Plasma Ornithine Research Articles

Plasma arginine and ornithine levels and selected enzyme activities in uremic rats fed various amounts of arginine

Rats weighing 100 g were made chronically uremic by partial left renal artery ligation and contralateral nephrectomy. Rats with urea clearances below 0.30 ml/min and sham-operated controls were pair-fed arginine-free diets, diets containing normal amounts of arginine or diets with high levels of arginine. After 4 to 8 weeks, rats were killed and plasma levels of arginine, ornithine and lysine were measured. In addition, activities of various urea cycle enzymes in liver and kidney and renal transamidinase were determined. Plasma amino acid levels and enzyme activities of the urea cycle remained constant in control rats fed diets differing in arginine content. However, renal transamidinase activity was elevated in control rats fed arginine-free diets. In plasma of uremic as compared with control rats, arginine levels varied with the arginine intake, and lysine levels were elevated when arginine supplements were fed. With all diets, plasma ornithine remained constant in uremic rats at slightly but not significantly increased levels. Hepatic carbamoyl phosphate synthetase activity and renal arginine synthetase activity were reduced in uremic as compared to control rats. Renal transamidinase activity, expressed per g of kidney, was elevated in uremic rats with all diets except arginine-free. When amino acid diets were fed, hepatic arginase activity was higher in uremic rats and this increase was enhanced by arginine-free diets. Other enzyme activities in uremic rats were not affected by the amount of arginine in the diet.

Deficient L-ornithine: 2-oxoacid aminotransferase activity in cultured fibroblasts from a patient with gyrate atrophy of the retina

Gyrate atrophy of the retina is an autosomal recessive condition characterized by a specific progressive retinal degeneration and increased urine and plasma ornithine. This study demonstrates a deficiency of L-ornithine: 2-oxoacid aminotransferase (EC 2.6.1.13) activity in cultured fibroblasts from a patient with this disease.

Biochemical and ultrastructural changes in livers of cadmium-treated rats

Groups of male Wistar rats were given 0, 0.25, 0.50, or 0.75 mg of Cd/kg body wt sc 3 days/week for 8 weeks. At the times sampled, the fraction of total cadmium administered in the liver and kidney (40–50% in the liver and 6% in the kidney) remained constant. Until Week 6, no differences were found in plasma aspartate aminotransferase (AAT), γ-glytamyl transpeptidase (GT), and ornithine carbamoyl transferase (OCT) activities. At Week 6, GT and AAT activities became elevated. Small but significant changes in red blood cell carbonic anhydrase activity occurred at 6 and 8 weeks. Electron microscopic examination of liver tissue indicated dilatation of the rough endoplasmic reticulum and prolification of prominent connective tissue fiber bundles at Week 6. These results show a correlation between ultrastructural liver changes and elevations in plasma enzyme activities, which are usually considered to be indicative of chronic liver damage.

Role of zinc in the abatement of hepatocellular damage and mortality incidence in endotoxemic rats

Intraperitoneal administration of zinc (ZnIP) as zinc chloride prior to or simultaneously with a lethal quantity of intraperitoneally administered Salmonella typhimurium endotoxin significantly protected rats against toxin-induced mortality and hepatocellular damage. Pretreatment with amounts of zinc chloride ranging from 0.4 to 2.0 mg/100 g of body weight resulted in 80 to 100% survival compared with 10% survival in untreated control rats at 24 h after endotoxin treatment. Zinc chloride treatment in excess of 2.0 mg/100 g of body weight appeared to be toxic and provided diminished protection. In contrast with the protection obtained with ZnIP, intravenously administered zinc did not provide protection. The effectiveness of ZnIP to enhance survival if it was given after endotoxin was greatly diminished as a function of time after endotoxin. The extent of hepatocellular damage was assessed at various times after endotoxin administration in ZnIP-treated and untreated rats by measurement of plasma ornithine carbamoyltransferase activity and histological examination of liver sections. Endotoxin absorption from the peritoneal cavity and hepatic uptake were studied by using 51Cr-labeled endotoxin. ZnIP pretreatment significantly reduced 51Cr-labeled endotoxin content of blood and liver when compared to untreated controls, and effectively prevented endotoxin-induced elevations in plasma ornithine carbamoyltransferase activity and hepatic tissue necrosis. These data indicate that protection afforded by ZnIP treatment results as a consequence of the ability of zinc to diminish absorption of the toxin from the peritoneal cavity and subsequent hepatic uptake.

