MATERIALS AND METHODS

Experimental design. From our previous study, the critical preser-vation times for livers stored in normal saline with 2 mM calcium chloride at 4 C were determined to be 4 hr and 8 hr, respectively, and at 37 C, 1 hr and 2 hr (5). To determine if preservation in the cold resulted in microcirculatory injury of potential importance in graft survival, livers were stored by the same techniques and for the same times as above, then fixed at physiological perfusion pressures and examined by light and electron microscopy. Having identified the morphological features of cold preservation injury in this model, we examined a different model at its critical times, that of Tamaki et al.(6), which used a different preservation solution and different strain of rat. The conditions used for studies with the model used by Tamaki et al. were as described elsewhere (6). Experimental groups. Fifteen male Wistar rats (200–250 g) were used for the initial study. Rats were anesthetized using isofluorane and then underwent midline laparotomy. Donor hepatectomy was performed using the technique described by Kamada and Calne (7). The infrahe-patic vena cava was dissected free and the right renal vein was ligated. The falciform ligament was divided and the left phrenic vein tied proximally. The lobes of the liver were freed of all peritoneal attach-ments and all collateral circulation to the liver was interrupted. The bile duct was severed near the entry to the pancreas and the major branches of the portal vein divided. Animals were anticoagulated with 500 units of heparin given iv prior to ligation of the hepatic artery. The portal vein was flushed through a venotomy using 0.9% NaCl and 2 mM CaCl, at 4 C while dividing the suprahepatic vena cava in the mediastinum. During flushing, the perfusion pressure was never greater than 15 cm water. A total of 32 ml of solution was used. After flushing, a 1.2 cm length of Teflon tubing, bevelled at the ends, was inserted through the portal vein venotomy site. The liver was then excised and immersed in the storage solution of identical composition to the flush-ing solution. It was flushed once again with 10 ml of the flush solution until the effluent was free of blood. Livers to be preserved at 37 C were treated in identical fashion except that the temperature of the flushing solution was 37 C.