide, glutathione depletion increased mortality from liver injury from 32% to 72%.

CONCLUSIONS

TNF-alpha-induced cytotoxicity in hepatocytes occurs in the absence of glutathione depletion. However, a preexisting reduction in glutathione levels can significantly increase cell death from TNF-alpha.

Effect of 4-phenyl-1,3-dithia-2-thioxo-cyclopent-4-ene on liver injury induced by repeated exposure to galactosamine plus carbon tetrachloride in rats

The protective effects of 1,3-dithia-2-thioxo-cyclopent-4-ene (DT827A),4-phenyl-1,3-dithia-2-thioxo-cyclopent- 4-ene (DT827B) and 4-(4-fluorophenyl)-1,3-dithia-2-thioxo-cyclopent-4-ene (DT827C) on liver injury induced by D-galactosamine plus carbon tetrachloride (D-GalN + CCl4) and that of DT827B on liver injury induced by thioacetamide were studied using male rats. Out of the three DT827 series of compounds, DT827B was more effective on liver injury induced by the combination exposure to D-GalN + CCl4 for 4 weeks, and accordingly the following two experiments were carried out using DT827B only. Twelve-week administration of DT827B at dose levels of 5, 10 and 20 mg/kg/day revealed a therapeutic effect against liver injury induced by D-GalN + CCl4 dose-dependently, and another twelve-week administration of DT827B at the same three dose levels also revealed a therapeutic effect against liver injury induced by thioacetamide dose-dependently. A hepatoprotective potential of DT827B was suggested under the conditions of these studies.

[The effect of Essentiale and riboxin on the immunomodulating properties of the erythrocytes in a toxic liver lesion]

D-galactosamine (DGA) increases the erythrocyte content of malonic dialdehyde (MDA) and the degree of peroxide hemolysis (DPH) of the erythrocytes, and reduces the 2,3-diphosphoglycerate (DPG) and ATP content. DGA induces the appearance of immunosuppressive properties in light erythrocytes. Essentiale (2 mg/kg) reduces the MDA content and DPH in the heavy erythrocytes and induces the appearance of immunostimulating properties in them. Riboxine (2 mg/kg) reduces the content of DPG and ATP in the light erythrocytes and prevents the appearance of immunosuppressive properties in them. Injection of 2 mg/kg of Essentiale or riboxine does not affect the development of the immune response induced by sheep erythrocytes in DGA poisoned rats. Combined injection of the compounds in a dose of 1 mg/kg intensifies the immune response of the poisoned animals.

[Lidocaine as an immunomodulator in a toxic liver lesion]

D-galactosamine (DGA) increases the malonic dialdehyde (MDA) content in the erythrocytes, reduces the ATP content, and induces the appearance of immunosuppressive properties in the red cells. Administration of lidocaine attenuates or completely removes these effects of DGA in poisoned animals. Extracorporeal treatment of the erythrocytes of intact rats with blood serum of DGA-poisoned reduces the ATP content and induces the appearance of immunosuppressive properties in the erythrocytes. Blood serum of DGA-poisoned rats which had been given lidocaine does not cause such effects.

Fructose 1,6-bisphosphate protects against D-galactosamine toxicity in isolated rat hepatocytes

Incubation of hepatocytes with D-galactosamine (GalN) produced a dose-dependent alteration in cell viability and a fall in ATP and fructose 2,6-bisphosphate (Fru-2,6-P2) levels. The reduction in Fru-2,6-P2 can be explained by changes in the substrates or modulators of 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase, because neither the adenosine 3',5'-cyclic monophosphate level nor the activity ratio of the enzyme was modified. Microcalorimetric measurements showed that GalN produced an exothermic peak followed by a progressive decrease in heat dissipation. Simultaneous administration of GalN and fructose 1,6-bisphosphate (Fru-1,6-P2) significantly increased cell viability, and concentrations of ATP and Fru-2,6-P2 and led to stable heat production. In the presence of Fru-1,6-P2 alone, hepatocytes kept ATP and Fru-2,6-P2 levels constant, whereas they increased the oxygen uptake-to-heat output ratio. Our results suggest that GalN initiates the hepatotoxic effect by means of an energy-dissipating interaction, produced before its metabolism and presumably at the membrane level, whereas Fru-1,6-P2 protects the cells against this injury in a way that prevents the initial interaction and increases the metabolic efficiency of the cell.

