In vitro induction of nitric oxide by fructose-1,6-diphosphate in the cardiovascular system of rats

Nitric oxide (NO) functions as a cellular messenger in a number of organs and cell systems in the cardiovascular system (CVS); it is a significant determinant of basal vascular tone and regulates myocardial contractility and platelet aggregation. The present study focused upon understanding the in vitro effects of fructose-1,6-diphosphate (FDP) on the rat cellular NO pathway. The iNOS activity was measured by monitoring the formation of (³H)-citrulline in 50,000 g soluble fractions of crude homogenates of endothelial (ET) and smooth muscle cells (SMC) from the arteries of rats, and macrophages (MAC) and lymphocytes (LYM) from rat blood. FDP in concentrations of 10-1000 M stimulated rat cellular iNOS activity in a concentration-dependent manner. FDP-stimulated rat cellular iNOS was found to be completely reversed by 5 M concentration of NG-monomethyl-L-arginine (L- NMMA), the potent mammalian NOS inhibitor. These studies demonstrated that FDP may induce the formation of NO by stimulating rat cardiovascular iNOS activity.     

Physical conditioning modulates rat cardiac vascular endothelial growth factor gene expression in nitric oxide-deficient hypertension

Many individuals with cardiac diseases undergo periodic physical conditioning with or without medication to improve cardiovascular health. Therefore, this study investigated the interaction of physical training and chronic nitric oxide synthase (NOS) inhibitor (nitro-L-arginine methyl ester, L-NAME) treatment on blood pressure (BP), cardiac vascular endothelial factor (VEGF) gene expression, and nitric oxide (NO) systems in rats. Fisher 344 rats were divided into four groups and treated as follows: (1) sedentary control, (2) exercise training (ET) for 8 weeks, (3) L-NAME (10mg/kg, s.c. for 8 weeks), and (4) ET+L-NAME. BP was monitored with tail-cuff method. The animals were sacrificed 24h after last treatments and hearts were isolated and analyzed. Physical conditioning significantly increased respiratory exchange ratio, cardiac NO levels, NOS activity, endothelial eNOS, and inducible iNOS protein expression as well as VEGF gene expression. Training also caused depletion of cardiac malondialdehyde (MDA) levels indicating the beneficial effects of the training. Chronic L-NAME administration resulted in a depletion of cardiac NO level, NOS activity, and eNOS, nNOS, and iNOS protein expressions, as well as VEGF gene expression (2-fold increase in VEGF mRNA). Chronic L-NAME administration also enhanced cardiac MDA levels indicating cardiac oxidative injury. These biochemical changes were accompanied by increases in BP after L-NAME administration. Interaction of training and NOS inhibitor treatment resulted in normalization of BP and up-regulation of cardiac VEGF gene expression. The data suggest that physical conditioning attenuated the oxidative injury caused by chronic NOS inhibition by up-regulating the cardiac VEGF and NO levels and lowering the BP in rats.     

Hepatic polyamines and related enzymes following chlordecone-potentiated carbon tetrachloride toxicity in rats

Chlordecone potentiation of the hepatotoxic and lethal effects of CCL4 has been well established. Recent studies have shown that the suppression of hepatocellular regeneration results in an accelerated progression of liver injury leading to complete hepatic failure. Since polyamines are involved in cell division, these studies were designed to investigate the polyamine levels and associated enzymes in the livers of rats treated with a low-dose combination of CD and CCl4. For comparison, a large toxic dose of CCl4 was also employed. The extent of liver toxicity in rats fed 10 parts per million chlordecone (CD) for 15 days and subsequently injected with a single dose of CCl4 (100 microL/kg body weight) or a high dose of CCL4 alone (2.5 mL/kg body weight) was similar 6 and 24 hr later as assessed by plasma transaminase levels. There was significant elevation in liver ornithine decarboxylase, S-adenosylmethionine decarboxylase, and putrescine at 24 hr and spermidine N1-acetyltransferase, N1-acetylputrescine, putreanine, putrescine, and N1-acetylspermidine at 6 hr in rats treated with the high dose of CCl4 alone compared to the combination treatment. Spermidine levels decreased up to 6 hr and then increased up to 24 hr for both treatments. Spermine continuously decreased up to 24 hr for the CD and CCl4 low-dose combination treatment compared to rats treated with a high dose of CCl4 alone. Spermidine levels were lower than in controls and rose towards control value between 6 and 24 hr after the combination treatment and the high dose of CCl4. Results indicate that the CD and CCl4 low-dose combination treatment increased liver toxicity, resulting in compromised polyamine metabolism that is coincidental with suppressed hepatocellular regeneration, which leads to an accelerated progressive phase of liver injury and culminates in complete hepatic failure.     

