Intraperitoneal Injection Of Thioacetamide Research Articles

The effects of early and late administration of inhibitors of inducible nitric oxide synthase in a thioacetamide-induced model of acute hepatic failure in the rat

Background/Aims: Nitric oxide (NO) is a pivotal mediator of inflammation. Its role in acute hepatic failure (AHF) is controversial. We investigated the role of NO, and the hypothesis that inhibition of inducible NO synthase (iNOS) activity would improve outcome in liver failure in rats, using the iNOS inhibitors l-NAME and aminoguanidine (AMG). Methods: AHF was induced by two intraperitoneal injections of thioacetamide (TAA). Seven groups ( n=10) were studied. Group I: TAA alone. Groups II, III and IV were additionally pre-treated with the NO precursor l-arginine (300 mg/kg i.p.), or iNOS inhibitors AMG (100 mg/kg s.c.), or N G-nitro- l-arginine methyl ester ( l-NAME) (100 mg/kg s.c.) for 5 days, respectively. Groups V, VI and VII received l-arginine, AMG or l-NAME commencing immediately after TAA administration. Clinical and biochemical parameters were assessed serially, and mortality investigated in further similar cohorts for each regime. Results: AMG, pre-treatment but not post-treatment, significantly improved outcome including mortality (10 vs. 70%, P<0.005). The less selective iNOS inhibitor l-NAME was not beneficial. Arginine pre-and post-treatment, and iNOS inhibition post-treatment, worsened clinical parameters of TAA-induced liver failure. Conclusions: Administration of the iNOS inhibitor AMG prior to insult reduces the severity of damage and improves mortality.

Leptin receptor-mediated signaling regulates hepatic fibrogenesis and remodeling of extracellular matrix in the rat

In this study, we investigated the role of leptin and its receptors (Ob-R) in profibrogenic responses in the liver using Zucker (fa/fa) rats, a natural occurring Ob-R-deficient animal. Male Zucker (fa/fa) rats and their lean (+/?) littermates were given intraperitoneal injections of thioacetamide (TAA) (200 mg/kg body wt, 3 times/wk) for 4-8 weeks, and progression of hepatic fibrosis was evaluated. In vitro transactivation of hepatic stellate cells (HSCs) isolated from Zucker rats was evaluated by Western blotting and immunocytochemistry for alpha-smooth muscle actin and type I collagen. Further, a long-form Ob-R (Ob-Rb) in sinusoidal endothelial cells (SECs) and Kupffer cells was identified by reverse-transcription polymerase chain reaction. Moreover, transforming growth factor (TGF)-beta1 messenger RNA in LSE cells, a human SEC-derived cell line, was measured by Northern blotting. Although the normal liver does not produce leptin, activated HSCs produced leptin in vivo during fibrogenesis caused by TAA. In Zucker rats, TAA-induced hepatic fibrosis was prevented almost completely, whereas induction of TGF-beta1 and activation of HSCs were abolished. It is less likely, however, that leptin plays an essential role in the activation of HSCs as a strong autocrine regulator, because HSCs isolated from Zucker rats undergo normal transactivation process in vitro. In contrast, SECs and Kupffer cells contain Ob-Rb, through which leptin up-regulates the expression of matrix remodeling genes including TGF-beta1. Collectively, these findings indicated that leptin and its functional receptors (Ob-Rb) play a pivotal role in profibrogenic responses in the liver.

Hepatic stimulator substance activity in animal model of fulminant hepatic failure and encephalopathy.

Hepatic stimulator substance (HSS) is a known liver-specific but species-nonspecific growth factor. In the present study we examined the activity of the endogenously produced HSS in an established experimental model of fulminant hepatic failure (FHF) and encephalopathy, induced by repeated injections of thioacetamide (TAA). FHF was induced by three consecutive intraperitoneal injections of TAA (400 mg/kg body weight) in rats, at time intervals of 24 hr. The animals were killed at 0, 6, 12, or 18 hr following the last injection of TAA. The rate of tritiated thymidine incorporation into hepatic DNA, the enzymatic activity of liver thymidine kinase (EC 2.7.1.21), and the assessment of mitotic index in hepatocytes were used to estimate liver regeneration. HSS extract obtained from the livers of TAA-treated rats, sacrificed at the above-mentioned time points was tested for its activity. Increased HSS activity was noted in all TAA-treated animals, presenting a peak at 12 hr following the third TAA dose, suggesting active participation of this growth factor in hepatocyte replication in this animal model of FHF and encephalopathy. It may also be suggested that up-regulation of HSS activity could be used in future as a therapeutic approach in FHF.

