Comparison of the kinetics and utilisation of D(-)-and L(+)-sodium lactate in normal man

After infusion of sodium D(-)L(+)-lactate in healthy man the clearance of the D(-)-isomer from blood was 70% of that of the L(+)-isomer. Utilisation of L(+)-lactate may have been inhibited by the presence of the D(-)-isomer. The changes in blood pyruvate concentration and ketone body ratio were compatible with mitochondrial oxidation of D(-)-lactate to pyruvate. After infusion of a D(-)L(+)-lactate racemic mixture, the renal excretion of the D(-)-isomer was much greater than that of the L(+)-isomer, although peak blood concentrations of the L(+) were higher than those of the D(-)-isomer. After infusion of sodium L(+)-lactate, the renal excretion of D(-)-lactate increased 7 times, although no D(-)-lactate could be detected in the blood or in the sodium L(+)-lactate infused.

Increased excretion of lactate, glutarate, 3-hydroxyisovalerate and 3-methylglutaconate during clinical episodes of propionic acidemia

Metabolic changes dependent upon clinical conditions were studied in an eight-month-old girl with propionyl CoA carboxylase deficiency. Only methylcitric acid and 2-methyl-3-oxovaleric acid were detected in the urine of the patient under clinically favorable conditions. During episodes of clinical decompensation, she excreted increased amounts of all the metabolites associated with this disorder. Four acetyl CoA precursors increased during clinical episodes: glutaric acid, a catabolic intermediate of lysine; 3-hydroxyisovaleric acid and 3-methylglutaconic acid, catabolic intermediates of leucine; and lactic acid. This suggests that under clinically favorable conditions the patient has an altered propionate metabolism which proceeds via normal acetyl CoA metabolism with sufficient capacity for acetyl CoA plus propionyl CoA metabolism. When the production of propionyl CoA exceeds the metabolic capacity, however, the catabolism of potent ketogenic amino acids is effectively suppressed in order to reduce acetyl CoA production.

The metabolic disposition of the selective beta 1-adrenoceptor agonist prenalterol in mice, rats, dogs, and humans

The metabolic routes of the selective beta 1-adrenoceptor agonist prenalterol have been studied in mice, rats, dogs, and humans after oral administration. The drug was well absorbed from the gastrointestinal tract and most of the administered radioactivity was excreted in urine from all species within 24 hr. Prenalterol was metabolized to a varying extent in the species studied. About 20% of the 10-mg dose was recovered unchanged in man, the corresponding figures being 1.8% in the mouse, 7% in the rat, and 54% in the dog at 0.263 mg/kg (1 mumol/kg). Three metabolites were characterized and quantified by thin-layer chromatography, high-performance liquid chromatography, nuclear magnetic resonance (1H and 13C), and gas chromatography-mass spectrometry. Pronounced species variations in the metabolic pattern were observed. The phenolic sulfate ester of prenalterol was the main urinary metabolite in man, important in the dog, minor in the rat but not detectable in the mouse. Prenalterol glucuronide was formed in significant amounts in the animals and, in addition, beta-4(hydroxyphenoxy)lactic acid was present in dog urine. In the rat and the mouse the degree of biotransformation of prenalterol was significantly decreased at high oral doses of 2630 mg/kg (10 mmol/kg). The synthesis of prenalterol sulfate ester with use of ion pair extraction techniques is described.

A model of L(+)-lactate metabolism in normal man

Mathematical models were used to study the elimination of L(+)-lactate during and after an intravenous load of unlabelled sodium L(+)-lactate in 20 normal postprandial subjects. Clearance of L(+)-lactate from blood was 17.9 +/- 1.1 ml (kg BW)-1 min-1 and the endogenous production rate of L(+)-lactate at rest was 1.38 +/- 0.16 mol (70 kg BW)-1 24 h-1. Clearance and production were unchanged after a 36-hour fast in 4 subjects. Renal excretion of L(+)-lactate accounted for less than 1.2% of the infused load. Clearance of L(+)-lactate was closely related to the pre-infusion concentrations of ketone bodies and alanine.

