Influence of essential amino acids and keto acids on protein metabolism and anemia of patients on intermittent hemodialysis.

Ten patients were treated with 10 g/day of essential amino acids orally; nine patients received 9.5 g/day of a mixture of essential amino acids (lysine, threonine, tryprophan, histidine, and tyrosine) and keto analogues of isoleucine, leucine, phenylalanine, valine, and methionine. A control group of 11 patients received no supplementation. All patients were on a liberal food intake amounting to 1 g of protein per kilogram of body weight and 31 kcal/kg of body weight daily. Before and 3 months after the beginning of the supplementation, the following parameters were measured: amino acids, albumin, transferrin, urea and creatinine concentrations in plasma, hemoglobin, and hematocrit in blood. None of these parameters was altered by either treatment. It is concluded that supplementation with essential amino acids or their keto analogues is ineffective in well-nourished dialysis patients.

Enzyme induction in the uremic liver.

Forty-five days after subtotal nephrectomy or sham-operation of male rats, microsomal enzymes were investigated in vitro. The activities (per milligram) of microsomal protein of two esterases and of two glucuronyltransferases were normal in the uremic rats. The mixed-function oxidation system had lower activities per milligram of protein than that in sham-operated controls. Due to a decrease of the microsomal protein content of the uremic liver, the activities of these enzymes were decreased when calculated for the whole liver. In contrast, the glucoronidation of phenolphthalein remained normal when related to the whole liver, due to an increased activity per mg of protein. Treatment with the plasticizer di-(2-ethylhexyl)-phthalate caused a significant increase of the liver wet weight, the microsomal protein content, and the activity per mg of protein for the demethylation of aminopyrine in subtotally nephrectomized rats but was without influence on the liver of sham-operated controls. It is concluded that uremia itself does not induce liver microsomal enzymes. The microsomal enzymes, however, remain inducible by foreign compounds even under uremic conditions.

Simultaneous hemofiltration/hemodialysis: an effective alternative to hemofiltration and conventional hemodialysis in the treatment of uremic patients.

Hemofiltration and hemodialysis were performed simultaneously with the Polyacrylnitrile membrane in a single pass dialyzate flow system. Due to the combination of convective mass transfer and diffusion, the clearances of both small and large molecules were significantly higher than during hemofiltration or hemodialysis alone. The removal of excess water was better tolerated than during hemodialysis. Six patients have been treated by this technique for 6 months 3 X 3 hr/week without side effects, and the new procedure appears to be the method of choice to shorten dialysis time.

Influence of silymarin on drug metabolizing enzymes in rat and man.

Male rats weighing 100-130 g were treated orally with a daily dose of 1 X 10 mg Legalon (active principle: silymarin)/100 g b.w. daily for 4 or 10 days. 4 and 10 days after the beginning of the pretreatment a significant increase of the activity of the mixed function oxidation system (Cytochrome P-450, aminopyrine demethylation, p-nitroanisole demethylation) was observed. No alteration of the body weight, the liver wet weight, the microsomal protein content, the cytochrome b5 content and the activities of glucose-6-phosphatase (G-6-Pase) and of a glucoronidase (4-methylumbelliferone) took place after the Legalon treatment. 4 h after the oral administration of 0.5 ml CCl4/kg b.w. the activity of the mixed function oxidation system and of the G-6-Pase was markedly decreased. This effect could not be prevented by the oral administration of 1 X 10 mg Legalon/100 g b.w. 6 h prior to CCl4 application. In human subjects the treatment with daily doses of 3 X 70 mg Legalon during 28 days had no influence on the metabolism of aminopyrine and phenylbutazone. From our results it is concluded that Legalon despite its effects in experimental animals has no influence on drug metabolism in man, when applied in therapeutic amounts.

Simultaneous hemofiltration/hemodialysis (HF/HD): short- and long-term tolerance. Introduction of a system for automatic fluid replacement.