144: Gyrate atrofy of the choroid and retina and ornithine-ketoacid aminotransferase deficiency

In a 10 years old girl with gyrate atrofy of the choroid and retina plasma ornithine concentration was consistently elevated ranging from 1000-1250 μmol/1. The ornithine concentration of the spina fluid was similary increased. The concentration of the other amino-acids was normal in all samples. The urine showed a typical overflow aminoaciduria, with an increase in ornithine only The prenatal and postnatal history was generally uneventful. Nc clinical abnormality could be found; liver was not enlarged. Intelligence was normal. The following laboratory tests gave normal results: haematological examination, serum proteins and their electrophoretic pattern: SGOT, SGPT, LAP, γGT, bilirubin, ureum, creatinin, blood ammonia. A deficiency of ornithine keto-acid aminotransferase was found in cultured fibroblasts by radiochemical method. Pharmologic doses of Vit. B6 for 7 days and restriction of protein intake to 0.8 g/kg for 2 months did not result in normal plasma ornithine concentration. Normal ornithine concentrations were found in plasma of the parents and the healthy sibs.

The influence of abomasal supplements of zein and some amino acids on wool growth rate and plasma amino acids

SummaryMerino sheep were given abomasal infusions of (i) zein (80 g/day), (ii) zein (80 g/day) supplemented with L-lysine (6 g/day), L-tryptophan (1 g/day) or lysine and tryptophan together, or (iii) L-leucine (20 g/day). Effects on wool growth (length growth rate, fibre diameter, fibre volume growth rate and mass of wool grown) and on plasma amino acids were measured.Zein increased length growth rate and decreased fibre diameter; on average the volume growth rate and mass of wool grown were not significantly altered. The addition of tryptophan to the infusion of zein did not significantly alter wool growth, whereas the addition of lysine significantly increased all aspects of wool growth. The responses to these treatments were rapid and were adequately assessed during 12-day infusion periods. The infusion of leucine did not cause any appreciable changes in wool growth.Leucine supplementation increased the concentration of leucine in blood plasma about six-fold. Zein decreased the concentration of lysine and ornithine in plasma and increased the concentration of several essential amino acids; leucine was increased about seven-fold. The addition of tryptophan to zein had no effects on plasma amino acids, whereas lysine decreased the concentration of several amino acids in plasma and markedly increased lysine.

Plasma amino-acids in hereditary retinal disease. Ornithine, lysine, and taurine.

Plasma free amino-acids were measured in 41 patients with hereditary chorio-retinal degenerations including 26 with retinitis pigmentosa and five with gyrate atrophy of the choroid, six relatives of patients with gyrate atrophy, and 13 normal subjects. Patients with gyrate atrophy had very increased levels of ornithine and slightly decreased mean lysine values. Most relatives had slightly increased ornithine. Taurine, known to be deficient in the plasma of casein-fed cats with photoreceptor degeneration, was normal in all patients. Amino-acid precursors and metabolites of ornithine and taurine were also normal in the plasma. Although the association of high ornithine and gyrate atrophy appears constant, high levels of ornithine alone do not necessarily lead to this degeneration; one patient with known hyperammonaemia, homocitrullinuria and a tenfold increase in plasma ornithine was found to have a normal fundus appearance and normal electroretinogram.

Ornithine carbamoyl transferase activity: Use of a bovine liver extract in quality control

To obtain a pure ornithine carbamoyltransferase for quality control in clinical chemistry, the authors compared human plasma and bovine liver ornithine carbamoyltransferase. The data show that the K M of both enzymes are similar (respectively 1.03 and 1.33 mmol when ornithine is used as substrate; 1.02 and 1.06 mmol with carbamyl phosphate). The following properties are shown to be equivalent: linearity of the enzymatic reaction, inhibition by higher substrate concentrations, and temperature denaturation. The similarities between the two enzymes indicate that bovine liver ornithine carbamoyltransferase can be used in clinical chemistry quality control.

Effect of exercise, hypoxia, and epinephrine on lysosomes and plasma enzymes

In order to study the possible relation of hepatic lysosomal stability and enzyme release from the liver during stress, rats were sacrificed after swimming exercise, hypoxia, and epinephrine injections. Each of the stresses caused a decrease in hepatic lysosomal stability, an increase in plasma ornithine carbamoyltransferase (OCT), a liver specific enzyme, and increases in plasma creatine phosphokinase (CPK) and aspartate aminotransferase (AAT). With exercise, the decrease in lysosomal stability and the increase in OCT were first seen at one hour. The OCT increase preceded the lysosomal changes after hypoxia and followed the lysosomal changes after epinephrine injection. Prednisolone reduced the lysosomal and CPK (but not the OCT and AAT) changes with exercise, but had no effect with hypoxia or epinephrine injections. Adrenalectomy delayed the lysosomal changes and eliminated the increase in OCT after hypoxia and epinephrine. The varying time sequence of hepatic lysosomal changes and enzyme release with these stresses suggests that these two phenomena are not causally related.