L-tryptophan administration promotes the reversion of pre-established chronic liver injury in rats treated with carbon tetrachloride

We examined the effect of L-tryptophan (Trp) administration on the reversion of CCl(4)-induced chronic liver injury after hepatotoxicant withdrawal in rats. When rats treated with CCl(4) twice a week for 6 weeks were released from CCl(4) treatment for 2 weeks, there was an incomplete reversion of liver injury. The reversion was enhanced by 2 weeks of daily intraperitoneal administration of Trp (50 mg/kg body weight), starting just after CCl(4) withdrawal. There were increases in the levels of thiobarbituric acid reactive substances, an index of lipid peroxidation, Ca(2+), triglycerides, and Trp, and decreases in tryptophan 2,3-dioxygenase activity and serum triglyceride concentrations in the liver of rats treated with CCl(4) for 6 weeks. Serum albumin concentrations and in vitro hepatic protein synthesis activity did not change in the CCl(4)-treated rats. The changes in the CCl(4)-treated rats were partially attenuated 2 weeks after CCl(4) withdrawal. The attenuation was enhanced by 2 weeks of daily Trp administration. The increases in hepatic thiobarbituric acid reactive substances and triglycerides and the decreases in hepatic tryptophan 2,3-dioxygenase activity and serum triglyceride concentrations observed 2 weeks after CCl(4) withdrawal were almost completely attenuated by Trp administration. In vitro hepatic protein synthesis in CCl(4)-treated and untreated rats was increased by 2 weeks of daily Trp administration. These results indicate that Trp administration promotes the reversion of pre-established chronic liver injury in rats treated with CCl(4,) and suggest that Trp exerts this effect by enhancing the improvement of several parameters of liver dysfunction associated with chronic liver injury and by stimulating hepatic protein synthesis.     

大鼠实验性乙醇胃粘膜损伤中一氧化氮合成酶和内皮素合量的变化及意义

目的 :探讨一氧化氮和内皮素在急性乙醇胃粘膜损伤中的作用及其相互关系。方法 :采用大鼠乙醇胃粘膜损伤模型 ,测定其胃粘膜内一氧化氮合成酶 (NOS)和内皮素 (ET)含量并观察其胃粘膜病理变化。结果 :随着乙醇作用时间延长和胃粘膜损伤的加重 ,胃粘膜内ET含量显著上升 (P <0 .0 5 ) ,而NOS的含量显著下降 (P <0 .0 5 ) ,两者呈负相关。结论 :胃粘膜内ET释放增加和NOS活性下降参与了急性乙醇胃粘膜损伤的病理生理过程。     

Studies on cytochrome oxidase in carbon tetrachloride treated rats

Cytochrome c oxidase was purified from control and CCl4 treated rats and its kinetic properties were studied. The activity of the enzyme was inhibited by 51% in CCl4 (4 g per kg body weight for 24 hr) treated rats. Studies on the kinetic properties showed that the K(m) of the enzyme increased by 60% while Vmax decreased by 44% in CCl4 treated rats compared to controls. The content of cytochrome aa3 was decreased by 34% while cytochrome b and c were not affected by CCl4 treatment. Phosphatidylcholine, phosphatidylethanolamine and cardiolipin were decreased significantly by 40%, 49% and 60% respectively in CCl4 treated rats. A decrease in the cytochrome aa3 content and a change in the lipid environment of the membrane are probably responsible for a decreased rate of electron transfer from cytochrome c to oxygen.     

