Increase in the content of quinolinic acid in cerebrospinal fluid and frontal cortex of patients with hepatic failure

Quinolinic acid (QUIN), an excitotoxic tryptophan metabolite, has been identified and measured in human cerebrospinal fluid (CSF) using a mass-fragmentographic method. Furthermore, its content has been evaluated in frontal cortex obtained at autopsy from the cadavers of patients who died after hepatic coma. During the coma, the concentration of QUIN in the CSF was 152 +/- 38 pmol ml-1. In contrast, the concentration in control patients affected by different pathologies was 22 +/- 7 pmol ml-1. In the frontal cortex of patients who died after episodes of hepatic encephalopathy, the content of QUIN was three times higher than in controls (2.6 +/- 0.6 versus 0.80 +/- 0.08 nmol/g wet weight). As a result of these investigations we are now able to extend our previous observations on the increase of QUIN in the brains of rats used as experimental models of hepatic encephalopathy to man. QUIN should therefore be added to the list of compounds possibly involved in the pathogenesis and symptomatology of brain disorders associated with liver failure.

Cerebrospinal fluid gamma-aminobutyric acid levels in dogs with chronic portosystemic encephalopathy

Cerebrospinal fluid (CSF) gamma-aminobutyric acid (GABA) levels were measured in a dog model of spontaneous chronic portosystemic encephalopathy. Dogs with congenital portacaval shunts (intra- or extra-hepatic) develop neurological features of abnormal psychomotor behaviour and depressed consciousness that are consistent with the symptoms of chronic portosystemic encephalopathy in humans. In the five dogs studied, plasma ammonia was elevated, as was CSF tryptophan, both usual biochemical abnormalities in portosystemic encephalopathy. CSF levels of GABA in five dogs with portosystemic encephalopathy (100 +/- 13 pmol/ml) were not significantly different from those in five control dogs (96 +/- 14 pmol/ml). CSF levels of GABA were not altered after ammonia infusion. If enhanced GABA-ergic neurotransmission, due to influx of gut-derived GABA into the brain, is responsible for the pathophysiology of chronic portosystemic encephalopathy in this model, it is not reflected by increased levels of GABA in CSF.

Glutamic acid and glutamine levels in serum and cerebrospinal fluid in hepatic encephalopathy

Significant elevation of glutamic acid and glutamine concentrations in CSF was observed in hepatic encephalopathic patients with fulminant hepatitis and liver cirrhosis. However, the ratios of CSF glutamic acid to CSF glutamine levels and of CSF to serum glutamic acid and glutamine levels were significantly higher only in cirrhotic patients with hepatic encephalopathy. CSF glutamine levels were positively correlated with blood ammonia and CSF tyrosine levels in cirrhotic patients. The results indicate that CSF glutamic acid and glutamine levels are important tools in diagnosing hepatic encephalopathy in severe liver disease.

Amino acid, ammonia and neurotransmitter concentrations in hepatic encephalopathy: serial analysis in plasma and cerebrospinal fluid during treatment with an adapted amino acid solution

We evaluated changes of advanced liver disease and hepatic encephalopathy on the concentrations of amino acids (AA) and ammonia in plasma and cerebrospinal fluid (CSF) and of the neurotransmitters norepinephrine, dopamine and 5-hydroxytryptamine (5-HT) as well as the 5-hydroxyindole acetic acid (5-HIAA) in CSF before and at the end of a 3-day period of treatment with infusions enriched with branched chain amino acids (BCAA). The subjects studied were 13 patients with alcoholic cirrhosis and hepatic encephalopathy stages 1-3 (n = 8) and stage 4 (n = 5). The patients in coma stages 1-3 recovered during the treatment (survivors), those in coma stage 4 died before the study period was finished (non-survivors). The data emerging from this study show: Alterations of AA concentrations are much more pronounced in the CSF than in the plasma. In the case of tryptophan the alterations in plasma and CSF were inverse. Before the treatment the CSF-plasma ratios of the concentrations of BCAA and aromatic amino acids (AAA) are increased reflecting an activated transport of both the BCAA and AAA through the blood-brain barrier. High dose BCAA nearly normalized CSF concentrations and CSF-plasma ratios of AAA assuming that the treatment brought about an effective competition of cerebral uptake between BCAA and AAA. The CSF concentrations of ammonia and glutamine decreased significantly during treatment while the plasma concentrations changed only moderately. As to the neurotransmitters, only the concentrations of 5-HT and its metabolite 5-HIAA correlated with the clinical picture and with the concentration of their precursor AA.(ABSTRACT TRUNCATED AT 250 WORDS)

Extra- and intracellular amino acids in the hippocampus during development of hepatic encephalopathy

