AN OPTIMIZED MODEL FOR RAT-LIVER PERFUSION STUDIES

Conditions which influence the viability, integrity, and extraction ef ficiency of the isolated perfused rat liver were examined to establish optimal conditions for subsequent work in reperfusion injury studies including the choice of buffer, use of oncotic agents, hematocrit, per fusion flow rate, and pressure. Rat livers were perfused with MOPS-buf fered Ringer solution with or without erythrocytes. Perfusates were co llected and analyzed for blood gases, electrolytes, enzymes, radioacti vity in MID studies, and lignocaine in extraction studies. Liver tissu e was sampled for histological examinations, and wet:dry weight of the liver was also determined. MOPS-buffered Ringer solution was found to be superior to Krebs bicarbonate buffer, in terms of pH control and b uffering capacity, especially during any prolonged period of liver per fusion. A pH of 7.2 is chosen for perfusion since this is the physiolo gical pH of the portal blood. The presence of albumin was important as an oncotic agent, particularly when erythrocytes were used in the per fusate. Perfusion pressure, resistance, and vascular volume are how-de pendent and the inclusion of erythrocytes in the perfusate substantial ly altered the flow characteristics for perfusion pressure and resista nce but not vascular volume. Lignocaine extraction was relatively flow -independent. Perfusion injury as defined by enzyme release and tissue fine structure was closely related to the supply of O-2. The optimal conditions for liver perfusion depend upon an adequate supply of oxyge n. This can be achieved by using either erythrocyte-free perfusate at a how rate greater than 6 ml/min/g liver or a 20% erythrocyte-containi ng perfusate at 2 ml/min/g. (C) 1996 Academic Press, Inc.