Data are presented concerning our experiences with simultaneous hemofiltration and hemodialysis (HF/HD) in uremic patients. Ten randomly selected patients have been treated for two and a half to three years with either conventional hemodialysis (HD, 3 x 4 hours/week, 1.4 m2 surface area Cuprophan dialyzer) or HF/HD (RP-6, 3 x 3 hours/week). No differences could be detected with regard to the blood chemistry or the blood pressure between the two groups of patients. During HF/HD the well-being of the patients was better than during HD, which can be attributed to a greater stability of the blood pressure and of the serum osmolarity and to a decrease of the intraocular pressure during treatment. An apparatus is described which is in use enabling the automatic replacement of the required substitution fluid. With regard to the performance and the tolerance, HF/HD is comparable to hemofiltration, but the treatment sessions are shorter.

Potential role of middle molecular compounds in the development of uremic anemia.

In preceding papers it was demonstrated that middle molecular fractions isolated from uremic patients (MM) impair hemoglobin synthesis by inhibiting the enzyme Delta-aminolevulinic acid dehydrase (D-ALA-D) and by diminishing the globin synthesis in reticulocytes from healthy subjects. Additionally, the susceptibility to oxidative damage of erythrocytes is increased in the presence of MM. Studies were undertaken to elucidate the underlying mechanisms. It was found that the MM induced D-ALA-D inhibition is reversed both by Zn and by GSH in vitro indicating that MM exert their effect on the enzyme either by affecting essential SH-groups within the enzyme molecule or by altering the enzyme configuration by interaction with the Zn atom. MM causing an increased oxidative hemolysis rate (OHR) also inhibit the catalase activity and the glucose consumption of normal and uremic erythrocytes. It is concluded that the augmented OHR in uremia is induced by accumulating hydrogen peroxide which cannot be sufficiently removed due to the MM mediated catalase inhibition and the concomitant impairment of the glucose utilisation.

Influence of the plasticiser di-2-ethylhexyl-phthalate on drug metabolising enzymes in the liver of uraemic rats.

After bilateral or subtotal nephrectomy male rats were given intraperitoneal injections of the plasticiser di-2-ethylhexylphthalate (DEHP) at differing time intervals in doses that do not affect the liver of normal rats. 200mg DEHP/100g body weight had no influence on the parameters measured. After administering 7 x 200mg/100g body weight for 14 days, liver weight and in vitro activity of the mixed function oxidation system increased significantly. In addition, the hexobarbital sleeping time decreased, indicating a stimulation of the activity of drug metabolising enzymes in vivo. Similar results were obtained after the administration of 56 x 50mg DEHP/100g body weight for 19 weeks. It is concluded that uraemic rats are more susceptible to inducing effects, but that the DEHP toxicity is of little importance.

Porphobilinogen and porphyrin synthesis in reticulocytes from uraemic patients.

Since no information exists concerning porphyrin metabolism in uraemic patients we have measured the activities of delta-aminolaevulinic acid dehydrase (D-ALA-D) and porphobilinogen desaminase (PBG-D) in reticulocytes from uraemic patients, anaemic patients without uraemia and in healthy subjects. Despite a severe anaemia uraemic patients had the same amount of reticulocytes/mul blood. In uraemic patients D-ALA-D activity was reduced to about 20% compared to healthy subjects, PBG-D in uraemia was decreased to about 70%. It is concluded that porphyrin metabolism is altered in uraemic patients.

Influence of essential amino acids and keto acids on protein metabolism and the anaemia of patients on chronic intermittent haemodialysis.

Ten patients were treated with 10 g essential amino acids per day orally; 9 patients received 9.5 g of a mixture of essential amino acids (Lys, Thr, Try, His, Tyr) and ketoanalogues of Ile, Leu, Phe, Val, Met per day and a control group of 11 patients received no supplementation. All patients were on a liberal food intake amounting to 1g protein/kg body weight and 31 kcal/kg body weight daily. Before and three months after the beginning of supplementation the following parameters were measured: serum concentrations of albumin, transferrin, urea, creatinine, blood haemoglobin content and haematocrit, activities of the enzymes delta-aminolevulinic acid dehydrase and porpho-bilinogen desaminase, and globin synthesis in peripheral red blood cells. After treatment with either essential amino acids or keto acids a significant stimulation of globin synthesis occurred. None of the other parameters was altered. It is concluded that in well-nourished patients supplements of essential amino acids or keto acids are ineffective.