Attenuation by boron supplementation of the biochemical changes associated with thioacetamide‐induced hepatic lesions

AbstractAcute hepatic failure is a severe complication induced by certain chemicals, drugs, or virus. Thioacetamide generally has been used for the study of hepatic failure in experimental animal model. The present study was aimed at to examine the role of boron in the pathogenesis of acute hepatic failure in rats. A single intraperitoneal injection of thioacetamide produced severe liver injury, as manifested by elevation in serum aminotransferases, alkaline phosphatase, and hepatic lipid peroxidation. Boron, when administered in the form of boric acid for three consecutive days followed by thioace‐tamide, attenuated thioacetamide‐mediated changes in the level of these biochemical parameters in a dose‐dependent manner. The effect of boron supplementation on the survival rates of rats treated with a lethal dose of thioacetamide was also determined and found to lower the mortality rates in the group of animals supplemented with boron followed by thioacetmide. The effects on biochemical parameters and the survival rates were dependent on the dose of boron administered as boric acid. It is concluded that boron provides protection against the thioacetamide‐induced acute hepatic failure in rats in a dose‐dependent manner. J. Trace Elem. Exp. Med. 15: 47–55, 2002. © 2002 Wiley‐Liss, Inc.

Pyrrolidine dithiocarbamate protects against thioacetamide-induced fulminant hepatic failure in rats

Background/Aims : Reactive oxygen species and nuclear factor kappa B (NF- κB) activation have been implicated in the pathogenesis of cell injury in experimental models of liver damage. The aim of the present study was to examine whether pyrrolidine dithiocarbamate (PDTC), an anti oxidant and inhibitor of NF- κB activation, would prevent hepatic damage induced in a rat model of thioacetamide (TAA)-induced liver failure. Methods : Fulminant hepatic failure was induced in the control and treatment groups by two intraperitoneal injections of TAA (either 300 or 400 mg/kg) at 24-h intervals. In the treatment groups, rats were treated also with PDTC (60 mg/kg/24 h, i.p.), initiated 24 h prior to TAA. Results : Liver enzymes, blood ammonia, and hepatic levels of thiobarbituric acid reactive substances ( P <0.001) and protein carbonyls ( P <0.05) were significantly lower in rats treated with PDTC compared to TAA only. Liver histology and the survival rate in the PDTC-treated rats were also improved ( P <0.01 compared to TAA only). NF- κB activation, 2 and 6 h after TAA administration, was inhibited by PDTC. Conclusions : In a rat model of fulminant hepatic failure, the administration of PDTC attenuated liver damage and improved survival. This effect may be due to decreased oxidative stress and inhibition of NF- κB activation.

Detrimental effects of nitric oxide inhibition on hepatic encephalopathy in rats with thioacetamide-induced fulminant hepatic failure.