Protective action of putrescine against rat liver injury

The hepatoprotective action of orally dosed putrescine was investigated using rat models of liver injury. When rats received putrescine orally soon after a dose of carbon tetrachloride or D-galactosamine, deranged serum alanine aminotransferase values and prothrombin times were significantly attenuated compared with control levels, with improved histologic extent of liver injury. Putrescine addition to the medium of rat hepatocytes in primary culture reduced cell killing induced by D-galactosamine or the membrane detergents chenodeoxycholic acid and Triton X-100. Similar reduction was seen in cells exposed to tert-butyl hydroperoxide (TBHP), an agent producing cell death through lipid peroxidation, with attenuation of cellular malondialdehyde content. Putrescine also significantly attenuated the extent of increased plasma membrane microviscosity as assessed with 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene in TBHP-treated cells. These results suggest that orally given putrescine protects against liver injury. Plasma membrane stabilization and reduction of lipid peroxidation may contribute to this hepatoprotection.

Hepatic D-galactosamine toxicity studied with localized in vivo 31P magnetic resonance spectroscopy in intact rats

Spatially resolved 31P magnetic resonance spectroscopy (MRS) at 4.7 T was applied to noninvasively assess liver phosphorus metabolites in a biochemically well-characterized model of hepatotoxicity induced by injection of a sublethal dose of D-galactosamine (galN). A newly developed hybrid method based on spectral localization with B0 and B1 gradients was employed to obtain multivoxel spectra in intact anesthesized rats. Spatially localized in vivo spectra were recorded 0 to 26 h after galN injection of female rats. In response to galN exposure, diphosphodiester peaks ascribed to UDP-hexosamines became detectable by 4 h and persisted up to 26 h. A metabolite coresonating with inorganic phosphate increased rapidly in intensity by 2 h after galN and returned to baseline by 18 h; this resonance was shown not to be Pi and was assigned to galN-1-phosphate by subsequent high resolution MRS experiments on extracts prepared from these livers. These results confirmed in vivo the metabolic perturbations described previously for this model of hepatotoxicity following biochemical studies based on classical extraction methods. Unlike the in vitro studies, however, these noninvasive experiments provided additional information on the time course of metabolic alterations on the same animal.

Bioartificial liver using hepatocytes on biosilon microcarriers: treatment of chemically induced acute hepatic failure in rats

An artificial liver support procedure based on hemoperfusion via hepatocytes cultured on microcarriers is described. The efficiency of the system was assessed by the survival rate of rats treated with either lethal dosage of 7% CCl4 [30 ml/kg body weight (b.w.)] or D-galactosamine (2.5 g/kg b.w.). In CCl4-treated rats, hemoperfusion via empty microcarriers (n = 16) revealed no surviving animals, whereas the use of the bioartificial liver (n = 11) resulted in 80% (p less than 0.01) and 60% (p less than 0.05) survival 48 and 168 h after hepatotoxin, respectively. For the same time periods, the survival rate in D-galactosamine-intoxicated rats after hemoperfusion with hepatocytes (n = 20) was approximately 60% (p less than 0.05) and was only 5% in those of rats treated with empty microcarriers (n = 20). Sublethal dosage of 7% CCl4 (15 ml/kg b.w.) caused 25% mortality and prolonged (48 h) increase of activity of the liver enzymes and bilirubin levels in the serum of surviving animals. In these rats (n = 8) at the end of 3 h of hemoperfusion via hepatocytes, the bilirubin concentration decreased by 45% as compared with the control group (n = 6) treated with empty microcarriers. Moreover, by 48 h after intoxication, the use of the bioartificial liver resulted in more than a three-fold decrease in glutamate-oxaloacetate transaminase and a 10-fold decrease in glutamate-pyruvate transaminase serum activity as well as a fivefold decline in total and a ninefold decline in conjugated bilirubin levels as compared with the control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

[The correction with hepatic protectors of structural metabolic disorders in the liver in D-galactosamine poisoning]

The hepatoprotective agents silybinin, essentiale and eplir (the complex of phospholipids and caratinoids from the mud) prevent in D-galactosamine-induced intoxication of rats the development of hepatitis, hepatocyte necrosis, a decrease in hepatocytes of the activity of the enzymes of mitochondria and endoplasmic reticulum, labilization of lysosomes. These drugs stimulate D-galactosamine-suppressed antitoxic function of the liver: they increase the contents of RNA, cytochromes P-450, b5, the activity of amidopyrine-D-demethylase, hydroxylases of hexobarbital and aniline, improve the activity of the respiratory chain of microsomes, counteract inactivation of cytochrome P-450 into cytochrome P-420. Essentiale and eplir activate conjugation of xenobiotics with reduced glutathione.