Defective metabolic clearance of plasma arginine and ornithine in lysinuric protein intolerance

Fasting plasma lysine, arginine, and ornithine concentration is clearly statistically decreased in patients with lysinuric protein intolerance (LPI). In seven LPI patients and five reference subjects, one suffering from classic cystinuria, arginine and ornithine were infused intravenously at a stepwise-increased rate. Plasma steady-state concentration of the infused diamino acid was larger in LPI patients than in the reference subjects, although the patients lost more into the urine. The increase in plasma ornithine and urea concentration on arginine infusion was similar in both groups. Calculated metabolic clearance rates (MCR) of arginine and ornithine were clearly smaller in LPI patients than in the reference subjects. Infusion of lysine brought about a clear decrease in the MCR of arginine; this was similar in both groups of subjects. These findings suggest a defect in the transport of diamino acids into liver cells, such as has been earlier demonstrated in the renal tubuli. Such a general cellular transport defect of diamino acids would explain both basic characteristics of LPI: renal loss of diamino acids and slow urea synthesis.

RAISED PLASMA-ORNITHINE AND GYRATE ATROPHY OF THE CHOROID AND RETINA

In nine patients with gyrate atrophy of the choroid and retina, plasma, urinary, cerebrospinal-fluid, and aqueous-humour ornithine concentrations were ten to twenty times higher than in controls. The nine patients came from seven families. It is suggested that the basic metabolic abnormality in patients with gyrate atrophy of the choroid and retina is decreased activity of the enzyme ornithine-ketoacid aminotransferase.

DOPA and amino acid levels in plasma and cerebrospinal fluid of patients with parkinson's disease before and during treatment with L-dOPA

Plasma and cerebrospinal fluid (CSF) levels of DOPA and various amino acids were studied in the same groups of patients with Parkinson's disease before and during treatment with l-DOPA after 2–3 weeks. Peak levels of plasma DOPA were obtained usually 2–3 h after L-DOPA administration and average peak concentrations were 0.7 ± 0.4 μg/ml after the first and 0.6 ± 0.6 μg/ml after the optimal dose which was between 2 and 6 times higher than the initial dose. No correlation was observed between plasma DOPA levels and the dose administered or the clinical response of the patient. Before treatment plasma and CSF levels of various amino acids were not different from those found in a control group with the exception of plasma ornithine which was lower in the patient group. Treatment with l-DOPA for 2–3 weeks produced no changes in the amino acid pattern in plasma and CSF except for a significant increase in plasma proline and decrease in methionine in the CSF.

Carbohydrate and Amino Acid Metabolism in Lambs Fed Purified Diets Containing Urea or Isolated Soy Protein

A purified basal diet was pair-fed to five sets of twin lambs for comparing the effects of soybean protein (SP) or urea (U) on liver, heart, kidney, plasma and urinary concentrations of amino acids, metabolic intermediates and other constituents. Feed was available from 8 to 10 am and 1 to 3 pm daily during the entire feeding period of 76 days. Blood samples were drawn at 10 am once each week except on day 34 when samples were taken immediately before the morning feeding and at frequent intervals thereafter. NH3-N in peripheral blood following the am feeding was higher and blood glucose was lower in the U-fed lambs with blood urea being the same in both groups. Plasma lactate and succinate declined and blood glucose increased following feeding in both treatment groups. Plasma citrate increased after feeding in the U-fed lambs. During 6 hours after the morning feeding total urinary excretion of citrate, α-ketoglutarate and malate increased by factors of 12.2, 3.5 and 1.9, respectively, for U-fed lambs while their cis-aconitate excretion decreased. Plasma glutamate was higher at 1 pm than at 9 am, 11 am or 3 pm for both treatment groups. Plasma alanine, threonine, valine, leucine, isoleucine, lysine, ornithine and arginine were significantly lower in U-fed lambs but serine and glutamate were higher. Liver threonine, valine, leucine, isoleucine, lysine, histidine and ornithine concentrations were lower in U-fed lambs. Concentrations of valine and leucine were lower in the kidney and heart, isoleucine was lower in the heart, and lysine was lower in the kidney of U-fed lambs. Plasma Ca2+, Mg2+ and phosphate were the same for both dietary treatments.