Hepatic encephalopathy is a complex neuropsychiatric syndrome seen secondary to acute liver failure, chronic parenchymal liver disease, or portal-systemic anastomosis. Vasodilatation induced by nitric oxide (NO) may be involved in the development of hepatic coma. However, there are no comprehensive data concerning the effects of NO inhibition on the severity of hepatic encephalopathy. Male Sprague-Dawley rats weighing 300-350 g were used. Fulminant hepatic failure was induced by intraperitoneal injection of thioacetamide (TAA, 350 mg kg-1 day-1) for 3 days. Rats were divided into two groups to receive either NG-nitro-L-arginine methyl ester (L-NAME, 20 mg kg-1 day-1 via intragastric gavage) or normal saline (N/S) from 2 days prior to TAA administration for 5 days. Severity of encephalopathy was assessed by counts of motor activity and neurobehaviour test scores. Plasma levels of endotoxin, tumour necrosis factor-alpha and nitrate/nitrite were determined by the chromogenic Limulus assay, enzyme-linked immunosorbent assay and colorimetric assay, respectively. Compared with N/S-treated rats, the mortality rate was significantly higher in rats receiving L-NAME (59% vs. 18%, P < 0.01). Inhibition of NO had detrimental effects on the counts of motor activities (P < 0.05) and neurobehaviour score (P < 0.01). Rats treated with L-NAME had significantly higher plasma levels of endotoxin (26.7 +/- 3.8 pg mL-1) and tumour necrosis factor-alpha (29.4 +/- 6.5 pg mL-1) compared with rats treated with N/S (13.2 +/- 2.7 pg mL-1 and 11.2 +/- 2.6 pg mL-1, respectively, P < 0.01). Plasma levels of endotoxin and tumour necrosis factor-alpha, but not of nitrate/nitrite, were significantly correlated with the severity of hepatic encephalopathy (P < 0.05). Chronic L-NAME administration had detrimental effects on the severity of encephalopathy in TAA-treated rats, suggesting a protective role of NO in the development of fulminant hepatic failure.

Extracellular concentrations of taurine, glutamate, and aspartate in the cerebral cortex of rats at the asymptomatic stage of thioacetamide-induced hepatic failure: modulation by ketamine anesthesia.

Subclinical hepatic encephalopathy (SHE) was produced in rats by two intraperitoneal injections of TAA at 24 h intervals and the animals were examined 21 days later. Concentrations of the neuroactive amino acids taurine (Tau), glutamate (Glu) and aspartate (Asp), were measured in the cerebral cortical microdialysates of thioacetamide (TAA)-treated and untreated control rats. During microdialysis some animals were awake while others were anesthetized with ketamine plus xylazine. There was no difference in the water content of cerebral cortical slices isolated from control and SHE rats, indicating a recovery from cerebral cortical edema that accompanies the acute, clinical phase of hepatic encephalopathy in this model. When microdialysis was carried out in awake rats, dialysate concentrations of all the three amino acids were 30% to 50% higher in SHE rats than in control rats. Ketamine anesthesia caused a 2.2% increase of water content of cerebral cortical slices and increased Asp, Glu, and Tau concentration in microdialysates of control rats. In SHE rats, ketamine anesthesia produced a similar degree of cerebral edema, however, it did not alter Asp and Glu concentrations in the microdialysates. These data may reflect on one hand a neuropathological process of excitotoxic neuronal damage related to increased Glu and Asp, on the other hand neuroprotection from neuronal swelling indicated by Tau redistribution in the cerebral cortex. The reduction of the effects of SHE on Glu and Asp content in ketamine-anesthesized rats is likely to be due to interference of ketamine with the NMDA receptor-mediated component of the SHE-evoked excitatory neurotransmitter efflux and/or reuptake of the two amino acids. By contrast, the SHE-related increase of Tau content was not affected by ketamine anesthesia, indicating that the mechanism(s) underlying SHE-evoked accumulation of Tau must be different from the mechanism causing release of excitatory amino acids. The results with ketamine advocate caution when using this anesthetic in studies employing the cerebral microdialysis technique for measurement of extracellular amino acids.

Optical Analysis of Cirrhotic Liver by Near Infrared Time-Resolved Spectroscopy

The severity of liver cirrhosis was related with the optical properties of liver tissue. Various grades of liver cirrhosis were produced in rats by intraperitoneal injection of thioacetamide (TAA) for different periods: 4 weeks, 8 weeks, 12 weeks, and 16 weeks. Optical properties of the liver, absorption coefficient (μa) and scattering coefficient (μs'), were measured by near-infrared time-resolved spectroscopy. Histological examination confirmed cirrhotic changes in the liver, which were more severe in rats with TAA administration for longer periods. The μa increased in 4- and 8-week rats, and then decreased in 12- and 16-week rats. The μa of blood-free liver decreased as liver cirrhosis progressed. The hemoglobin content in the liver calculated from the μa values increased in 4- and 8-week rats and decreased in 12- and 16-week rats. The μs' decreased in the cirrhotic liver, probably reflecting the decrease in the mitochondria content. It was shown that μa and μs' determination is useful to assess the severity of liver cirrhosis. © 1999 Society of Photo-Optical Instrumentation Engineers.

