Urinary excretion of acetaminophen and its metabolites as studied by proton NMR spectroscopy

Acetaminophen and its glucuronide, sulfate, N-acetyl-L-cysteinyl, and L-cysteinyl metabolites can be rapidly detected by 1H NMR spectroscopy of intact, untreated human urine. Study of the time course of excretion of these metabolites in five clinically normal men after ingestion of the usual 1-g therapeutic dose of the drug showed that the mean 24-h excretion of the drug and these metabolites as determined by NMR was 77.3% of the dose. Respective relative proportions of the above metabolites were 49.9%, 37.6%, 3.0%, and 9.5% (L-cysteinyl plus free drug). Excretion of some other metabolites in urine, including creatinine, citrate, hippurate, and sarcosine was measured concurrently. Excretion of creatinine and sarcosine was closely correlated.

Benzyl alcohol toxicity in a neonatal intensive care unit. Incidence, symptomatology, and mortality

We unknowingly "screened" all NICU infants for elevated levels of serum benzyl alcohol (Bz-OH) over a three-month period. The fortuitous "screening" procedure resulted from the interference by Bz-OH with a routine blood CO2 assay used for all infants; validity was proved by (1) replication of the interference pattern with Bz-OH or benzoic acid; (2) confirmation of elevated benzoic acid levels in serum in two of the four screening positive infants tested but not in control infants, and (3) disappearance of the interference patterns when Bz-OH solutions were discontinued in affected infants. Screened Bz-OH-positive infants were compared to screened negative control infants, matched for weight (less than 1000 g), severity of RDS (on respirators), exposure to Bz-OH, and survival for longer than 48 hours. Intraventricular hemorrhage (IVH), metabolic acidosis appearing prior to IVH, and mortality were increased in Bz-OH-positive infants (P less than .05 in each case); hyperbilirubinemia and thrombocytopenia were not. Gasping respirations were not a major symptom. It is concluded that Bz-OH poisoning was a major cause of morbidity and mortality in NICU infants weighing less than 1000 g at birth during the three-month screening period. A retrospective review of patient records covering a 16-month period showed significant improvement in the survival rate of infants weighing less than 1000 g following the discontinuation of Bz-OH solutions.

The metabolism of cinnamic acid by healthy and phenylketonuric adults: a kinetic study

The enzyme phenylalanine ammonia lyase taken orally has been found to reduce the rise in blood phenylalanine that normally occurs following a protein meal. Therefore the enzyme has a potential use in the management of the genetic disease phenylketonuria. The enzyme mediates the conversion of phenylalanine to cinnamic acid and its possible clinical future has necessitated a more detailed study of the product of its reaction. Cinnamic acid is a compound of low toxicity which is converted in the mammalian body primarily to hippuric acid. We have examined the kinetics of this process in a healthy male and in two patients with untreated phenylketonuria. In addition we have attempted to clarify the inconsistencies in earlier published work about the status of other, minor metabolites. Following an oral load of sodium (2H6) cinnamate there is an increase in urinary hippuric acid largely due to the excretion of (2H5) hippuric acid. In the subjects studied there was no major difference in the rate of elimination although the amount of cinnamic acid converted was less in those with phenylketonuria. This may reflect reduced first-pass absorption by the liver in untreated phenylketonuria enabling increased uptake to occur in other parts of the body.

Formaldehyde generation from methenamine salts in spinal cord injury

To achieve effective suppression of bacteriuria in spinal cord injured (SCI) patients, methenamine mandelate and methenamine hippurate are commonly given with ascorbic acid. Since the effectiveness of ascorbic acid as a urinary acidifier has been challenged and as it also has been suggested that methenamine salts do not produce effective urine formaldehyde concentrations in patients with indwelling urethral catheters, we studied two groups of SCI patients to determine (1) the effect of ascorbic acid on urine pH and formaldehyde concentration when administered with methenamine salts; (2) the effect of an indwelling urethral catheter versus intermittent catheterization on formaldehyde concentration in the urine of SCI patients taking methenamine salts; and (3) the relative urine formaldehyde concentrations produced by treatment with methenamine mandelate and methenamine hippurate in SCI patients. Methenamine mandelate produced significantly higher urine formaldehyde concentrations than did methenamine hippurate, especially among patients with intermittent catheterization. Ascorbic acid produced a significant effect on urine pH but not on formaldehyde concentration.