[The antitoxic function of the liver in D-galactosamine poisoning]

Two intragastric administrations of 500 mg/kg of D-galactosamine reduce the RNA and the cytochrome P-45, and b5 content in the hepatic microsomes of rats; inhibit the activity of aminopyrine-N-demethylase, hexobarbital hydroxylase, aniline-p-hydroxylase, and glutathione-S-transferase; reduce the rate of NADP.H and NAD.H oxidation; accelerate inactivation of cytochrome P-450 to cytochrome P-420; reduce the number of points of hexobarbital binding with N-octilamine, though increase the hemoprotein affinity to these substrates. Destruction of the nucleus, endoplasmic reticulum, and mitochondria occurs in the hepatocytes of D-galactosamine poisoned rats.

Decrease in the number of receptors for epidermal growth factor in the liver of D-galactosamine-intoxicated rats

Hepatic transport of epidermal growth factor (EGF) was studied in D-galactosamine-intoxicated rats by the multiple-indicator dilution (MID) method. The extraction ratio of 125I-labeled EGF in the intoxicated rats, obtained from a model-independent analysis of the dilution curves, decreased to 45% of the control values. A distributed two-compartment model was fitted to the dilution data by nonlinear least-squares regression, and the kinetic parameters, kon.PT (product of on-rate constant and receptor density), koff (off-rate constant) and ks (sequestration rate constant) were determined. The values of kon.PT and ks in the intoxicated rats decreased to approximately one-half and one-third of those in the control rats respectively. Similar decreases in the kon.PT and ks values in the intoxicated rats were also observed for the transport of 125I-labeled insulin, a positive control, into the liver. The 125I-labeled EGF binding experiment at equilibrium using liver homogenates revealed that the intoxication reduced the receptor density (PT) to one-third of the control values, whereas the equilibrium dissociation constant (kd) did not change significantly. The activities of Na+,K+-ATPase, cytochrome P-450 and glutathione S-transferase decreased in the intoxicated rats to 70-80% of the control values. The number of nuclei per unit area of tissue slices was also reduced to 70% of the control. Thus, the extent to which the enzyme activities and the number of nuclei decreased in the intoxicated liver was smaller than that of the number of EGF receptors. It is concluded that the reduction of EGF receptors cannot be explained by the "intact hepatocyte hypothesis" but rather by the functional change of hepatocytes induced by the administration of D-galactosamine.

[Morphological changes in the liver in acute galactosamine poisoning with different protein levels in the diet]

Changes in hepatocyte ultrastructure after galactosamine administration to rats adapted to diets with different protein content have been studied. Typical galactosamine effects on hepatocytes were manifested earlier in animals on low and high protein diets. At the same time a considerable decrease in protein synthesis led to insufficient expression of the reparative processes in all the observed groups of animals.

Protective effect of malotilate against galactosamine intoxication in the rat

The influence of malotilate was tested in a model of galactosamine (GalN) intoxication in the rat; two different experiments were carried out: (1) an acute intoxication (GalN at a single dose of 500 mg/kg s.c.): after pretreatment with malotilate (100 and 200 mg/kg p.o.) a marked reduction of hepatocellular injury, as shown by decrease of ASAT, ALAT and GlDH, was observed; (2) a subacute intoxication, GalN at 3 x 300 mg/kg s.c. for 3 consecutive days, which induced a more moderate hepatic necrosis: malotilate, 200 mg/kg/day p.o. for 4 days beginning the day before the first GalN injection, decreased significantly the disturbances of the biochemical measured parameters (plasma total proteins, prothrombin time, fibrinogen level, BSP clearance and hepatic total lipids) and accelerates the return to normal. Pathology studies revealed that pretreatment with malotilate increased markedly the number of mitoses observed in the hepatic cells after intoxication. In addition, the time of appearance of these mitoses was earlier in malotilate treated animals. From these studies, it can be concluded that malotilate protects against hepatocellular injury induced by GalN in the rat and that it stimulates the regenerative capacity of the liver after intoxication.

