Critical preservation injury in rat fatty liver is to hepatocytes, not sinusoidal lining cells

Fatty livers are more prone to primary nonfunction after transplantation. We hypothesized that sinusoidal lining cells (SLCs) in fatty livers of obese Zucker rats are more susceptible to ischemia/reperfusion injury than in normal livers.

Cold University of Wisconsin solution-preserved (30 min or 24 hr) livers from obese and lean Zucker rats were perfused ex vivo for 90 min with oxygenated warm acellular buffer containing hyaluronate. Bile output, alanine transferase, and hyaluronate clearance were measured during reperfusion. Trypan blue was infused at completion of reperfusion to assess cell membrane integrity. Another group of 24-hr preserved livers were reperfused with cold hypoxic buffer to differentiate the effects of preservation from reoxygenation.

After 30 min of preservation, fatty livers had significantly decreased flow (1.9 vs. 2.6 ml/g/min), increased resistance, decreased hyaluronate clearance (17 vs. 35 microg/g liver) and lower bile output (13 vs. 42 microl/g) in comparison with normal livers. Hepatocyte and SLC trypan blue uptake were minimal and similar in both groups. After 24 hr of preservation, flow (2.0 vs. 2.0), resistance, hyaluronate clearance, and bile output were similar in both fatty and normal livers. The SLC trypan blue uptake was increased but similar in both groups (22 vs. 20%). In contrast, a significantly greater number of hepatocytes were trypan blue-stained in fatty livers (32 vs. 0.6%), accompanied by a marked increase in lactate dehydrogenase and alanine transferase release. Hypoxic reperfusion caused a significant decrease in hepatocyte and SLC trypan blue uptake.

Fatty livers demonstrate impaired hepatocyte and SLC function, after even a very brief preservation. With increasing preservation, hepatocytes appear to be more susceptible to injury than SLCs. Reoxygenation appears to be important in triggering this event.