For years, the isolated perfused rodent liver (IPRL) model has been used to investigate the physiology and pathophysiology of the liver. First reported by Claude Bernard in 1855, the technique has remained a reliable and popular reperfusion model for a range of application areas such as:
- Liver role studies
- Liver relationship to insulin and hormonal regulation
- Liver damage assessment
- Liver preservation and transplantation studies
- Study of liver diseases: Hepatitis, Cirrhosis, Liver cancer, Liver failure
So for those of you interested in using the IPRL model in your lab, or if you’re just wanting to know a bit more about the technique, we have created a short guide on things to consider before carrying out an isolated perfused liver experiment using one of our Isolated Perfused Rodent Liver Foundation Systems.
A standardized IPRL set-up (Rat Model)
1. Perfusate type and volume
When choosing what reperfusion medium to use in your IPRL system, there are a few things to consider. Ideally, the perfusate will mimic the role of blood, providing oxygen and energy to your liver as well as ‘removing’ any unwanted waste products.
Most perfusates should have a buffering capacity, energy source, oncotic pressure capacity, and an oxygen-carrying capability.
The preferred perfusion solution for an IPRL preparation is Krebs–Henseleit Buffer without albumin, containing 10mM glucose as an energy source and bicarbonate-carbon dioxide as a buffering agent. As it is protein-free perfusate, some may choose to add bovine serum albumin to increase the oncotic pressure of the perfusate closer to physiological levels, however, it has been shown to cause problems with foaming during reperfusion and is potentially damaging to the hepatocytes.
The volume of the perfusate will also influence the concentration of perfusate elements. Most volumes range from 150-500 cm3, depending on the perfusion circuit. While there seems to be no ‘stock standard’ volume to use, it’s worth taking the time to think about as a larger volume may affect the detection limit of elements you are wanting to measure in your perfusate.
2. Perfusion pressure and flow
The perfusion pressure and flow are generally dependent on the perfusion type. The typical standard technique involves single cannulation and perfusion of the Portal Vein (inlet), Caval Vein or Suprahepatic Vena Cava (outlet) with the pressure maintained ~15 mmHg and a perfusion flow of 3 mL/min/g liver weight (for a rat liver weighing 4–5 g). The Bile Duct is also cannulated for the removal of bile samples.
Pro Tip: Your flow should never exceed 5ml/min/g liver weight, or you risk damaging the sinusoidal endothelial cell lining. On the other hand, if the pressure is too low, large areas of the liver may not be perfused properly.
Some setups may involve dual perfusion of the liver; perfusing the Portal Vein and Hepatic/Coeliac Artery. This technique is useful when looking at bile flow and transport, as well as studies looking at hepatic flow.
The pressure and flow of an IPRL system can be easily monitored using pressure transducers (included in the Apparatus) and the Isolated Liver Volume Flow Kit using in-line transonic flow sensors. If required, higher resolution pressure transducers are also available for purchase separately.
3. Perfusion temperature
For an IPRL set-up, it’s important to maintain the perfusate at physiological temperature (37°C), as even small deviations can have substantial effects on the liver, ultimately affecting your experimental results.
Our Isolated Perfusion Temperature & pH Kit is the perfect solution for maintaining the optimal temperature in your circuit. The T-type Pod and T-type Implantable Thermocouple Probe (IT-18) continuously monitor the temperature of the perfusate, while the Radnoti thermal circulator/bath heats and maintains the perfusate temperature.
Pro Tip: By measuring the temperature at the site of inflow, you can avoid potential damage to the liver parenchyma with the temperature probe.
4. Perfusion duration and pH
Keep in mind that over time, the H+ buffering capacity, and energy sources of your perfusate will dwindle. If left uncorrected, the perfusate will become acidic due to anaerobic glycolysis and leakage of lytic enzymes, damaging the liver.
Using our Isolated Perfusion Temp and pH kit you can monitor the pH of the perfusate within our analysis software LabChart, giving you an indication of the 'quality' of the perfusate through the duration of the experiment.
Inadequate oxygenation of the isolated liver will lead to anaerobic glycolysis and intracellular acidosis - damaging the liver tissue. A typical IPRL set-up will maintain continuous oxygenation of the perfusate at >500 mmHg using an oxygenator (95% oxygen and 5% carbon dioxide).
The perfusate is then circulated through the liver at a rate of 3 ml/min/g liver weight (as mentioned above), ensuring that the net supply of oxygen molecules to the parenchyma is sufficient, preventing damage to the tissue.
Our IPRL solutions:
Isolated Perfused Rodent Liver Foundation System
A foundation system that provides the glassware for perfusing an isolated rodent liver to maintain its hepatic function. It has acquisition hardware and software for data collection and analysis, including pressure, flow, and temperature.
Radnoti Isolated Rodent Liver/Kidney Apparatus
Already have a PowerLab and LabChart? Then this is the solution for you! A glass apparatus designed to maintain the function of an isolated rodent (mouse or rat) liver or kidney preparation, and measure up to two perfusion pressures in the perfusion circuit.
Add on Kits and accessories (purchased separately):
- Isolated Perfusion Temperature & pH Kit
- Isolated Perfusion O2 & CO2 Kit
- Isolated Liver Volume Flow Kit
- Bridge Amp
- In-vitro Liver/Kidney Perfusion Chamber
Bessems M et al. 2006, The isolated perfused rat liver: standardization of a time-honoured model, Laboratory Animals.
Daughaday WH et al. 1976, The Effects of Insulin and Growth Hormone on the Release of Somatomedin by the Isolated Rat Liver, Endocrinology.
Jaeschke H, Smith CV & Mitchell JR 1988, Reactive oxygen species during ischemia-reflow injury in isolated perfused rat liver, The Journal of Clinical Investigation.
Mehvar R & Zhang X 2002, Development and Application of an Isolated Perfused Rat Liver Model to Study Stimulation and Inhibition of Tumor Necrosis Factor-α Production ex Vivo, Pharmaceutical Research.
Parasrampuria R & Mehvar R 2010, Dose-Dependent Inhibition of Transporter-Mediated Hepatic Uptake and Biliary Excretion of Methotrexate by Cyclosporine A in an Isolated Perfused Rat Liver Model, Journal Of Pharmaceutical Sciences.