Oxidative injury due to chronic nitric oxide synthase inhibition in rat: effect of regular exercise on the heart

Many individuals with cardiac diseases undergo periodic physical conditioning with or without medication. Therefore, this study investigated the interaction of physical training and chronic nitric oxide synthase (NOS) inhibitor (nitro-L-arginine methyl ester, L-NAME) treatment on blood pressure (BP), heart rate (HR) and cardiac oxidant/antioxidant systems in rats. Fisher 344 rats were divided into four groups and treated as follows: (1) sedentary control (SC), (2) exercise training (ET) for 8 weeks, (3) L-NAME (10 mg/kg, s.c. for 8 weeks) and (4) ET+L-NAME. BP and HR were monitored with tail-cuff method. The animals were sacrificed 24 h after last treatments and hearts were isolated and analyzed. Physical conditioning significantly increased respiratory exchange ratio (RER), cardiac nitric oxide (NO) levels, NOS activity and endothelial (eNOS) and inducible (iNOS) protein expression. Training significantly enhanced cardiac glutathione (GSH) levels, GSH/GSSG ratio and up-regulation of cardiac copper/zinc-superoxide dismutase (CuZn-SOD), manganese (Mn)-SOD, catalase (CAT), glutathione peroxidase (GSH-Px) activity and protein expression. Training also caused depletion of cardiac malondialdehyde (MDA) and protein carbonyls. Chronic L-NAME administration resulted in depletion of cardiac NO level, NOS activity, eNOS, nNOS and iNOS protein expression, GSH/GSSG ratio and down-regulation of cardiac CuZn-SOD, Mn-SOD, CAT, GSH-PX, glutathione-S-transferase (GST) activity and protein expression. Chronic L-NAME administration enhanced cardiac xanthine oxidase (XO) activity, MDA levels and protein carbonyls. These biochemical changes were accompanied by increases in BP and HR after L-NAME administration. Interaction of training and NOS inhibitor treatment resulted in normalization of BP, HR and up-regulation of cardiac antioxidant defense system. The data suggest that physical conditioning attenuated the oxidative injury caused by chronic NOS inhibition by up-regulating the cardiac antioxidant defense system and lowering the BP and HR in rats.     

Kinetic alterations of cytochrome c oxidase in carbon tetrachloride induced cirrhotic rat liver

In a study of the chronic effects of CCl4 on the respiratory activities of rat liver mitochondria, the content of cytochrome c oxidase increased from 0.077 +/- 0.010 (nmol/mg protein) for normal rats to 0.101 +/- 0.009, and its specific activity increased from Vmax = 345 +/- 24 (e-/s/cytochrome aa3) to 431 +/- 19 in mitochondria of CCl4 treated rats. There was a slight increase in Km for cytochrome c from 5.63 +/- 0.08 microM to 7.79 +/- 0.80. These results would strongly suggest that an appreciable decrease in the steady state concentration of ATP in hepatic cells of CCl4 treated rats brought about a compensatory increase in the overall activity of cytochrome c oxidase. However, when the rate of oxygen uptake by mitochondria was measured in the presence of rotenone and tetramethyl-p-phenylene-diamine with NADH as substrate, the specific activity in CCl4 treated rats was lower than that of normal rats (Vmax = 345 +/- 31 (e-/s/cytochrome aa3), as compared to Vmax = 408 +/- 21) in spite of the increased activity of cytochrome c oxidase. This phenomenon was ascribed to a decrease in the activity of NADH cytochrome b5 reductase in the mitochondrial outer membrane due to CCl4 treatment.     

Protective effects of vitamin E on carbon tetrachloride-induced liver damage in rats