Styrene metabolism in man: gas chromatographic separation of mandelic acid enantiomers in the urine of exposed persons

D- and L-mandelic acid are separated by gas chromatography as isopropyl ester or isopropyl ester-isopropyl urethane on capillary columns, coated with Chirasil -Val. For its determination in urine the isopropyl ester procedure gives better results because other components of the urine do not cause interference. Thus D- and L-mandelic acid in the urine of exposed workers could be detected and verified by means of GC/MS. Occupational styrene exposure near the MAK-value (100 ppm) results in a L/D-enantiomer-ratio in urine of nearly 1.5.

Potentiation by piridoxilate of the synthesis of hippurate from benzoate in isolated rat hepatocytes. An approach to the determination of new pathways of nitrogen excretion in inborn errors of urea synthesis

The synthesis of hippurate from benzoate as compared to ureagenesis has been investigated in isolated rat hepatocytes. Half-maximal synthesis of hippurate was observed at 0.3 mmol/l benzoate. In the presence of 1 mmol/l benzoate, hippurate synthesis proceeded linearly with time at a rate of 40 +/- 10 mumol X h-1 X g-1 dry weight. This provided less than 10% of nitrogen epuration supported by concomitant urea synthesis (350 +/- 82 mumol X h-1 X g-1 dry weight). The incorporation of benzoate to hippurate was markedly limited by the availability of glycine. Half-maximal hippurate synthesis was observed at 2 mmol/l glycine. In the absence of glycine, piridoxilate, a glyoxylate derivative, markedly potentiated hippurate synthesis. Half-maximal stimulation was observed at 10 mmol/l piridoxilate. In the presence of 10 mmol/l piridoxilate, hippurate synthesis (420 +/- 35 mumol X h-1 X g-1 dry weight) provided more than 50% of nitrogen epuration supported by urea synthesis. It is concluded that supplementation with nitrogen-free analogues of glycine such as piridoxilate are required to potentiate hippurate synthesis in an attempt to replace ureagenesis as an alternative pathway of waste nitrogen excretion in inborn errors of urea synthesis.

Clinical evaluation of Tc-99m N,N'-bis(mercaptoacetyl)-2,3-diaminopropanoate as a replacement for I-131 hippurate: concise communication

A clinical comparison of Tc-99m N,N'-bis( mercaptoacetyl )-2,3- diaminopropanoate (Component A) (Tc-99m CO2-DADS-A) and I-131 hippurate was conducted in a series of five normal volunteers and 18 patients. Each subject was studied in one session with Tc-99m CO2-DADS-A and I-131-hippurate; digital and analog images were recorded for 30 min and after voiding. In the normal volunteers, digital images with Tc-99m CO2-DADS-A gave a kidney-to-background ratio at 3 min that was greater relative to I-131 hippurate, a leading-edge parenchymal transit time that was similar to I-131 hippurate, and a percent injected dose in the urine at 30 min that was slightly less than I-131 hippurate (p less than 0.05). In patients (serum creatinine 1.0 to 14.3 mg/dl), decreasing renal function impaired excretion of Tc-99m CO2-DADS-A more than that of I-131 hippurate (p less than 0.01). In analog images, Tc-99m CO2-DADS-A always gave superior spatial resolution. No evidence of hepatobiliary excretion was detected with either radiopharmaceutical. We conclude that Tc-99m CO2-DADS-A and similar compounds should be pursued as possible replacements for I-131 hippurate.

[Radionuclide determination of renal clearance equivalent to physiological clearance measurements]

The concept of renal clearance in nuclear medicine describes the tubular secretion and glomerular filtration of a substance being removed from the blood plasma. The concept of clearance as used physiologically is rather wider and includes consideration of the outflow of the substances remained back in the kidneys. The present paper discusses clearance measurements as seen from a thermo-dynamic point of view, in which isotope clearances become equivalent with the physiological concept of clearance. In addition, it is possible to quantify each single step of the excretory function of each kidney separately.