The effect of urea in the diet of the early-weaned calf on weight gain, nitrogen and sulphur balance, and plasma urea and free amino acid concentrations

Experiments were conducted with 40 male Friesian calves between 5 and 11 weeks of age. The control diet contained meat meal as the sole protein supplement to grain, and this was replaced by urea to supply 20.1, 39.2, or 55.6% of the dietary nitrogen. The growth rate of the calves, when corrected for digestible dry matter intake, was significantly lower when urea supplied 55.6 % of the dietary nitrogen than when it supplied 0, 20.1, or 39.2% of the dietary nitrogen. The retention of nitrogen and sulphur was lower in the calves given 55.6% of the dietary nitrogen as urea, but the ratio of nitrogen to sulphur retained was constant for all diets. There was a positive correlation between dietary urea nitrogen intake and urea nitrogen concentration in the blood plasma. The urea nitrogen and a-amino nitrogen concentration in the blood plasma was greater in calves at 2 weeks of age than at 11 weeks of age. The concentrations of free glycine, valine, leucine, ornithine, lysine, and histidine in the blood plasma were significantly lower in the calves given the higher levels of urea in the diet.

Free amino acids in plasma, red cells and anaplasmata of parasitized calves

1. 1. Free and hydrolyzed free amino acids in plasma and erythrocytes of non-infected splenectomized calves and splenectomized calves parasitized with Anaplasma marginale were identified. 2. 2. Free and hydrolyzed free amino acids were identified in the parasites. 3. 3. Of twenty-seven ninhydrin-positive compounds found, twenty-one were identified as amino acids and quantities estimated. 4. 4. Parasitized animals had higher leucine, aspartic and α-amino- n-butyric acid and less threonine, proline, glycine, isoleucine, ornithine and arginine in plasma. 5. 5. Differences were found in amounts of individual amino acids in both plasma and erythrocytes. However, total amino acid nitrogen was nearly constant in infected vs. normal erythrocytes while a significant drop was observed in the plasma of infected vs. normal calves.

The venous plasma free amino acid levels of mother and child during delivery. 3. In a lower socio-economic group of a refugee area in Karachi, West Pakistan, with special reference to the "small for dates" syndrome.

SummaryThe plasma aminograms of mother's and cord vein plasma during delivery were studied in selected cases from a lower socio‐economi‐cal group in West Pakistan with a high incidence of intrauterine growth retardation of the foetus.There was a highly significant increase in the levels of the non‐essential amino acids glycine and ornithine in the mother's plasma and of glycine and proline in cord plasma. The plasma glycine/valine quotient was significantly increased in maternal as well as in cord plasma.It is suggested that the plasma glycine/valine quotient may serve as an index of subclinical protein undernutrition (low intake of dietary nitrogen) of mother and foetus and thus become a tool in the investigation of the immediate and late effects of this condition during pregnancy in human populations. The maternal quotient is not changed by short gestation or hypertensive disorder during pregnancy.

Effect of α-Aminoisobutyric Acid on Arginine Metabolism in Chicks

The addition of 0.5% α-aminoisobutyric acid (AIB), a presumably nonmetabolizable amino acid, to a casein basal diet supplemented with graded levels of L-arginine·HCl caused an accumulation of free arginine and a depression of free ornithine in both plasma and muscle of chicks, and also altered the levels of some other amino acids. The differential effect on free amino acids was more pronounced in muscle than in plasma. Injection of AIB into the breast muscle of chicks fed the casein diet supplemented with 3% L-arginine·HCl gave an effect on arginine, ornithine and other amino acids similar to that given by oral feeding of AIB. Further observations of significance were that the weight gain and feed efficiency of chicks fed the casein basal diet were improvd by supplementation with AIB, and that kidney arginase activity was greatly depressed when AIB was fed. Arginine metabolism was also affected by AIB in chicks fed a basal diet based on wheat gluten supplemented with arginine, but the growth response to AIB supplementation found with the casein diet was not observed. Possible mechanisms of the influence of AIB on arginine metabolism are discussed in relation to the experimental findings.

Incorporation of DL-[2-14C]ornithine and DL-[5-14C]arginine in milk constituents by the isolated lactating sheep udder.

1. Lactating mammary glands of sheep were perfused for several hours in the presence of dl-[2-(14)C]ornithine or dl-[5-(14)C]arginine and received adequate quantities of acetate, glucose and amino acids. 2. In the [(14)C]ornithine experiment 1.4% of the casein and 1% of the expired carbon dioxide came from added ornithine; 96% of the total radioactivity in casein was recovered in proline; 13% of the proline of casein originated from plasma ornithine. 3. In this experiment the results of chemical degradation of proline of casein as well as relative specific activities in the isolated products are consistent with the view that ornithine is metabolized, by way of glutamic gamma-semialdehyde, to proline or glutamic acid. 4. In the [(14)C]arginine experiments 3% of the casein and 1% of the expired carbon dioxide came from arginine; 84% of the arginine and 9% of the proline of casein originated from plasma arginine. 5. In these experiments the relative specific activities of arginine, ornithine and proline in plasma are in agreement with the view that arginine is metabolized by way of ornithine to proline. The conversion of arginine into ornithine is probably catalysed by arginase, so that arginase in mammary tissue may be involved in the process of milk synthesis.