Dynamic measurement of metabolic function in the rat liver: an application of reverse microdialysis.

Background: Traditional markers of liver function and microsomal activity tests require regular samplings and tissue removal. The microdialysis technique is a promising tool for pharmacokinetic study without the need for actually removing samples of those tissues and fluids. We verified the possibility of using reverse microdialysis for dynamic monitoring of hepatic metabolic function.

Methods: Adult male Sprague-Dawley rats were used and anesthetized using pentobarbital sodium. Reverse microdialysis was done by implanting a microdialysis probe into the middle lobe of the liver; the probe was then perfused with a lidocaine-containing solution. Concentrations of lidocaine and its major metabolite, monoethylglycinexylidide (MEGX), were measured in the dialysate. Metabolic ability was assessed by dividing the MEGX production by lidocaine administration. Hepatic ischemia-reperfusion and liver cirrhosis models were used to verify its application in dynamic measurement of liver metabolic function.

Results: The implantable microdialysis probe had stable contact with the liver tissue. In normal rats, 4.73 +/- 0.41% of the lidocaine was transformed to MEGX in 20 min. Only 16% of this value was preserved in cirrhotic animals. Hepatic ischemia for 20 min transiently depressed the MEGX formation and did not cause further injury after reperfusion.

Conclusion: We confirmed the ability of an implantable microdialysis probe to be in constant contact with the liver tissue and thus deliver a stable transmission of chemicals across a microdialysis membrane for a certain period of time. We also verified the feasibility of reverse microdialysis as a tool for the dynamic measurement of hepatic metabolic function.