Hepatoprotective effect of the endothelin receptor antagonist TAK-044 against ischemia-reperfusion injury in the cirrhotic rat liver

We have previously demonstrated that a new endothelin ET A/ET B receptor antagonist, TAK-044, inhibits ischemia-reperfusion injury in canine normal livers. The present study was undertaken to investigate whether or not TAK-044 is effective to reduce the ischemia-induced injury in cirrhotic liver. Cirrhosis was induced by the intraperitoneal injection of thioacetamide (300 mg/kg body wt), twice a week for 10 weeks, into male Wistar rats. In the partial liver ischemic model (60 min) with or without cirrhosis, ischemia-reperfusion injury was compared between the TAK group with an intravenous injection of TAK-044 (1 and 3 mg/kg) prior to ischemia and the non-treated control group. The serum leaking liver enzymes reached their peaks at 6 h after recirculation and decreased thereafter in both normal and cirrhotic rats. Although the postreperfusion peaks of the enzymes were lower in the cirrhotic rats than in the normal ones, their peaks were significantly lower in the TAK group than those in the control group whatever the livers were normal or cirrhotic. The hepatocyte swelling and sinusoidal narrowing observed 1 h after reperfusion were significantly suppressed in the TAK group than in the control group. These were no differences between the low (1 mg/kg) and high dose (3 mg/kg) rats. These findings indicate that preischemic administration of TAK-044 is useful as a hepatoprotective agent in cirrhotic livers as well as in normal ones.

Different roles of free hydroxyl radicals, nitric oxide and tumor necrosis factor α in thioacetamide induced liver cirrhosis in rats

Reactive oxygen species, proinfiammatory cytokines, and nitric oxide have all been implicated in the pathogenesis of hepatic fibrosis. The aim of the present study was to examine the respective roles of these factors in the pathogenesis of thioacetamide-induced hepatic cirrhosis in rats. Methods: Liver cirrhosis was induced by intraperitoneal injections of thioacetamide (200 mg/kg) twice a week, for 12 weeks. Rats were treated concurrently with one of the following agents: the hydroxyl free radical scavenger, dimethylsulfoxide (DMSO, 4 g/kg, i.p. or p.o., 3 times a week), the anti tumor necrosis factor-~x agent pentoxifylline (PTX, 20, 100 and mg/kg, 3 times a week) or the nitric oxide synthase inhibitor N-mono-methyl arginine ester (L-NAME) (0.1 mg/ml in the drinking water), given either alone or together with pentoxifylline 20 mg/kg. Results: The degree of liver fibrosis, spleen weights and hepatic hydroxyproline levels were determined after 12 weeks in the different treatment groups, and shown in the Table:

Natural protoberberine alkaloids from Enantia chlorantha, palmatine, columbamine and jatrorrhizine for thioacetamide-traumatized rat liver.

Experimental liver injury was provoked experimentally in rats with intraperitoneal injections of thioacetamide. Traumatized rats received further intraperitoneal injections of Hepasor, a protoberberine alkaloid extract from Enantia chlorantha (Annonaceae) containing palmatine, columbamine and jatrorrhizine. The development of body weight was kept under continuous control. Biochemical assays of blood plasma, serum alanine transferase (S-ALT), serum alkaline phosphatase (S-AP), serum creatinine S-CREAT, serum hydroxyproline (S-OH-PROL) and serum calcium (S-Ca) were done and liver samples for histological processing were taken. The biochemical results obtained indicate Hepasor exerted a marked influence on the S-ALT activities and S-OH-PROL values in female rats, but more incidental one in male rats. Some reduction in S-AP activity and S-CREAT values, which was also dependent on sex, was also found. The histological findings in the liver sections of female rats show that Hepasor improves the blood flow and mitotic activity in thioacetamide-traumatized livers.