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Method Article
* These authors contributed equally
This protocol describes a common and feasible method of inducing acute liver injury (ALI) via CCl4 exposure through an orogastric tube. CCl4 exposure induces ALI through the formation of reactive oxygen species during its biotransformation in the liver. This method is used to analyze the pathophysiology of ALI and examine different hepatoprotective strategies.
Acute liver injury (ALI) plays a crucial role in the development of hepatic failure, which is characterized by severe liver dysfunction including complications such as hepatic encephalopathy and impaired protein synthesis. Appropriate animal models are vital to test the mechanism and pathophysiology of ALI and investigate different hepatoprotective strategies. Due to its ability to perform chemical transformations, carbon tetrachloride (CCl4) is widely used in the liver to induce ALI through the formation of reactive oxygen species. CCl4 exposure can be performed intraperitoneally, by inhalation, or through a nasogastric or orogastric tube. Here, we describe a rodent model, in which ALI is induced by CCl4 exposure through an orogastric tube. This method is inexpensive, easily performed, and has minimal hazard risk. The model is highly reproducible and can be widely used to determine the efficacy of potential hepatoprotective strategies and assess markers of liver injury.
The frequency of toxic insults to the liver, especially due to alcohol and drug abuse, is increasing. Acute liver injury (ALI) is associated with high mortality rates and has caused clinical concerns1,2. Toxic injury leads to death signaling pathways in the liver, resulting in hepatocyte apoptosis, necrosis, or pyroptosis. ALI plays a crucial role in the development of hepatic failure, which is characterized by severe liver dysfunction including complications such as hepatic encephalopathy and impaired protein synthesis3,4. Although recent research has increased our knowledge about the physiological and pathological changes accompanying hepatic failure, it has not completely explained the pathomolecular features that affect the mechanisms of cell death. Furthermore, no medications are currently available to reverse the progressive deterioration in ALI patients. Currently, the only significantly effective treatment is liver transplantation5,6.
In order to investigate the mechanism and pathophysiology of ALI and to test different hepatoprotective strategies, different animal models are used to induce ALI. A preferable animal model of ALI should mimic the pathological process of the disease via a reliable, validated, inexpensive and easy to apply method. Examples of experimental models include hepatotoxic agents, surgical procedures such as total or partial hepatectomy, complete or transient devascularization, and infective procedures7,8,9. Known hepatotoxic substances include galactosamine, acetaminophen, thioacetamide, azoxymethane and CCl4. Of these, CCl4 is widely used although it has not yet been well characterized10,11,12,13.
CCl4 is an organic colorless liquid compound with a sweet smell and almost no flammability at lower temperatures. Exposure to high concentrations of CCl4 can cause damage to the central nervous system, including deterioration of the liver and kidneys. CCl4 induces ALI through its biotransformation in the liver, which forms reactive oxygen species. This occurs via the P450 cytochrome enzyme 2E1, forming an active metabolite and resulting in cell damage by macromolecule binding, enhancement of lipid peroxidation and disturbance of intracellular calcium homeostasis14. In addition, the CCl4 model can be used to stimulate the astrocytes at the level of RNA synthesis15. This hepatotoxin has been administered by the intraperitoneal, intraportal, oral, and intragastric routes16.
In this protocol, we describe in detail CCl4-induced ALI in rats via an orogastric tube. This method induces robust and reproducible ALI that can be used to investigate the pathogenesis of ALI. Determination of liver disease severity is monitored by measurement of serum glutamate-pyruvate transaminase (GPT), glutamic oxaloacetic transaminase (GOT) enzymes and total bilirubin (TB) as well as definitive histological diagnosis by hematoxylin and eosin (H&E) stained liver tissues. Exposure to CCl4 through an intragastric access allows for a practical, inexpensive, minimally invasive method with minimal hazard risk.
The experiments were conducted according to the recommendations of the Declarations of Helsinki and Tokyo and to the Guidelines for the Use of Experimental Animals of the European Community. The experiments were approved by the Animal Care Committee of Ben-Gurion University of the Negev.
NOTE: The CCl4 model has been generated and used in a previous study17. The protocol timeline is demonstrated in Table 1.
1. Preparing rats for the experimental procedure
NOTE: Select adult male Sprague Dawley rats weighing 300−350 g.
2. Determination of serum GOT, GPT, and TB baseline levels
3. Induction of acute liver injury in rats
CAUTION: Exposure to high concentrations of CCl4, including absorption through vapor or skin, can have negative effects on the central nervous system and cause degeneration of the liver and kidneys. Prolonged exposure can cause coma or death.
4. Determination of serum GOT, GPT, and TB levels after 24 h
5. Liver collection for histological examination
6. Histological examination
The TB, GOT, and GPT levels significantly increased 24 h after inducing ALI (more at higher CCl4 doses) compared to sham-operated controls (p < 0.001) (Figure 1). The levels of TB, GOT, and GPT at baseline were normal and were not significantly different than sham-operated controls. At 24 h, all three interventional groups, 1 mL/kg CCl4 (1, 1−2), 2.5 mL/kg CCl4 (3, 3−4), and 5 mL/kg CCl4 (4, 4−5.75), had a significantly higher...
In this protocol, CCl4 is used as a liver toxin to induce ALI in rats. ALI is characterized by loss of hepatic parenchyma and subsequent dysregulation of the liver’s metabolic and synthetic functions. Drugs, viruses, toxins, autoimmune diseases, metabolic diseases, and vascular disorders all induce hepatocyte death, and the subsequent inflammatory response contributes to the pathogenesis of ALI.
The initial insult to the liver leads to cytokine production, chemokine release, a...
The authors have nothing to disclose.
The authors gratefully acknowledge Bertha Delgado, Department of Pathology, Soroka Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, for her help in the laboratory as well as in the histology analysis.
Name | Company | Catalog Number | Comments |
22 G catheter BD Neoflon TM | Becton Dickinson Infusion Therapy AB | ||
4% buffered formaldehyde solution | Sigma - Aldrich lab materials technologies | ||
BD Microtainer SST TM Tubes | Becton Dickinson and Company | ||
Carbone tetrachloride | Sigma - Aldrich lab materials technologies | CAS 56-23-5 | |
Isofluran, USP 100% | Piramamal Critical Care, Inc | ||
Olympus AU2700 Chemistry-Immuno Analyzer | Olympus (MN, USA) | Analysis of blood samples was done by the fluorescence method | |
Olympus BX 40 microscope | Olympus | ||
RAT Feeding Needles | ORCHID SCIENTIFICS | ||
SYRINGE SET 1 and 2 ml MEDI -PLUS | Shandong Zibo Shanchuan Medical Instruments Co., Ltd |
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