Dietary treatment and biochemical studies on a neonatal case of propionyl-CoA carboxylase deficiency

The case of a patient with neonatal propionic acidaemia is reported. Despite an initially favourable response to the administration of an artificial formula, the patient finally died when 9.5 months old. Protein tolerance never exceeded 1.3 g kg-1 day-1. During the remission periods, when ingesting the formula, 3-hydroxypropionic acid was excreted alone or together with tiglylglycine and/or methylcitrate. In a period of ketoacidosis, in addition to these three metabolites and those of ketoacidosis, elevations of 2-methyl-3-oxovaleric acid, propionylglycine and 2-methyl-3-hydroxybutyric acid were found. A severe deficiency of propionyl-CoA carboxylase in cultured fibroblasts was detected; biotin, when added to the fibroblasts culture media, did not stimulate this enzyme activity. The effectiveness of the administered formula is discussed.

Chronic lactic acidosis in a patient with cancer: therapy and metabolic consequences

Lactic acidosis is a life-threatening disorder in some cases. Treatment should be directed at the primary cause. Sodium bicarbonate should be added if the acidosis is very severe, or if the rate of hydrogen ion production is very rapid and not controlled. In contrast, with moderate degrees of steady state lactic acidosis and poor dietary intake, the risks of therapy with sodium bicarbonate or dichloroacetate may actually outweigh the benefits in a cachectic patient unless a dietary glucose and/or protein load is given.

Lactic acid in urine of children with lower and upper urinary tract infection and renal obstruction

Preliminary evidence suggests that the concentration of lactic acid in urine may be a good means of distinguishing lower urinary tract infection (cystitis) from upper urinary tract infection (pyelonephritis) and may be helpful in detecting urinary tract obstruction. To test this hypothesis the lactic acid concentrations in 291 urine samples from 250 children were tested. Sixty-four patients had no bacterial infection and served as the control group. A second group (153 patients) had cystitis, and the third group (24 patients) showed radiologic, clinical, and laboratory evidence of pyelonephritis. A fourth group of nine patients who had prolonged urinary tract retention was also analyzed. Patients in the control group, as well as those with cystitis, showed relatively; low concentrations of urinary lactic acid. All levels were less than 2 mg/dl; (mean, 0.8 mg/dl; range, 0.1-2 mg/dl). Patients who had clinical pyelonephritis had lactic acid concentrations of 3.3 mg/dl (mean, 11.4 mg/dl; range, 3.3 mg/dl-40.5 mg/dl). There was no overlap in lactic acid concentrations between the two groups. Furthermore, lactic acid concentrations in urine from patients who had pyelonephritis gradually declined after the initiation of therapy, attaining a level of less than 1 mg/dl by the end of the treatment. Recurrence of the pyelonephritis was consistently documented by a renewed increase of urinary lactic acid concentration. Lactic acid levels were also elevated in urine samples collected immediately after relief of obstruction in the nine patients who had urethral obstructions, showing a mean concentration of 15.8 mg/dl (range, 4.2-37.2 mg/dl).

Two forms of biotin-responsive multiple carboxylase deficiency

Biotin-responsive multiple carboxylase deficiencies are classified into early and late forms. The early form showed higher urinary excretion of 3-hydroxyisovalerate and 3-hydroxypropionate than the late form and was associated with normal plasma biotin concentrations. It is proposed that holocarboxylase synthetase and intestinal biotin absorption are defective in the early and late forms respectively.

Hypermethioninaemia and 3-hydroxyisobutyric aciduria in an apparently healthy baby

An apparently healthy baby with persistent hypermethioninaemia excretes increased amounts of 3-hydroxyisobutyrate, 3-hydroxypropionate, beta-aminoisobutyrate and beta-alanine. A defect in the oxidation of methylmalonic and malonic semialdehydes is proposed but the cause of the hypermethioninaemia is obscure.

D-Lactic acidosis in a boy with short bowel syndrome

Metabolic acidosis in a 3-year-old child with short bowel syndrome led to the discovery of massive D-lactic aciduria. After normalisation of the intestinal bacterial flora, D-lactate disappeared together with the acidosis. Dysbacteriosis with excessive production of D-lactate by intestinal bacteria (unidentified) and subsequent absorption explains this unusual cause of metabolic acidosis.

A simple test for urinary lactic acid

A new simple rapid test for the detection of increased urinary lactic is described. The method depends on the transformation of lactic acid to acetaldehyde by cesium IV. Acetaldehyde reacts with sodium nitroprusside prducing a blue color. Patients from an emergency ward and patients with experimentally induced hyperlactatemia have been screened with this test. The results confirm that there exists a correlation between blood and urinary lactate levels and that a clinically relevant hyperlactemia is associated with an increased urinary lactate concentration which can be reliably detected with this test.