In this study we investigated whether the increase of hepatic vitamin E content by intraperitoneal administration, influences chronic liver damage induced by carbon tetrachloride (CCl(4)) in rats. Thirty adult male Wistar rats were divided into three groups. The first group was used as a control and the rats in the second group were administered CCl(4) in olive oil subcutaneously. Rats in the third group were administered intraperitoneally vitamin E (dl-alpha-tocopherol acetate, 100 mg kg(-1)). This administration was performed three times per week for five weeks. Liver samples were used for the determination of vitamin E levels, glutathione peroxidase (GSHPx) activities and histological examination. Serum levels of alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase, aspartate aminotransferase, gamma-glutamyltranspeptidase, total and conjugated bilirubin were significantly (p<0.05, p<0.01, p<0.001) higher in animals treated with CCl(4) than in the controls and had returned to normal values by the administration of vitamin E + CCl(4 ). Liver vitamin E levels were significantly (p<0.05) lower in the CCl(4) group than in the control group. However, the liver vitamin E content was significantly (p<0.01, p<0.001) increased in the vitamin E + CCl(4) injected group. On the other hand, liver GSHPx activity was not statistically different among the groups. On histological examination, vitamin E administered animals showed incomplete, but significant, prevention of liver necrosis and cirrhosis induced by CCl(4 ). these data indicate that intraperitoneally administered vitamin E has protective effects against CCl(4)-induced chronic liver damage and cirrhosis as evidenced by biochemical data and conventional histological examination.     

Possible role of platelet activating factor (PAF) in disseminated intravascular coagulation (DIC), evidenced by use of a PAF antagonist, CV-3988

The i.v. infusion of endotoxin (ET) (0.25 mg/kg/hr for 4 hr) induced disseminated intravascular coagulation (DIC) in rats; thrombocytopenia, prolongation of prothrombin time (PT) and partial thromboplastin time (PTT), hypofibrinogenemia and elevated levels of fibrinogen/fibrin degradation products (FDP) were observed. Platelet activating factor (PAF) (8 micrograms/kg/hr for 4 hr) also induced DIC-like changes, except in platelets. A specific PAF antagonist, CV-3988 (2 mg/kg bolus 5 min before ET + 1 or 2 mg/kg/hr for 4 hr of ET infusion) improved all the parameters that had been altered by both ET and PAF. CV-3988 (2 mg/kg bolus 2 hr after ET + 2 mg/kg/hr for 2 hr of ET infusion) also had beneficial effects on DIC. CV-3988 itself had no effects on the parameters of DIC. These results strongly suggest that PAF may play a role in the pathogenesis of DIC and CV-3988 may prove to be useful for the treatment of DIC.     

Effects of melatonin on carbon tetrachloride-induced changes in rat serum

Carbon tetrachloride (CCl4) is a volatile organic chemical, which causes tissue damage, especially to the liver and kidney. In experimental animals it has been shown to be carcinogenic. This study was designed to evaluate the effects of exogenous melatonin administration on the CCl4-induced changes of some biochemical parameters in rat blood. Twenty-four male Wistar rats were randomly divided into three equal groups: Control, CCl4 and CCl4 plus melatonin (CCl4+MEL). Rats in CCl4 group were injected subcutaneously with CCl4 0.5 ml/kg in olive oil while rats in CCl4+MEL group were injected with CCl4 (0.5 ml/kg) plus melatonin (25 mg/kg in 10% ethanol) every other day for one month. Control rats were treated with olive oil. Serum urea, creatinine, total protein, albumin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), total and conjugated bilirubin, alkaline phosphatase (ALP), gamma-glutamyl transferase (gamma-GT), total iron, and magnesium levels were determined. Serum AST, ALT, total and conjugated bilirubin, ALP, gamma-GT, and total iron levels were significantly higher in CCl4-treated rats than in the controls, while urea, total protein, and albumin levels were significantly lower. Melatonin treatment did not cause a significantly change in serum urea, total protein, and albumin levels. However, the elevations in AST, ALT, total and conjugated bilirubin, ALP, gamma-GT, and total iron levels induced by CCl4 injections were significantly reduced by melatonin. On the other hand, melatonin administration significantly decreased serum magnesium levels. These results indicate that melatonin could be a protective agent against the CCl4 toxicity in rats, most likely through its antioxidant and free radical scavenger effects.     

