[Therapy of chronic non-A, non-B hepatitis]

Before establishing the diagnosis of chronic active hepatitis (CAH) non-A-non-B other diseases have to be excluded, like toxic hepatitis (alcohol, drugs), immunological forms (autoimmune hepatitis, primary biliary cirrhosis), and metabolically caused hepatitis (hemochromatosis, Wilson's disease), since for some of these patients specific therapeutic procedures are available. History of the disease and repeated evaluation of control biopsies performed about every 9 to 12 months help in deciding about therapy. Chronic persisting hepatitis non-A-non-B and the mild form of CAH non-A-non-B do not need treatment but only diagnostic follow-up. Patients with apparent clinical disease, increased transaminases and histologically typical findings in at least two biopsies may be looked at as suitable for drug treatment. Since this disease is probably caused by virus, immunosuppressive therapy in this small group of patients described above has to be temporarily limited and should not be used as long term treatment.

[Immunosuppressive therapy in patients with HBeAg-positive chronic active hepatitis B?]

The course of HBsAg-positive chronic active hepatitis was followed in 36 patients who were treated by immunosuppression and in 45 controls by means of serial determinations of HBeAg titers and by repeated biopsies of the liver. In the treated group remission occurred in 52% (HBeAg negative) resp. 48% (HBeAg positive); in the control group these percentages were almost identical, that is to say 61% resp. 41%. During therapy 5 out of 9 HBeAg positive patients and 7 out of 12 HBeAg negative patients developed cirrhosis of the liver as compared to 5 resp. 10, and 2 resp. 12 patients in the control group. Judging from these results it seems unlikely, that the course of HBsAg positive, chronic-active hepatitis in patients, whose serum shows a positive HBeAg titer by immunodiffusion, might be influenced in a positive way by immunosuppressive therapy.

Activities of urea-cycle enzymes in chronic liver disease

The activities of urea-cycle enzymes were measured in liver biopsies of patients suffering from chronic-persistent hepatitis (CPH), chronic-active hepatitis (CAH) and liver cirrhosis. Most of the activities of urea-cycle enzymes did not differ in the case of CPH as compared to controls. Chronic-active hepatitis and liver cirrhosis are associated with a significant (p less than 0.05) decrease of enzyme activity as compared to normal persons. Most of the urea-cycle enzymes are significantly decreased in patients with CAH in comparison with CPH. No significant differences can be demonstrated in the case of CAH as compared to patients with complete cirrhosis. In conclusion, progression of chronic liver disease is associated with increasing alterations of enzyme activities catalyzing a liver specific metabolic pathway. The decrease of the activities of the key enzymes of the urea cycle (Carbamylphosphate-Synthetase and Arginino-succinate-Synthetase) is nearly identical both in CAH and liver cirhosis, although CAH may be a reversible disease. Therefore, marked alterations in the metabolic pathway of ammonia detoxification seem to preceed the histological manifestation of irreversible liver damage.

[Toxicity of ammonium acetate in rats with acute and subacute galactosamine-induced hepatitis (author's transl)]

Ammonia toxicity and the protective effect of arginine thereon were investigated in rats after single and repeated doses of galactosamine. Urea cycle enzymes and ornithine-oxo-acid transaminase activities were measured in rat liver homogenates. Ammonium acetate proved to be less toxic in rats treated with single or repeated doses of galactosamine than in untreated animals. Urea cycle enzyme activities of galactosamine-treated rats were clearly lowered. The protective effect of arginine against lethal ammonia intoxication was found in animals that had been treated with galactosamine as well as in untreated rats. Since the toxicity of ammonium acetate is lower in rats with galactosamine hepatitis, in which the activities of the liver urea cycle enzymes are reduced, it seems likely that ammonia detoxication in galactosamine-poisoned rat liver partly bypasses the urea cycle.

Influence of steroids on urea-cycle enzymes in chronic human liver disease

Activities of Krebs-Henseleit enzymes were determined in liver biopsies of normal persons and in patients suffering from alcoholic hepatitis and chronic active hepatitis. Prednisone was administered for five days in falling dosis (1.5 mg-0.5 mg/kg/body weight) to patients with alcoholic hepatitis and to controls. Patients with chronic active hepatitis received 15-20 mg prednisone daily for more than three months. In healthy persons prednisone did not influence the activities of Krebs-Henseleit enzymes. In patients with alcoholic hepatitis most of the urea-cycle enzymes are significantly decreased (p is less than 0.05) when compared to controls. After glucocorticoid administration enzyme activities remained unchanged. Activities of most of the urea-cycle enzymes are significantly (p is less than 0.05) decreased in untreated patients with chronic active hepatitis. In some of these patients, glucocorticoid administration was associated with a remission as proved by clinical, biochemical and histological data. Activities of the rate-limiting enzymes of the urea-cycle (ASAS, CPS) increased significantly in these patients. By contrast, alterations of enzyme activities could not be observed in patients who failed to respond favourably to steroid treatment.