Decline of blood and alveolar toluene concentration following two accidental human poisonings

In two workers admitted to hospital because of a coma due to an accidental occupational exposure to a mixture of solvents, the level of toluene was respectively 823-1122 micrograms/l in the blood and 53-38 micrograms/l in the alveolar air on the second day of admission (36 h after the accidental exposure). On the fifth day, 112 h after exposure, the toluene level was 120-45 micrograms/l in the blood and 3-1 micrograms/l in the alveolar air. The urinary excretion of o-cresol, calculated as a toluene equivalent, was 0.8-0.9 mg on the second day and 1.7-1.6 mg on the third day. Urinary hippuric acid, as a toluene equivalent, was 1.7-1.4 g on the second day and 1.3-0.7 g on the third day. A half-life of between 19 and 21 h was calculated for toluene both in the blood and in the alveolar air.

Urinary excretion of hippuric acid and o-cresol after laboratory exposure of humans to toluene

The urinary excretion of hippuric acid and o-cresol was studied after respiratory exposure of human volunteers to approximately 80 ppm (306 mg/m3 +/- SD 13) of toluene for 2 h under different work loads (0, 50, 100, 150 W, respectively, during 30-min periods). The diet before and after exposure varied. An isotachophoresis method for the determination of hippuric acid is described. The correlation between the total urinary excretion, excretion rate and concentration of hippuric acid, and the respiratory uptake of toluene was poor or non-existing. The same was true for the excretion of o-cresol, which 4 h after exposure was concluded amounted to 0.03-0.26% of the toluene uptake. Thus, after a short-time exposure neither metabolite proved to be a reliable measure of individual toluene uptake at varying workloads or food intake in combination with low exposure levels.

Determination of nine catecholamine metabolites and 5-hydroxyindolacetic acid in urine by capillary gas chromatography

A method is described for the simultaneous determination of nine urinary acidic and alcoholic catecholamine metabolites and urinary 5-hydroxyindolacetic acid. Incubation of a urine sample in the presence of ascorbic acid, glucuronidase and acylase and subsequent extraction with ethyl acetate precedes derivatization to trimethylsilyl compounds, capillary gas chromatographic separation and flame-ionization detection. The automated dual injection procedure and the analytical characteristics of the proposed method are reported in detail. Special attention is paid to problems that occur in analysis on a routine basis.

Urinary hippuric acid and orthocresol excretion in man during experimental exposure to toluene

It is not known whether urinary excretion of hippuric acid (HA) or orthocresol (O-Cr) is to be preferred for the biological monitoring of workers with occupational exposure to toluene. To study this, 42 printing trade workers with more than 10 years' exposure to a mixture of organic solvents including toluene (0-20 ppm) and 43 control subjects matched by age, smoking habits, and living accommodation were investigated. Each matched pair was randomised to an experimental exposure of either 100 ppm or 0 ppm toluene for 6.5 hours under controlled conditions in an exposure chamber. Urinary excretion of HA and O-Cr was determined by high pressure liquid chromatography from samples obtained before exposure, during the first three hours, and during the last 3.5 hours of exposure. No difference in HA and O-Cr excretion was found between printing trade workers and controls. The median O-Cr excretion increased 29 times during exposure, whereas the HA excretion increased only five times. Thus only 3% of the O-Cr excretion originated from other sources than toluene whereas the corresponding value for HA was 19%. Standardisation of the concentrations of HA and O-Cr in relation to urinary creatinine reduced the relative variation by 29% and 56% respectively. This was not reduced further by expressing the excretions as average excretion rates based on total volume of urine collected. Background urinary O-Cr excretion was three to four times higher among smokers than non-smokers, probably due to the content of O-Cr in cigarettes. The O-Cr excretion in unexposed smokers was, however, 10 times lower that that of the non-smokers during the end of the experimental exposure to 100 ppm toluene.