Fulminant hepatic failure was induced in rabbits by intravenous administration of galactosamine hydrochloride. The animals were sacrificed after 45 h and the hippocampus analyzed for free amino acids. In addition, free amino acids were measured in plasma and in the extracellular fluid of the hippocampus 20, 30 and 45 h after galactosamine injection. The extracellular fluid compartment was analyzed by slow perfusion of a thin dialysis tube which was implanted in the hippocampus one day prior to galactosamine administration. The amino acid concentration in the extracellular fluid agreed fairly well with that of the cerebrospinal fluid in the control situation. During development of hepatic failure, the plasma concentration of all amino acids increased. The changes in extracellular amino acids were smaller, except for phosphoethanolamine and glutamate. The concentration ratio intra/extracellular amino acids decreased in the hippocampus for amino acids with a normally high concentration gradient.

Neurotransmitter modifications in human cerebrospinal fluid and serum during hepatic encephalopathy

The concentrations of catecholamines, serotonin, histamine and GABA as well as some of their precursors and metabolites were measured in the CSF and the serum of human patients at different grades of hepatic encephalopathy. In all grades the CSF concentrations of the neurotransmitters were much increased over control levels, while the amount of metabolites varied with the grade of coma. The data suggest modifications of the cerebral turnover of dopamine, norepinephrine and serotonin. The "false transmitters" also occurred in high concentration in all grades of hepatic coma and could play a role in the alterations of synaptic transmission. The present results suggest that the biochemical changes between grade 2 and grade 4 hepatic coma could be due to an inhibition of dopamine beta-hydroxylase. Moreover, the levels of neurotransmitter precursors, tyrosine and 5-hydroxytryptophan, showed enhancement in grades 2 and 3 followed by an important reduction in grade 4. Finally, it seems that the biogenic amines measured in the CSF are of central origin and that their quantification in human lumbar fluid gives new information on the central mechanisms involved in hepatic encephalopathy.

[Electroencephalography and cerebrospinal fluid glutamine in portal-systemic encephalopathies]

A group of patients with portal-systemic encephalopathy were studied. The conscious disturbances, eletroencephalographic findings and the spinal fluid glutamine levels were analyzed. Based on the results the authors concluded that the eletrencephalogram can be utilized for determination of the degree of hepatic coma and also for its prognostic valuation. In addition they found that monitorization of spinal fluid glutamine levels is the most important test for characterization of the degree of hepatic encephalopathy.

[Therapy of hepatic encephalopathy. Changes in the cerebrospinal fluid concentration of catecholamine neurotransmitters, ammonia and amino acids in the course of an infusion treatment with branched-chain amino acids]

Infusions containing branched-chain amino acids have recently been used for the therapy of hepatic coma. Their mode of action was attributed to a reduction in the intracerebral concentrations of the aromatic amino acids with resultant normalization of the neurotransmitters noradrenaline, dopamine and serotonin, synthesized from these amino acids. In order to further clarify this therapeutic mechanism an infusion solution consisting of branched-chain amino acids and ammonia-reducing amino acids was administered to patients with porto-systemic encephalopathy. The amino acid pattern, the ammonia in plasma and liquor, and the neurotransmitters noradrenaline, adrenaline and dopamine, in the liquor were determined before and after the course of treatment. Our studies show that the therapeutic effect of branched-chain amino acids in the therapy of hepatic encephalopathy is based on an effective intracerebral reduction of the ammonia concentration by 61%. The actual concentrations of the neurotransmitters were not significantly modified by the therapy. This opens to question the hypothesis that the neurotransmitters are responsible for the development of hepatic encephalopathy.

Plasma and cerebrospinal fluid amino acid patterns in hepatic encephalopathy

Plasma and cerebrospinal fluid amino acid levels wee measured in 12 cirrhotic patients in grade 0 hepatic encephalopathy and 17 in grade 3-4 hepatic encephalopathy. In 5 of these patients amino acid determinations were performed during the evolution of the encephalopathy. No correlation was found between the degree of hepatic encephalopathy and the plasma amino acid imbalance. In the CSF of cirrhotic patients without encephalopathy, a significant increase was found in nearly all amino acids, including those known to not easily cross the blood-brain barrier; this suggests the presence of a nonspecific modification of the blood-brain barrier permeability. In patients with severe hepatic encephalopathy, the further increase only in cerebrospinal fluid aromatic amino acids and methionine levels suggests the presence of a selective stimulation of the neutral amino acid transport system across the blood-brain barrier. Finally, the good correlation between glutamine and the sum of neutral amino acids found in the cerebrospinal fluid only in the presence of encephalopathy supports the hypothesis that brain glutamine may stimulate neutral amino acid transport across the blood-brain barrier.