Inhibitors of inducible nitric oxide (NO) synthase are more effective than an NO donor in reducing carbon-tetrachloride induced acute liver injury

The exact functional role of nitric oxide (NO) in liver injury is currently a source of controversy. NO is enzymatically synthesized by nitric oxide synthase (NOS). In this study, we assessed the role of inducible NOS (iNOS) in carbon tetrachloride (CCl4)-induced acute liver injury using inhibitors of iNOS, and an NO donor. Adult ICR mice were injected with CCl4 with or without the iNOS inhibitors (5-methylisothiourea hemisulfate [SMT] and l-N6-(1-iminoethyl)-lysine [L-NIL]) and an NO donor (Sodium Nitroprusside [SNP]). Blood and liver tissues were collected for analysis. Immunohistochemistry (IHC), serum alanine aminotransferase (ALT), serum total 8-isoprostane analysis, RT-PCR, Western Blotting (WB) and EMSA were done. Our results showed increased levels of ALT, necrosis, total 8-isoprostane and nitrotyrosine after CCl4 administration. iNOS inhibitors and SNP abrogated these effects but the effect was more pronounced with SMT and L-NIL. RT-PCR, WB and IHC in CCl4-treated mice demonstrated upregulation of TNF-alpha, iNOS, and COX-2. The administration of iNOS inhibitors with CCl4 diminished the expression of these proinflammatory mediators. NF-kappaB was also upregulated in CCl4-treated mice and was reversed in mice pretreated with iNOS inhibitors. SNP pretreated mice also showed a lower expression of COX-2 when compared with CCl4 treated mice but TNF-alpha, iNOS and NF-kappaB activity were unaffected. We propose that a high level of nitric oxide is associated with CCl4-induced acute liver injury and the liver injury can be ameliorated by decreasing the NO level with iNOS inhibitors and an NO donor with the former more effective in reducing CCl4-induced liver injury.     

Hepatoprotective action of ethanolic extracts of Melia azedarach Linn. and Piper longum Linn and their combination on CCl4 induced hepatotoxicity in rats

A comparison of analysis in evaluating the hepatoprotective action of ethanolic extract of M. azedarach (MAE) and P. longum (PLE) with their combination biherbal extract (BHE) against carbon tetrachloride (CCl4) induced hepatic damage is reported in albino rats. There was a marked elevation of serum marker enzyme levels in CCl4 treated rats, which were restored towards normalization in the drug (MAE and/or PLE:50 mg/kg body weight po, once daily for 14 days) treated animals. The biochemical parameters like total protein, total bilirubin, total cholesterol, triglycerides, and urea were also restored towards normal levels. The combined BHE showed more significant reduction of the enzymes than MAE or PLE against CCl4 induced hepatotoxicity. The results strongly indicate that BHE has more potent hepatoprotective action than MAE or PLE individually against CCl4 induced hepatic damage in rats. Among these extracts, BHE showed similar hepatoprotective action to silymarin, which was the positive control in this study.     

Exercise conditioning attenuates the hypertensive effects of nitric oxide synthase inhibitor in rat

Many individuals with cardiovascular diseases undergo periodic exercise conditioning with or with out medication. Therefore, this study investigated the interaction of exercise training and chronic nitric oxide synthase (NOS) inhibitor (Nitro-L-Arginine Methyl Ester, L-NAME) treatment on blood pressure and its correlation with aortic nitric oxide (NO), antioxidant defense system and oxidative stress parameters in rats. Fisher 344 rats were divided into four groups: (1) sedentary control, (2) exercise training (ET) for 8 weeks, (3) L-NAME (10 mg/kg, subcutaneous for 8 weeks) and (4) ET + L-NAME. Blood pressure (BP) was monitored weekly for 8 weeks with tail-cuff method. The animals were sacrificed 24 h after last treatments and thoracic aortic rings were isolated and analyzed. Exercise conditioning resulted in a significant increase in respiratory exchange ratio (RER), aortic NO production, NO synthase activity and inducible iNOS protein expression. Training significantly enhanced aortic GSH levels, GSH/GSSG ratio and up-regulation of aortic CuZn-SOD, Mn-SOD, catalase (CAT) glutathione peroxidase (GSH-Px) activity and protein expression and significantly decreased aortic lipid peroxidation. Chronic L-NAME administration resulted in a significant depletion of aortic NO, NOS activity, endothelial (eNOS) and iNOS protein expression, GSH level, GSH/GSSG ratio, down-regulation of aortic antioxidant enzyme activities and protein expressions. Aortic xanthine oxidase (XO) activity significantly increased with increased lipid peroxidation and protein oxidation after L-NAME administration. The biochemical changes were accompanied by increased in BP. Interaction of training and chronic NOS inhibitor treatment resulted in normalization of BP and aortic antioxidant enzyme activity and protein expression, up-regulation of aortic GSH/GSSG ratio, NO levels, Mn-SOD protein expression, depletion of GSSG, protein oxidation and lipid peroxidation. The data suggest that training attenuated the oxidative injury caused by chronic NOS inhibitor treatment by up-regulating the NO and antioxidant systems and lowering the BP in rats.     