Influence of middle molecules on the anemia of uremic patients.

To evaluate their toxicity at the cellular level, middle molecules from uremic serum were incubated with erythrocytes from healthy subjects and the activity of the enzyme Delta-aminolevulinic acid dehydrase (D-ALA-D) and peroxidative hemolysis were investigated. Uremic middle molecules caused a significant decrease of the D-ALA-D activity of normal erythrocytes which was not due to differences in the concentrations of Pb, Cd or Zn. The decreased enzyme activity could be restored by adding reduced glutathione (GSH; 5 mmol/L) together with the middle molecules to the assay system. Uremic middle molecules caused a significant increase of peroxidative hemolysis in normal erythrocytes. Uremic middle molecules contribute to the anemia of uremic patients by impeding hemoglobin synthesis and by increasing peroxidative hemolysis, possibly by affecting SH-groups. H2O2-producing compounds should be avoided in uremic patients.

Hemodiafiltration: a new alternative to hemofiltration and conventional hemodialysis.

A new dialysis method, termed hemodiafiltration, is proposed. The procedure consists of the combination of hemofiltration and conventional hemodialysis using high flux membranes with a transmembrane pressure (TMP) of 300--500 mmHg and a dialysate flow of 900 ml/min. Due to the combination of convective mass transfer and diffusion, the clearance values of both small and larger molecules are significantly higher than during hemofiltration or hemodialysis alone with the same membranes. The removal of excess water is better tolerated than during hemodialysis. With this new method, six patients have been successfully treated for six months (three times per week, three hours per treatment) without side effects. Thus hemodiafiltration appears to be the method of choice to shorten dialysis time.

Globin synthesis in uraemia.

Globin synthesis was measured by incubating washed packed red cells with a balanced amino acid mixture and 14C-Histidine. After globin had been isolated from the haemolysate the 14C-incorporation rate per 10 mg globin per min was estimated. With regard to globin synthesis no differences existed between patients on chronic intermittent haemodialysis therapy (n equals 41), patitents suffering from secondary anaemia due to chronic infection, rheumatism or malignant diseases (n equals 21) and healthy subjects (n equals 37). Patients with acute bleeding on the other hand, had significant higher 14C-incorporation rates caused by an increase of the reticulocyte count mu1 blood (n equals 13). When substances retained in renal failure were added to the incubation mixture a marked inhibition took place with guanidinosuccinic acid, methylguanidine and fraction containing peptides with a molecular weight between 1200-1400 present in uraemic serum and normal urine, but not in serum from patients without renal failure.

Continuous peritoneal dialysis (CPD)--an alternative to hemodialysis in acute renal failure after cardiovascular operations.

In our experience hemodialysis proved to be unsatisfactory in the treatment of acute renal failure after cardiovascular surgical intervention because of its negative influence on the often critical hemodynamic situation of the patients. In 21 cases we performed a continuous peritoneal dialysis (CPD) for 1 to 29 (mean 9.2) days by using a Tenckhoff catheter (16). Treatment was started when anuria occurred or when serum nonprotein nitrogen increased. Satisfactory volume equilibration was established by this treatment. A pathological increase of serum electrolytes could be prevented; serum potassium, in particular, did not exceed 5.6 mVal/l. No dysfunctions in acid-base balance occurred. The serum levels of nonprotein nitrogen decreased: Serum carbamid was diminished from 229 +/- 14 mg% to 160 +/- 10 mg% and serum creatinine from 7.7 +/- 0.6 mg% to 6.0 +/- 0.8 mg% (p < 0.05). Disturbances of hemodynamic and respiratory functions could be avoided by CPD. Peritoneal reactions were noted in 5 cases. In our opinion continuous peritoneal dialysis seems to be a suitable alternative to hemodialysis in the treatment of acute renal failure after open heart surgery.