Evidence for central hypertyraminemia in hepatic encephalopathy

In mongrel dogs, the effect of end-to-side portacaval shunt on plasma, cerebrospinal fluid (CSF) and brain tyramine, tyrosine, dopamine, norepinephrine, and epinephrine were studied. It was found that the level of tyramine in plasma, CSF, and selected brain regions increased steadily after the construction of the shunts. These elevations became more pronounced when the dogs manifested symptoms of hepatic encephalopathy. In postshunted dogs with stage II and III hepatic encephalopathy, tyramine concentration in corpus striatum (1,312 +/- 371), hypothalamus (400 +/- 67.0), and midbrain (660 +/- 78.7 ng/g) was significantly (P less than 0.05) higher than the level in dogs with stage 0 and I hepatic encephalopathy and sham-operated dogs serving as controls (corpus striatum, 831 +/- 140; hypothalamus, 167 +/- 40.0; and midbrain, 132 +/- 37.4 ng/g). This was followed by a concomitant depletion of dopamine and norepinephrine in these brain regions (postshunt: dopamine 104 +/- 20.0, 3,697 +/- 977, and 105 +/- 14.1; norepinephrine 521 +/- 71.6, 81.6 +/- 13.7, and 218 +/- 31.7 ng/g; vs. sham group: dopamine 532 +/- 83.1, 8,210 +/- 1,126, and 192 +/- 35.0; norepinephrine 1,338 +/- 425, 124 +/- 21.3, and 449 +/- 89.7 ng/g) of encephalopathic dogs with portacaval shunt. Furthermore, tyramine, tyrosine, dopamine, and norepinephrine levels in plasma and CSF increased markedly as clinical features in the dogs' behavior characteristic of hepatic encephalopathy occurred, including hypersalivation, ataxia, flapping tremor, somnolence, and coma. Cerebral hypertyraminemia and a defect in sympathetic neurotransmission may contribute to the development of hepatic encephalopathy of liver disease.

CNS tryptamine metabolism in hepatic coma

Lumbar CSF indoleacetic acid (IAA) was higher in patients with cirrhosis of the liver than in controls. It was also higher in CSF of patients in coma than in those with hepatic cirrhosis but not in coma. There was a strong correlation (r = 0.89, p less than 0.01) between the grade of hepatic coma and CSF IAA. These data indicate that there is an association between elevated CNS tryptamine metabolism and hepatic coma. How far changes in the metabolism of tryptamine and other trace amines are relevant to the induction of hepatic coma or are simply a reflection of advanced liver dysfunction is unclear.

A longitudinal study of tryptophan involvement in hepatic coma

Previous cross-sectional studies have demonstrated that hepatic coma is associated with abnormally high levels of plasma free tryptophan. Establishment of a more definitive relationship between this biochemical abnormality and hepatic coma requires an evaluation of biochemical changes in individual patients as they undergo alterations in the function of their central nervous systems. The present report is an evaluation of tryptophan and substances believed to influence its entry into the brain in six patients whose clinical status progressed from hepatic coma to complete recovery. Consistent significant decreases in plasma free tryptophan and free fatty acids were demonsrated to occur as the patients recovered. No consistent changes, however, were found in the plasma levels of the amino acids which have been reported to compete with tryptophan for transport across the blood-brain barrier, except for leucine which was significantly decreased in all six patients upon recovery from coma. Assay of lumbar cerebrospinal fluid for both tryptophan and the serotonin metabolite, 5-hydroxyindoleacetic acid (5-HIAA), showed no consistent changes as the patients recovered from hepatic coma.

Cerebrospinal fluid glutamine levels and EEG findings in patients with hepatic encephalopathy

The cerebrospinal fluid glutamine level was determined and an electro-encephalogram was made at roughly the same time in 41 patients on 55 occasions. A modified electro-encephalographic grading for practical use was introduced, because the classical electroencephalographic grading described by PARSONS-SMITH et al. (1957) does not apply to patients in deep coma. A significant correlation was found between the natural logarithms of cerebrospinal fluid glutamine levels and the electro-encephalic grade. In combination, these parameters provide valuable diagnostic and prognostic information in hepatic encephalopathy, and each can serve separately for follow-up purposes.

[Inhibitory effect of cerebrospinal fluid on the activity of sodium-, potassium-ATPase in animal brain synaptic membranes]

Liquor cerebrospinalis, obtained from patients with various diseases, inhibited Na, K-ATPase from rat and bovine synaptic membranes and did not influence on the activity of Mg-ATPase. The inhibition was independent on the type of disease. The inhibitory effect of liquor cerebrospinalis disappeared after dyalisis of it against Krebs-Ringer solution. Liquor cerebrospinalis appears to contain an endogenous inhibitor of synaptic Na,K-ATPase, which controls the enzymatic activity in vivo.