Enhanced hepatotoxicity and inhibition of liver endoplasmic reticulum calcium pump by CCl4 in rats fed a thiamine deficient diet

Male Sprague-Dawley rats were fed a thiamine deficient diet for three weeks, then treated with a range of CCl4 doses (0.01-1-ml/kg). Rats fed the deficient diet grew more slowly (body weight 65 percent of control) and had elevated liver glutathione (GSH) (220 percent of control). CCl4 hepatotoxicity, assessed by serum glutamicpyruvic transaminase (SGPT) activity and histological examination 24 hours after the hepatotoxin, was augmented in the group fed the thiamine deficient diet. Likewise, CCl4 inhibition of liver endoplasmic reticulum (ER) function (glucose-6-phosphatase (G6Pase) and calcium pump activities one hour after CCl4) was enhanced in rats fed the deficient diet. These results suggest that thiamine deficiency enhances CCl4 damage to membranes of the ER and enhances CCl4 hepatotoxicity.     

Effect of ovarian steroids on nitric oxide synthase in the rat uterus, cervix and vagina

The effects of estrogen (E2), progesterone (P) and E2 and P (E2 + P) were examined on nitric oxide synthase (NOS) activity in both cytosolic and particulate fractions isolated from the rat uterus, vagina, cervix and cerebral cortex. Additionally plasma nitrate + nitrite (NO3 + NO2) levels were measured in control and hormone treated rats. Cytosolic NOS was the predominant form being approximately 80% of the total in all four tissues. NOS activity in both fractions from all tissues was highly Ca-dependent (> 90%). Among the reproductive tract tissues, the highest activity was found in the cervix, which was nearly 5- and 2-fold higher than the uterus and vagina, respectively. NOS activity in the cerebral cortex was by far the highest being 5-fold higher than in the cervix. In contrast to the cortex, E2 treatment downregulated cytosolic NOS in all reproductive tract tissue, but this was statistically significant in only uterus. When compared with E2 treated rats, P increased cytosolic NOS in uterus, vagina, and particulate NOS in the cervix. The data do not give any indication whatsoever of differential effects of P in the uterus and cervix.     

Antifibrogenic effect in vivo of low doses of insulin-like growth factor-I in cirrhotic rats.

Insulin-like growth factor-I (IGF-I) is produced mainly in the liver and it induces beneficial effects on the nutritional status, the liver function and oxidative hepatic damage in cirrhotic rats. The aim of this work was to analyze the effect of IGF-I on mechanisms of fibrogenesis in cirrhotic rats. Liver cirrhosis was induced by CCl(4) inhalation and phenobarbital in Wistar rats. Ten days after stopping CCl(4) administration (day 0), rats received either IGF-I (2 microg/100 g bw/day) (CI+IGF) or saline (CI) subcutaneously during 14 days. Animals were sacrificed on day 15. As control groups were used: healthy rats (CO) and healthy rats treated with IGF-I (CO+IGF). Liver histopathology, hydroxyproline content, prolyl hydroxylase activity, collagen I and III mRNA expression and the evolution of transformed Ito cells into myofibroblasts were assessed. Among the two control groups (CO+IGF), no differences were found in hydroxyproline content and these levels were lower than those found in the two cirrhotic groups. Compared with untreated cirrhotic rats, the CI+IGF-I animals showed a significant reduction in hydroxyproline content, prolyl hydroxylase activity and collagen alpha 1(I) and alpha1(III) mRNA expression. A higher number of transformed Ito cells (alpha-actin +) was observed in untreated cirrhotic animals as compared to CO and CI+IGF groups. In summary, treatment with IGF-I reduced all of the studied parameters of fibrogenesis. In conclusion, low doses of IGF-I induce in vivo an antifibrogenic effect in cirrhotic rats.     