Possible sites of interaction of acute renal failure with amino acid utilization for gluconeogenesis in isolated perfused rat liver

Experiments were performed to elucidate the mechanisms involved in the enhanced conversion of amino acids to glucose in acute uraemic rats. Increased gluconeogenesis from a mixture of serine, threonine, lysine, glutamate, ornithine and citrulline was confirmed using a non-recirculating perfusion system. Stimulation was concentration dependent, being most pronounced at physiological amino acid concentrations. Stimulation of glucose and urea formation could be mimicked by using serine alone whereas with lactate and pyruvate inhibition of gluconeogenesis was observed. Serine dehydratase activity was significantly elevated following nephrectomy. Further, the uptake of the non-metabolize amino acid alpha-aminoisobutyrate was considerably increased. It is concluded that serine may play a special role as substrate for the additional glucose formation in acute uraemic rats, probably mediated by an activation of serine dehydratase. Acceleration of amino acid transport seems to represent an additional component of stimulation of amino acid utilization in acute uraemia.

[Intracellular localisation of urea-cycle enzymes in liver (author's transl)]

Enzymes of the Krebs-Henseleit urea-cycle were localized by means of differential centrifugation and fractional tissue extraction in rat liver and in human liver. Argininosuccinatlyase (ASAL) and Argininosuccinatsynthetase (ASAS) represent enzymes of the soluble cytoplasmic fraction. Ornithine-ketoacid-transaminase(OKT), carbamyl-phosphate-synthetase (CPS) and ornithine-carbamyl-transferase (OCT) are localized in the mitochondrial and nuclei fractions of the liver cell. Most of the arginase activity is bound to subcellular structures (probably to nuclei). A small portion of arginase-activity was found in the soluble cytoplasmatic fraction. The enzymes of the Krebs-Henseleit urea-cycle are equally distributed in rat liver and in human liver. Differences in the subcellular localisation of (mitochondrial) enzymes in human liver could be attributed to mitochondrial breakage during tissue preparation and do not represent in-vivo conditions.

[Differentiation of cytoplasmatic, mitochondrial and lysosomal enzymes by fractional extraction of rat liver]

Enzymes of extramitochondrial, mitochondrial and lysosomal origin were differentiated by the method of fractional tissue extraction from rat liver. It could be confirmed that soluble enzymes of the extramitochondrial (cytoplasmatic) compartment (glycerine aldehydphosphate-dehydrogenase, argininosuccinate lyase) and soluble enzymes of the mitochondrial matrix can be differentiated easily according to their different intracellular localisation. Additionally, our results emphasize that soluble enzymes of both compartements and marker-enzymes of the lysosomal cell space which are known to be structurally-bound, can be differentiated too. However, the method failed to establish significant differences between enzymes located in the submitochondrial compartment (adenylatekinase, monaminooxidase and succinic-dehydrogenase) and lysosomal enzymes (cathepsin-D and N-acetyl-D-glucosaminidase).

Crystallization and some properties of glutamate dehydrogenase from rat liver

1. Glutamate dehydrogenase (L-glutamate:NAD(P) oxidoreductase, EC 1.4.1.3) from rat liver has been crystallized with a method carefully avoiding all denaturating agents. A 236-fold purification was achieved at a yield of 20%. The specific activity was 185 units/mg protein. The enzyme was homogeneous by analytical zone electrophoresis and sedimentation studies. The s0(20),w value was 13.2. 2. Sedimentation studies in the analytical ultracentrifuge and the behaviour of the enzyme in the disc-electrophoresis revealed that glutamate dehydrogenase from rat liver did not undergo a reversible association-dissociation reaction as reported of glutamate dehydrogenase of nearly all other mammalians. 3. Using antibodies prepared against crystalline bovine liver glutamate dehydrogenase, no immunological differences between the rat and the bovine liver enzyme could be observed.

A new method for the preparation of rat liver lysosomes. Separation of cell organelles of rat liver by carrier-free continuous electrophoresis

A combination of differential centrifugation and carrier-free continuous electrophoresis is introduced as a new method for the isolation of animal cell organelles. Various buffers were systematically checked in order to find the system which preserves the organelles and gives as well a good separation in the free-flow electrophoresis apparatus. Triethanolamine-acetate buffer (10 mM), pH 7.4 was used. The isolated lysosomes were pure according to marker enzymes and electron micrographs. A heterogeneity of the lysosomes in electrophoretic mobility was demonstrated with respect to the marker enzymes arylsulfatase and beta-glucuronidase. The lysosomes with higher mobility showed a maximum enrichment of 240-fold with respect to arylsulfatase. The lysosomes with lower electrophoretic mobility showed a 65-fold enrichment with respect to beta-glucuronidase. The ratio of beta-glucuronidase to arylsulfatase varied from 2:1 to 1:2 in lysosomes of different mobility. The yield amounted to approximately 1 mg of lysosomal protein per gram of liver protein. 5-8 mg of lysosomes can be obtained in one experiment. The electrophoretic separation proves to be an effective tool in obtaining pure and well preserved lysosomes.