Hepatic cysteamine and non-protein sulfhydryl levels following cystamine or cysteamine treatment of galactosamine-poisoned rats

Hepatic cysteamine and non-protein sulfhydryl (NPSH) levels were determined in galactosamine (GAL)-poisoned rats following hepatoprotective cystamine or cysteamine treatments to determine whether alterations of hepatic NPSH status could contribute to their observed protective actions. D(+)-Galactosamine HC1 (400 mg/kg, ip) was administered to male Sprague-Dawley rats at 8 pm. Cystamine diHC1 (300 mg/kg, po) or cysteamine HC1 (170 mg/kg, ip) were administered 12 hr after GAL. Hepatic NPSH levels were determined using Ellman's reagent. Hepatic cysteamine levels were determined by separating NPSH Ellman's derivatives by reversed phase HPLC. Cystamine and cysteamine caused transient elevation of NPSH levels of 1-2 nanomoles/mg liver which correlated with the presence of 1-2 nanomoles of cysteamine/mg liver. However, neither cystamine nor cysteamine prevented NPSH levels from falling to 3 nanomoles/mg tissue 24 hr after GAL. Hepatoprotective treatments did not affect long term NPSH status in GAL-poisoned rats. However, transient NPSH increases, due to the intrahepatic presence of cysteamine, may contribute to the therapeutic effects of these hepatoprotective agents.

Factors effective in reducing rat mortality due to acute liver failure as induced by D-galactosamine poisoning

Mortality from D-galactosamine hydrochloride (D-GalN)-induced acute liver failure (ALF) in rats can be reduced by (1) transplanting intact hepatocytes; (2) injecting cytosol from fractionated hepatocytes dispersed from a liver subjected to 70% hepatectomy 24 hr earlier (CYT-H); (3) injecting a cell-free supernate derived from cultured hepatocytes (SUP); or (4) injecting neuraminidase-treated plasma where the plasma is drawn 24 hr after donor rats are subjected to 70% hepatectomy (PHP-neu). These treatments are effective when administered 20-24 hr after D-GalN poisoning, but experiments to determine the alterations in mortality rates as a function of time of treatment in relation to poisoning have not been performed. Two experiments are reported here. In the first the survival of lethally poisoned rats was compared after intravenously injecting either SUP prepared from cultured hepatocytes of syngeneic adult or fetal rat sources, or CYT-H from syngeneic adult rats 20 hr after poisoning. Untreated rats, rats treated with culture media alone, or rats treated with CYT from a nonregenerating source had an 88-100% mortality, with all deaths occurring within 72 hr following poisoning. Improved survival followed all other treatments: 55% of the rats receiving adult SUP, 70% of the rats receiving fetal SUP, and 80% of the rats receiving CYT-H survived. In the second experiment the survival of poisoned rats was compared after injecting them with PHP-neu, PHP not treated with neuraminidase (PHP without neu), and neuraminidase-treated plasma from sham-operated rats (SP-neu) or normal, nonoperated rats (NP-neu) 20 hr after poisoning.(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical markers in carbon-tetrachloride-and galactosamine-induced acute liver injuries: the effects of dihydroquinoline-type antioxidants

The pharmacological action and possible therapeutic uses of some recently developed synthetic, non-toxic dihydroquinoline-type antioxidants were studied. The effect of the lipid-soluble 6,6-methylene-bis (2,2,4-trimethyl-1,2-dihydroquinoline) (n = 1, 2 or 3) (MTDQ) on carbon-tetrachloride-induced acute liver injuries was investigated, and that of the water-soluble 6,6-methylene-bis (2,2-dimethyl-4-methansulphonic acid sodium-1,2-dihydroquinoline) (MDS) on galactosamine-induced acute liver injuries in CFLP mice (Lati, Hungary). MTDQ was found suitable for the prevention of acute CCl4-induced liver injuries and MDS for that of acute galactosamine-induced liver injuries. Disappearance or significant diminution of the morphological signs and lesions of lipid degeneration and centro-lobular liver necrosis, decrease of serum GOT activities, and also inflammatory changes induced by galactosamine were observed.

Protective effect of (+)cyanidanol-3 in acute liver injury induced by galactosamine or carbon tetrachloride in the rat

Pretreatment of rats with (+)cyanidanol--3 decreases the alterations in liver function tests (transaminase and bilirubin) as well as the accumulation of hepatic triglycerides induced by acute doses of galactosamine or carbon tetrachloride. This action was related to the dose of (+)cyanidanol-3 administered. The lowest effective doses were 3 intraperitoneal injections of 125 mg/kg administered before galactosamine or carbon tetrachloride. In the case of carbon tetrachloride intoxication, in vivo administration of (+)cyanidanol-3 reduced to a slight extent the absorption of conjugated dienes produced in liver microsomal lipid. This observation confirms that (+)cyanidanol-3 is able to prevent lipid peroxidation in vivo. As the protective effect of (+)cyanidanol-3 becomes apparent in two types of intoxication which are very different in their primary mechanisms of action, it is suggested that, the flavonoid also acts on a later stage of the process leading to necrosis and steatosis of the liver.