The effects of dietary flaxseed on the Fischer 344 rat. III. Protection against CCl(4)-induced liver injury

The hepatotoxic effect of carbon tetrachloride (CCl(4)) administered by gavage at 0.25 ml CCl(4) (1:1 in olive oil) per 100 g body weight was examined 24 h later in regular chow fed (RC) and 10% flax chow fed (FC) male and female Fischer 344 rats. CCl(4)-treated RC rats were subdued, lethargic and unkempt. CCl(4)-treated FC rats were much less affected. CCl(4) treatment resulted in loss of weight in RC and FC rats. In males, the weight loss was 6.7% body mass in RC rats compared to 5.6% body mass in FC rats. In females, the weight loss was 7.5% body mass in both RC and FC rats. While CCl(4) treatment increased the level of the liver injury marker plasma alanine aminotransferase (ALT) in RC rats, this CCl(4) effect was significantly attenuated in FC rats. In male rats, the ALT increase was 435-fold in RC rats and 119-fold in FC rats, over that of their respective controls. In female rats, the ALT increase was 454-fold in RC rats and 381-fold in FC rats, over that of their respective controls. These results provide evidence that flax consumption protects the liver against injury and that the extent of the protection is sex dependent. CCl(4) had no effect on the plasma level of gamma-glutamyltranspeptidase (gammaGT) in RC and FC rats supporting the contention that plasma gammaGT is not a useful marker for acute liver injury which is seen in this model. The activity of gammaGT was increased in the livers of FC rats compared to RC rats: 2.7-fold in males and 1.5-fold in females. In RC rats, the activity of liver gammaGT was decreased by CCl(4) treatment: 70% in the male and 25% in the female. However, this CCl(4) effect was reversed or abolished by flax consumption. Compared to RC rats: in male FC rats, CCl(4) actually increased the activity of liver gammaGT 1.28-fold; while in female FC rats, the depressing effect of CCl(4) treatment was abolished. The flax-induced preservation of gammaGT in the liver in response to injury may be involved in the observed hepatoprotection through generation of GSH. In RC male rats, CCl(4) treatment effected a 25% reduction in plasma glucose levels. There was no decrease in CCl(4)-treated FC male rats. In female rats, CCl(4) treatment effected a 21% decrease in plasma glucose levels in both RC and FC rats. In conclusion, multiple parameters for acute CCl(4)-induced injury were attenuated in the FC compared to the RC rat. That flaxseed consumption conferred greater protection against liver injury in the male than in the female suggests an involvement of the estrogenic lignan component of flaxseed. We discuss the possibility that this hepatoprotection is through a flax lignan-induced increase in reduced glutathione related to a flax effect on the activity of liver gammaGT in the resting state and the maintenance of its activity in response to injury.     

Effects of ventromedial and lateral hypothalamic stimulation on chemically-induced liver injury in rats

The effects of hypothalamic stimulation on experimental liver injury induced by carbon tetrachloride (CCl4) or dimethylnitrosamine (DMN) were studied in rats, by measuring plasma alanine aminotransferase (ALT) activity as an index of acute liver injury. Electrical stimulation of the ventromedial hypothalamus (VMH) in CCl4-treated rats caused a marked increase in plasma ALT activity, accompanied by a significant decrease in ALT activity in the liver, although CCl4 treatment alone had no significant effect on plasma ALT activity. A similar effect of VMH stimulation on plasma ALT activity was observed in rats treated with DMN, another hepatotoxic chemical. No such exaggerated effect of VMH stimulation on plasma ALT activity was observed after stimulation of the lateral hypothalamic area (LH). Surgical sympathetic denervation of the liver greatly suppressed the increase in plasma ALT activity after CCl4 injection and VMH stimulation. Measurement of regional blood flow indicated that VMH stimulation did not produce a significant change in blood flow to the liver. These results suggest that the VMH is involved in the progress of chemically-induced liver injury through activation of the sympathetic nerve (hepatic nerves), possibly by affecting liver metabolism more than the blood flow change to the liver.