MATERIALS AND METHODS

Sprague-Dawley rats weighing between 200 and 250 g after an overnight fast were anesthetized with intraperitoneal pentobarbital(3 mg/lOO g body wt). The bile duct and portal vein were cannulated in situ, and an in-fusion with oxygenated Krebs-Ringer bicarbonate buffer ww(25) containing glucose in the same concentration as the initial medium was immediately started. The liver was then excised from the animal, adherent tissue trimmed away, and the two small accessory lobes removed for glycogen determination. Immediately after the biopsy, the portal vein cannula was occluded with a hemostat and the liver transferred to the perfusion apparatus. The transfer process took lo-15 set during which the liver was deprived of 02. During the operative period, flow rate averaged about 15-20 ml/min, except during the period when the liver was trimmed and the biopsy taken when it was slower because of the manipulation. The perfusion apparatus was a modification of the one described by Miller (28). Livers were cyclically perfused with 90-100 ml of a medium composed of KRB which contained per 100 ml: 4 g bovine serum albumin (Cohn fraction V, Armour Pharmaceutical, Kankakee, Ill.), 5 mgstreptomycin, 5 mg penicillin, 20 mg heparin, 1 millimole of alanine, 10-12.5 PC alanine-U-14C, and either 0, 150, or 300 mg of glucose. The medium had previouslv been passed through a Millipore filter with interstices of 0.45 p. Throughout the perfusion, it was exposed to a