The influence of ethanol pretreatment on the effects of nine hepatotoxic agents

The hepatotoxic effects of carbon tetrachloride (0.01 ml/kg i.p.), thioacetamide (50 mg/kg intraperitoneally), paracetamol (0.5 g/kg intraperitoneally), and allyl alcohol (0.05 ml/kg intraperitoneally) as estimated by determination of serum enzyme activities (GOT, GPT, SDH) were enhanced in mice treated with one oral dose of 4.8 g/kg ethanol 16 hrs. previously. Pretreatment of mice with ethanol did not increase the hepatotoxic actions of bromobenzene (0.25 ml/kg intraperitoneally), phalloidin (1.5 mg/kg intraperitoneally), alpha-amanitin (0.75 mg/kg intraperitoneally), and praseodymium (12 mg/kg intravenously) though there was a trend to higher enzyme activities in the case of bromobenzene. In guinea-pigs ethanol also aggravated CCl4-induced liver damage, but only strengthened the hepatotoxic activity of D-galactosamine (150 mg/kg intraperitoneally). Treatment with 4.8 g/kg ethanol did not influence liver glutathione levels in mice but increased aniline hydroxylation in the 9000 x g liver homogenate supernatant of mice and guinea-pigs. A dose of 2.4 g/kg ethanol, on the other hand, neither increased aniline hydroxylase activity nor enhanced carbon tetrachloride-induced hepatotoxicity in mice. It is assumed that the enhanced sensitivity to hepatotoxic agents after treatment with ethanol may be due to an enhanced microsomal activation of these substances.

Studies of liver phosphorylase in hepatic injuries. I. Alteration in enzyme activity

Phosphorylase activities (total and a form) were determined in the livers of experimental hepatic injuries with carbon tetrachloride or galactosamine and the livers of patients with liver diseases. Experimental liver injuries caused a slight decrease in total activity in later stages and a marked increase in a form activity in earlier stages. In human livers, low values of total activity were found in acute hepatitis and cirrhosis of the liver with no consistent alteration in a activity. Phosphorylase activities in hepatocellular carcinomas were also low. The importance of the altered phosphorylase activities in hepatic injuries is discussed in relation to the disorder in glycogen metabolism in the injured liver.

Investigations on d-galactosamine hepatitis after pretreatment with alpha-hexachlorocyclohexane

D-Galactosamine hepatitis cannot be induced in rapidly replicating liver tissue at various times after induction of proliferation. Proliferation was induced by administration of alpha-hexachlorocyclohexane. The morphological features of galactosamine hepatitis do not appear or are very mild. The onset of DNA synthesis is delayed to about 12 hrs as also shown in partially hepatectomized rats.

[The effect of silybin-dihemisuccinate on regulation disorders in phospholipid metabolism in acute galactosamine intoxication in the rat]

1. 24 h after application of 900 mg D-galactosamine/kg body weight, an increase of total lipids, triglycerides, phosphatidyl-choline and phosphatidic acid concentrations, and also a decrease of total phospholipids and phosphatidylethanolamine can be determined in the whole rat liver. After administration of [1-14C]-palmitate, specific radioactivity of phosphatidyl-choline is diminished without alteration of specific radioactivity of other lipid fractions. Prophylactic application of silybin-dihemisuccinate abolished completely decrease of phosphatidyl-ethanolamine and diminished increase of total lipids and triglyceride concentrations. 2. Specific radioactivity of total lipids in serum of galactosamine-intoxicated rats is enhanced, specific radioactivity of triglycerides and phospholipids is diminished, simultaneously, total lipids concentration is reduced. 3. In the microsomal fraction of galactosamine-injured livers, a decrease of specific radioactivity of total phospholipids and phosphatidyl-choline can be observed. Prophylactic administration of silybin abolishes diminution of specific radioactivity of phosphatidyl-choline partially. 4. Diminution of specific radioactivity of total lipids, total phospholipids and phosphatidyl-ethanolamine, induced by galactosamine intoxication in the mitochondrial fraction, is normalized by application of silybin. 5. Diminished triglyceride infiltration in siybin-treated rats may be based onnormalization of inhibited phosphatidyl-choline turnover.