Amino acid metabolism in the perfused rat liver

Abstract

A perfused organ should provide a useful tool for metabolic studies, especially for investigation of the significance in the metabolism of the whole organ of reactions known to occur in broken cell preparations. Perfusion of rat livers with saline solution through the vena cava has confirmed the importance ofpyruvate in transamination reactions (Bristow & Kerly, 1964) (1951). Unfortunately not only do Miller and his co-workers give insufficient information on some important experimental points (e.g. the method of filming the blood in the oxygenator), but they have varied the conditions, such as the composition of the perfusion medium, from one set of experiments to another. Other authors have introduced modifications so that experimental conditions have varied considerably and few studies, even from the same laboratory, are strictly comparable. Therefore before attempting a study of amino acid metabolism in livers perfused with blood it was necessary to develop a standard technique which would allow the liver to be maintained as nearly as possible in a normal physiological condition for several hours and then to investigate changes in amino acid composition of liver, perfusion medium and bile under basal conditions. The results of this investigation are described below.

Glycoprotein synthesis by the perfused livers from normal and tumour-bearing rats.

“…The various parameters measured on each sample are shown in Table I. The results for normal liver perfused with normal blood agree generally with those published by other workers (Cohen and Gordon, 1958;Fisher and 1964). When the three perfusion systems are compared, however, some variations are seen.…”

“…The portal vein was tied off and cannulated, the thorax quickly opened and the right auricle pierced. Perfusion was then commenced with Ringers solution containing 5 % blood (Fisher and Kerly, 1964), the perfusate running to waste. With this technique the flow through the liver was only stopped for 1-5-2 minutes.…”

Effects of a short-term fast on albumin synthesis studied in vivo, in the perfused liver, and on amino acid incorporation by hepatic microsomes

“…The liver was then removed and mounted on a platform in an humidified box maintained at 37'C. The perfusate in all studies consisted of two parts of fresh heparinized rabbit blood; one part oxygenated Krebs-Hensleit solution which contained 50-90 mg/100 ml of glucose; 3-4 Amoles of amino acids/ml, equivalent to fresh plasma, which included the essential amino acids; and 0.69 umole of L-glutamine/ml and 0.24 /Amole of L-arginine/ml were added (16). Perfusion was directed into the portal vein at a rate of 0.3-1.4 ml/g of liver per min.…”

Effects of intrabrachial arterial infusion of pyruvate on forearm tissue metabolism

“…Terminal oxidation of amino acids by muscle has been demonstrated in vitro (35)(36)(37). Valine, leucine, and isoleucine are of special interest because hepatic uptake is small (38)(39)(40) and extrahepatic tissues are thought to be the major site of oxidation (41). In the present investigation decreased release of branched chain amino acids was associated with increased alanine release during the high dose pyruvate infusion.…”