A selective radioenzymatic assay for the determination of octopamine and phenylethanolamine in plasma and cerebrospinal fluid. Preliminary results in human and experimental hepatic encephalopathy

A sensitive radioenzymatic assay for the simultaneous determination of phenylethanolamine and octopamine in biological fluids is described. It is derived from the radioenzymatic assay originally described by Molinoff et al. (1969) and subsequently modified by Saavedra (1974). The enzymatic reaction is based upon the methylation of phenylethanolamine and octopamine by phenylethanolamine-N-methyl transferase using 14C-S-adenosylmethionine as the methyl donor. The N-methyl derivatives of the two amines are separately extracted and estimated. Selectivity is increased by optimization of extraction and evaporation and by subsequent extraction of the two compounds. Phenylethanolamine and octopamine levels were determined in plasma of human subjects and in plasma and CSF of dogs. The levels were found significantly elevated both in human and experimental hepatic encephalopathy.

Alterations in plasma and CSF amino acids, amines and metabolites in hepatic coma

The dog with an end-to-side portacaval shunt (PCS) has been extensively used as a model to investigate hepatic encephalopathy (HE) as it demonstrates a plasma amino acid pattern similar to patients with chronic liver disease. In adult mongrel dogs, the effect of PCS on plasma and CSF amino acids, octopamine (OCT), phenylethanolamine (PEA) and CSF 5-hydroxyindolacetic acid (5-HIAA), were studied. Moreover, the effect of correction of plasma amino acids by infusional techniques was investigated.Tyrosine, tryptophan and phenylalanine levels increased dramatically during the development of HE in plasma and CSF, while valine, leucine and isoleucine decreased in plasma only, but CSF levels remained stable. Plasma and CSF octopamine and phenylethanolamine and CSF 5-HIAA increased markedly as clinical features in the dogs' behavior, characteristic of hepatic encephalopathy occurred, including hypersalivation, ataxia, flapping tremor, somnolence and finally coma. Once in coma, the dogs were infused with an amino acid mixture (F080) calculated to normalize the plasma amino acid pattern. After one to eight hours, the dogs began to awake. Simultaneously, blood, and CSF aromatic amino acids returned to their control values, as did OCT, PEA and CSF 5-HIAA. If F080 infusion was stopped, biochemical alterations would appear within one week, again accompanied by clinical hepatic encephalopathy.The results indicate that the altered levels of aromatic and branched chain amino acids, octopamine and PEA in plasma and CSF correlate well with the development of HE and that correction of the plasma amino acid abnormalities improves encephalopathy simultaneously with correction of neurotransmitter derangements in CSF.

Citrulline as a diagnostic parameter and a major amino acid constituent of cerebrospinal fluid in hepatic coma

Free amino acids of cerebrospinal fluid and serum in hepatic coma have been studied. Citrulline was found to form about 80% of the total free amino acids in cerebrospinal fluid, whereas serum contained slightly higher levels of tyrosine, methionine, phenylalanine and glutamine. The higher level of citrulline in cerebrospinal fluid may be attributed to the inhibition of argininosuccinic acid synthetase in this disease.

Studies on cyclic AMP in different compartments of cerebrospinal fluid

Adenosine 3', 5'-monophosphate (cAMP) was measured in the CSF of 42 patients undergoing radiological investigation, neurosurgical procedures, or investigation of hepatic coma. The concentration of cAMP was significantly higher in ventricular CSF than in lumbar CSF. Premedication with pentobarbitone plus promethazine increased cAMP in lumbar CSF. There was no difference in cAMP concentration in lumbar CSF obtained before or after injection of air or after the administration of diazepam during lumbar pneumoencephalography. Lumbar CSF cAMP concentration was significantly increased in patients in hepatic coma. The concentration of cAMP in the lateral ventricle was not affected by general anaesthesia or by the presence of a complete block of the aqueduct of Sylvius. There was no decrease in lumbar CSF cAMP in patients with a complete stenosis of the aqueduct of Sylvius, partial blocks of CSF flow at the cervical level, or a complete block at the lower thoracic level. The concentration of cisternal CSF cAMP was similar to that of lumbar CSF. These results suggest that (1) there is a ventriculolumbar gradient in the concentration of cAMP but of insufficient magnitude to be detected by mixing of lumbar and ventricular CSF during pneumoencephalography, (2) lumbar CSF cAMP concentration is not dependent on brain as a source of this nucleotide; the source of this nucleotide may be largely derived from the spinal cord, (3) premedication may affect the concentration of cAMP in lumbar CSF cAMP, (4) the formation of cAMP is unimpaired in hepatic coma.