The response of the kidney of the freshwater rainbow trout to true metabolic acidosis

Infusion of lactic acid into the bloodstream of trout produced a short-lived depression of blood pH and a long-lasting elevation of blood lactate. The lactate injected was distributed in a volume of 198 ml/kg. Renal excretion of lactate anion and total acid increased by approximately equal amounts during the period of high blood lactate levels, but total renal loss over 72 h accounted for only 2% of the lactate load and 6% of the proton load. Comparable differences in the time courses of blood lactate and pH changes occurred when lactacidosis was induced endogenously by normocapnic hypoxia. The immediate response of the kidney was similar to that with lactic acid infusion, but there was a long-lasting (12–72 + h) elevation of urinary acid efflux that was not associated with lactate excretion. Following hypoxia, renal excretion over 72 h accounted for 1% of the estimated lactate load and 12–25% of the proton load. A renal lactate threshold of 4–10 muequiv/ml prevents significant urinary lactate excretion. The response of the trout kidney to true metabolic acidosis is similar to that of the mammalian kidney.

Tyrosyluria in marasmus

1. Plasma tyrosine and urinary p-hydroxyphenyl lactic acid (PHPLA) and p-hydroxyphenyl acetic acid (PHPAA) were studied in thirty patients with marasmus and twenty normal controls in the same age group. 2. In the control group conventional tyrosyluria was not observed but 30% of the group excreted high levels of PHPAA. In the group with marasmus, plasma tyrosine and urinary PHPLA and PHPAA values were signigificantly higher than the control values. However only 13.3% of the patients were considered to have conventional tyrosyluria and 52.3% were found to excrete high levels of PHPAA. 3. Administration of ascorbic acid resulted in a reduction of PHPLA excretion while it had no effect on PHPAA excretion. 4. It was inferred that (a) tyrosyluria in marasmus is due to the reduced activity of the hepatic enzyme 4-hydroxyphenyl pyruvate: oxygen oxidoreductase (hydroxylating, decarboxylating) (PHPAA-oxidase; EC 1.13.11.27) due to the deficiency of ascorbic acid and (b) high excretion of PHPAA is related to age and nutrition of the child and is unaffected by the administration of ascorbic acid. 5. It was further inferred that urinary excretion of PHPLA is a reliable index of tyrosyluria.

Determination of 3-mercaptolactate, mercaptoacetate and N-acetylcysteine in urine by gas chromatography

A method is described for the determination of 3-mercaptolactate, mercaptoacetate (thioglycolate) and N-acetylcysteine in urine. As these compounds are mainly excreted as their mixed disulfides with cysteine, they are first reduced to the free thiols by an insoluble polymer containing thiol groups. After purification by chromatography on an organomercurial adsorbent, the compounds are converted to benzyl derivatives by extractive alkylation and determined by gas chromatography. The identity of the compounds analyzed was verified by mass spectrometry. It was demonstrated that mercaptolactate and mercaptoacetate are almost entirely excreted as their mixed disulfides with cysteine, whereas appreciable amounts of N-acetylcyteine are present as the symmetrical disulfide and the free thiol. The urinary excretion of the compounds from healthy human beings was also studied.

Simultaneous and consecutive administration of nutrients in parenteral nutrition

In seven patients, six with Crohn's disease and one with pancreatitis, two methods of parenteral nutrition were compared: the partial consecutive administration of the components of a parenteral nutrition regimen versus the administration of all nutrients simultaneously. With respect to the consecutive regimen, the simultaneous infusion regimen gave an improvement in the nitrogen balance of 13% and a decrease in urinary lactic acid of about 50%. Urinary excretion of alpha-amino nitrogen, glucose, and fructose was very small in both cases but was slightly lower during the simultaneous infusion regimen. The improvement in the nitrogen balance attained with the simultaneous infusion regimen can be explained by the fact that infused nutrients, especially carbohydrates, cause fewer metabolic disturbances. The simultaneous infusion regimen has three other advantages. The patients rarely complain of headache and nausea, the infusion regimen is markedly simplified and the risk of contamination when nutrients are added to the infusion bottles in the ward is considerably diminished.

Organic acids in urine from preterm infants

The organic acid excretion was studied in urine samples from 26 preterm infants on the 1st and 5th days of life and the results compared to those obtained in 5 samples from full-term neonates. Gas-chromatography-mass spectrometry with a computer system was the method used in this work. The acids tabulated were those more closely related to lactic acidosis and the Krebs cycle. Great variations were found in the excretion of these acids in preterm infants in contrast to the very homogeneous pattern obtained in full-term neonates.