Circadian rhythms in the urinary excretion of metals and organic substances in "healthy" men

Circadian rhythms in the urinary excretion of metals and organic substances were examined in ten "healthy" men under conditions of water loading and restriction. Four characteristic rhythms were observed: (1) decreased excretion during the night for lead and urinary flow rate; (2) decreased excretion of hippuric acid, delta-aminolevulinic acid, coproporphyrin, creatinine, and total urinary solutes during the night and morning hours; (3) increased excretion of mercury and zinc during the morning hours; and (4) no significant variation for copper. Excretion of lead, hippuric acid, delta-aminolevulinic acid, and total urinary solutes was significantly correlated with urinary flow rate and creatinine excretion, which suggested that their circadian rhythms were the consequence of reduced glomerular filtration and increased reabsorption by the distal tubule and collecting duct during the night and morning hours. Similarly, it was suggested that the mercury and zinc rhythms resulted partly from increased reabsorption during the night hours; the coproporphyrin rhythm reflected reduced glomerular filtration of coproporphyrinogen during the night and morning hours.

An improved gas chromatographic determination of urinary catecholamine metabolites

We describe an improved gas chromatographic method for the determination of 3-methoxy-4-hydroxymandelic acid (vanilmandelic acid), 3-methoxy-4-hydroxyphenyacetic-acid (homovanillic acid), and 3-methoxy-4-hydroxyphenylethylene glycol. By incorporating slight modifications to established procedures, this method allows the urinary metabolites to be measured more rapidly and with better resolution. The procedure uses an internal standard and involves ethyl acetate extraction, silylation, and chromatography using a combination of two different stationary phases. The technique is simple and reliable and may be easily incorporated as a routine laboratory procedure.

Simultaneous kinetic modelling of plasma levels and urinary excretion of salicyluric acid, and the influence of probenecid

In a fundamental study on the effect of probenecid on the plasma kinetics and the renal handling of some organic anions known to be transported by the tubular secretion mechanism in the mammalian kidney, we measured plasma levels and urinary excretion rates of salicyluric acid in male Beagle dogs, after intravenous application of salicyluric acid, with and without co-administration of probenecid. The animals were anaesthetized with sodium pentobarbital (30 mg/kg) and provisions were made for blood and urine sampling. In order to obtain a sufficiently high and constant urine flow, an infusion of a solution containing 5% inulin (2 ml/min) was given throughout an experiment. Inulin was added for measurement of the glomerular filtration rate. Linear plots of the urinary excretion rate against the average plasma concentration of each urine collection period were drawn as an illustrative way to depict the relation between plasma concentration and urinary excretion rate. In order to quantify the effect of probenecid on the plasma kinetics and the renal handling of salicyluric acid, we conceived a dynamic model, able to describe changes in plasma kinetics as well as in urinary excretion. The effect of probenecid on the pharmacokinetics of salicyluric acid can be adequately described in terms of a non-competitive inhibition of the tubular secretory mechanism for salicyluric acid. Parameters for the description of this interaction were estimated by a simulation procedure with the aid of the computer program CSMP III.

Hippuric acid and o-cresol in the urine of workers exposed to toluene

Factory workers, 74 males and 56 females exposed predominantly to toluene up to 129 ppm, were examined for the urinary excretion of hippuric acid and o-cresol. The time-weighted averages (TWA) of toluene exposure were measured by personal sampling with carbon felt dosimeters. A preliminary study revealed that the concentrations of hippuric acid and o-cresol in urine increased during work and both reach their peaks at the end of the shift. Correlation coefficients between the TWA of toluene concentration in air and hippuric acid concentration in urine collected at the end of the shift were 0.803 for the 74 males, and 0.830 for the 56 females, while the counterpart correlation coefficients between toluene and o-cresol were 0.607 for the 74 males, and 0.627 for the 56 females, suggesting that hippuric acid is more reliable than o-cresol as an index of toluene exposure. In the urine samples (4 to 8 samples per subject) collected during 8-h worktime from 11 males and 13 females, the urinary levels of o-cresol increased as a function of exposure time in parallel with those of hippuric acid, and the correlation coefficients between o-cresol and hippuric acid were significant (r = 0.834 approximately 0.987; P less than 0.05) when the urine samples from the same subjects were examined. The comparison of the slopes of 24 regression lines between o-cresol and hippuric acid in urine revealed that the maximal slope was almost 8 times as large as the minimal one. From 8 female workers, five urine samples each were collected during 8-h worktime on two consecutive Mondays and analyzed for the two metabolites. The slopes of the regression lines between o-cresol and hippuric acid in the samples from the same subject were identical, regardless of variation in exposure intensity. The findings indicate that an individual difference exists in the pattern of toluene metabolism, and that the ratio between aliphatic and aromatic oxidation is presumably set congenitally. Possible toxicological significance is discussed.

