The effect of hepatectomy on the energy state and on acid-base variables of the rat brain

Hyperammonemia and chronic hepatic encephalopathy: an in vivo PMRS study of the rat brain

The brain energy metabolism of rats affected by chronic hepatic encephalopathy due to portacaval shunting was monitored by in vivo 31P-nuclear magnetic resonance spectroscopy before and after ammonium acetate administration. With respect to healthy unoperated and to sham operated controls, portacaval shunting decreased the levels of the nuclear magnetic resonance (NMR) visible brain phosphocreatine and nucleoside phosphates, and the intracellular [free Mg(2+)]. Ammonium acetate induced a further decrease of the levels of the NMR detectable phosphocreatine and nucleoside triphosphates and of the [free Mg(2+)], while the PMR spectra of the brain of non-shunted rats did not show any significant change even after treatment with ammonium acetate.

A simple experimental model of total hepatectomy, hepatic ischemia and extrahepatic portal obstruction in rats using splenic transposition

The objective of this study was to develop an easy and simple experimental rat model of total hepatectomy, hepatic ischemia and extrahepatic portal obstruction. The first operation involved transposing the spleen with its scarified capsule in a subcutaneous pouch to produce portasystemic anastomosis. Total hepatectomy was easily performed in a lobe-by-lobe fashion 2 weeks following the first stage operation. Anhepatic rats receiving a glucose infusion survived for about 10 hours and all died of acute hepatic failure. Hepatic support systems can be accurately evaluated in this anhepatic rat model because of its uniformity. Sixty minutes of hepatic ischemia was able to be performed in rats with a transposed spleen for a portasystemic shunt and no complicated or technically involved procedure was required for the ischemic model. No rats died due to technical difficulties, suggesting the reliability and reproducibility of this ischemic model. An animal model resembling extrahepatic portal vein obstruction was also obtained by ligation of the portal vein; a simple maneuver which was able to produce collateral veins to the liver and cavernous transformation, as similarly seen in clinical patients with extrahepatic portal obstruction. Because these 3 animal models were so easily achieved in the rat, and since the changes in hepatic function and formation of the collaterals to the liver after portal vein occlusion are still poorly understood, this model should prove valuable for future study.

Determination of free tryptophan in plasma and its clinical applications

Free tryptophan in plasma was separated by centrifugation through an Amicon ultrafiltration membrane cone. The value obtained without control of pH was found to be lower than that obtained with control of pH by an improved method ( Hijikata et al. (1981) Anal. Biochem. 118, 10-16). For determination of the total tryptophan concentration in the plasma, high performance liquid chromatography (HPLC) was better than the method of Denckla Dewey as modified by Bloxam & Warren ( (1974) Anal. Biochem. 60, 621-625), as judged on the basis of sensitivity, recovery rate and coefficient of variance. The total tryptophan concentration in the plasma determined by HPLC was lower than that determined by the Bloxam & Warren method. The total tryptophan concentration (t-Trp), free tryptophan concentration (f-Trp) and f-Trp/t-Trp ratio were 55.8 +/- 10.2 mumol/l, 11.6 +/- 1.5 mumol/l and 0.211 +/- 0.03 (mean +/- 1 SD) respectively, in healthy subjects (controls). No significant difference was observed between the values of controls and those of patients with liver cirrhosis, hepatocellular carcinoma, liver cirrhosis with hepatocellular carcinoma and hepatic encephalopathy of liver cirrhosis without bleeding. But in liver cirrhosis with bleeding, free tryptophan concentration (f-Trp, 48.0 +/- 23.3 mumol/l, p less than 0.001) and f-Trp/t-Trp ratio (0.645 +/- 0.289, p less than 0.001) were significantly higher than those of controls.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of total hepatectomy on cerebral energy state, ammonia-related amino acids of the brain and plasma amino acids in the rat

The influence of total hepatectomy on cerebral energy state, ammonia-related amino acids of the brain tissue and plasma amino acids was studied in anaesthetized rats after total hepatectomy. The hepatectomy was performed with the aid of a microsurgical three-stage procedure. In the first stage, division of the inferior vena cava was performed. In the second stage 4 weeks later a porta-caval anastomosis was constructed, followed after 1 week by a total hepatectomy. The brain energy state, defined as the concentrations of phosphocreatine, ATP, ADP and AMP, was unchanged 4 h after the hepatectomy. Plasma amino acids did not differ significantly between hepatectomized and shunted control rats. On the other hand, clear-cut increases in the concentrations of glutamine, and decreases in the concentrations of glutamate and aspartate, were observed in the fronto-parietal part of the cerebral cortex and the brain stem. These changes might explain the minor manifestations of cerebral dysfunction in the early phase of the hepatectomized state.

Combined or individual administration of branched-chain amino acids following total hepatectomy in the rat: effects on amino acids and indoleamines in brain

The effects of infusing leucine, isoleucine, and valine, either singly or together into rats after total hepatectomy were compared. Hepatectomized rats receiving only glucose had high concentrations in plasma of most amino acids, except the branched-chain amino acids; in brain, the concentrations of glutamine, most large neutral amino acids and 5-hydroxyindoleacetic acid were greatly elevated. When all three branched-chain amino acids were infused, the rise in plasma concentration of essential amino acids and tyrosine was significantly reduced. Infusion of isoleucine did not significantly reduce the concentrations of any essential amino acid in plasma while valine reduced lysine, methionine and tryptophan and leucine reduced only methionine. In contrast, all infusions of branched-chain amino acids, either singly or in combination, reduced brain levels of other large neutral amino acids. Infusion of branched-chain amino acids greatly elevated the plasma concentrations of glutamine and alanine and prevented the decrease in brain concentrations of glutamic acid, a neurotransmitter.

Metabolism of acetate to amino acids in brains of rats after complete hepatectomy

The concentration of glutamine increases in the brain after hepatectomy. In the present studies the conversion of intravenously given [14C]acetate to [14C]glutamate and [14C]glutamine was studied in control rats and in rats at 6 h after complete hepatectomy. The incorporation of label into glutamate was only slightly inhibited, but the further incorporation into glutamine was greatly inhibited, after hepatectomy. These data, and previous data using [14C]glucose as precursor, indicate that synthesis of glutamine in brain is inhibited after hepatectomy, and suggest that its concentration must increase because degradation is inhibited to an even greater extent.