Possible defect in xenobiotic activation before glycine conjugation in protein-energy malnutrition

1. [14C]Benzoic acid administered to rats fed a normal diet was excreted mainly (99% of 24h excretion) as hippuric acid. 2. In protein-energy malnourished rats, only about 74% of [14C]benzoic acid administered was excreted as hippuric acid. The remainder was excreted as the glucuronide conjugate. 3. The oxidative phosphorylation capacity of liver mitochondria of malnourished rats was 30% less than that of normal rat liver mitochondria. 4. The decreased rate in oxidative phosphorylation is discussed in relationship to the observed decrease in glycine conjugation.

Urine and tissue oxalate and hippurate levels in ethylene glycol intoxication in the dog

Oxalate, hippurate and ethylene glycol were measured in dogs given 5 ml/kg ethylene glycol orally. Eight hours after administration, oxalate levels were 7.2-9.1 ppm in renal tissue and 10-100 ppm in urine. Hippurate was 40-90 ppm in urine. Ethylene glycol was 10-100 ppm in renal tissue and 5,300-27,000 ppm in urine. The above substances were measured in urine and renal tissue from normal dogs, dogs in non-toxic renal failure and clinical cases of ethylene glycol intoxication. Urine was analyzed for ethylene glycol by gas chromatography using direct injection. Ethyl ether extraction provided good recovery of ethylene glycol from tissues and blood. Results were confirmed by gas chromatography/mass spectrometry (GC/MS). Oxalic acid (CA oxalate) was extracted with acidic methanol, methylated and analyzed by GC. Results were confirmed by GC/MS. Hippuric acid (calcium hippurate) was extracted with acidic methanol and chromatographed by thin layer chromatography (TLC). Ultraviolet spectrometry and mass spectroscopy were used to confirm the results. High performance liquid chromatography (HPLC) and TLC with densitometry were used to quantitate hippuric acid.

[Effects of physical loads on the urinary excretion of metabolites from organic solvents. Part I. Change in the urinary excretion of glycine conjugate, hippuric acids, and glycine after a physical burden]

Effects of physical loads on the excretion of urinary glycine conjugates, which are commonly used as an index of organic solvent intake, were examined. After physical exertion by Kendo exercise university students for about 2 hours, urinary protein excretion changed from the levels of (-) or (+) before the exercise to (+) to (formula: see text) after the exercise revealed by the test-tape semi-quantitative indication, and the levels of urinary creatinine increased to approximately 1.9 time and initial level. Under the present experimental conditions, the following results were obtained. 1) Statistically no significant change was observed in the levels of urinary hippuric acid, but an increasing trend was recognized. 2) The glycine levels in the urine decreased and the significance was stressed when the values were adjusted with reference to the specific gravity of urine or to the levels of urinary creatinine. 3) The ratio of hippuric acid to the glycine in the urine increased almost twice as high as the initial ratio and the physical load seemed to promote the glycine conjugation. 4) As to the adjusted levels of urinary metabolites, especially due to several organic solvents, values adjusted with reference to the specific gravity of urine and those to the levels of urinary creatinine correlated well in the samples collected before the exertion. But a poor correlation was observed in the samples collected after the exertion. Therefore, a notice should be given when the adjustment of the values with reference to the levels of urinary creatinine, which is widely used in the health administration practice for organic solvent workers to assess the levels of exposure, since the adjusted values were lowered unnecessarily by excess excretion of creatinine after the physical exertion and the tendency would be exaggerated especially under the low level exposure to organic solvent vapours in the work yard.