Benzoic acid metabolism in presence of Schistosoma mansoni infection in mice

The metabolism of benzoic acid was examined in S. mansoni infected CBA mouse. The result showed that control animals dosed with 150 mg/kg benzoic acid resulted in urinary excretion of two metabolites, hippuric acid and benzoic acid glucuronide. Administration of the same dose to animal carrying S. mansoni for a period of over 6 weeks resulted in decreased formation of hippuric acid and total elimination of benzoic acid by glucuronide pathway.

Effects of subchronic parathion administration on sodium salicylate excretion kinetics in female rats

Organophosphorus (OP) pesticides are considered to be environmental contaminants, and chronic exposure to low levels through the diet may affect drug action. To study this possible interaction, ethyl parathion was administered by intubation to female rats for 35 consecutive days at a dose of 0.05 or 0.2 mg/kg of body weight per day. At 7, 21 and 35 days after parathion was initiated, rats were administered a single dose of 20 mg/kg sodium salicylate intraperitoneally. Total salicylates, salicylic acid (SA), salicyluric acid (SU) and gentisic acid (GA) were determined in urine. At 7 days, parathion treatment slowed the excretion of total salicylates. This effect was more evident at longer treatment times. Total excretion of SA was increased at the expense of GA at 7 days. However, this effect was reversed at 21 and 35 days. Excretion of SU was drastically diminished after 21 days of treatment with parathion. The results suggest that subchronic oral administration of parathion to female rats changes the excretion kinetics of sodium salicylate through combined effects on renal excretion mechanisms and biotransformation processes. Thus, exposure to low concentrations of environmental contaminants may produce important changes in drug action.

Fibronectin turnover in the premature neonate measured with [15N]glycine

Fibronectin is a large-molecular-weight glycoprotein present on most cell surfaces and in plasma. Plasma fibronectin concentrations in neonates are lower than those in adults and a direct relationship exists between plasma concentration and gestational age. We determined the half-life and fractional synthetic rate (FSR) of plasma fibronectin in the premature infant. Infants and adults received a loading dose of [15N]glycine followed by a constant infusion [15N]glycine incorporation into plasma fibronectin and urine hippurate was determined by gas chromatography-mass spectrometry. The plasma fibronectin FSR in the preterm neonates was 15.5 +/- 9.9%/d(means +/- SD) and the half-life was 5.55 +/- 2.25 d. Birth weight correlated inversely with plasma fibronectin half-life. In the adults the plasma fibronectin FSR ranged from 20 to 87%/d and half-life ranged between 0.79 and 3.47 d. These data suggest that decreased plasma fibronectin levels in preterm infants are due to reduced FSRs rather than to greater turnover of a relatively small plasma pool.

Excretion of hippuric acid during sodium benzoate therapy in patients with hyperglycinaemia or hyperammonaemia

In patients with non-ketotic hyperglycinaemia and two patients with urea cycle disorders treated with varying doses of sodium benzoate there was linear correlation between intake of benzoate and excretion of hippurate. Patients with non-ketotic hyperglycinaemia excreted significantly more benzoate in the form of hippurate than patients with urea cycle disorders (74 +/- 7.0 vs 41 +/- 3.6%). The plasma concentration of glycine decreased following benzoate treatment only in the patients with non-ketotic hyperglycinaemia. The observed difference between the two groups in the excretion of hippurate seems to support the concept that glycine availability may be limiting in benzoate therapy for some patients.

[Method for simultaneous determination of six metabolites of toluene, xylene and ethylbenzene, and its application to exposure monitoring of workers in a printing factory with gravure machines]

For the biological monitoring of exposure to solvent composed of toluene, xylene, and ethylbenzene used in a printing factory with gravure machines, we developed a HPLC method for the simultaneous determination of urinary metabolites of this solvent, i.e. hippuric acid, o-, m-, and p-methylhippuric acid, mandelic acid and phenylglyoxylic acid. Except for phenylglyoxylic acid, urinary concentrations of the metabolites determined by the present method correlated well with the air concentrations of the respective solvent components. Hence the present method is useful in monitoring solvent exposure. In 91 workers of the printing factory and 53 control subjects, we also determined the concentrations of some phenolic metabolites and confirmed that o-cresol is a useful indicator for monitoring toluene exposure.

Influence of cigarette smoking on the toxicokinetics of toluene in humans

To study the influence of cigarette smoking on the toxicokinetics of toluene, 10 habitual smokers who intended to stop smoking were exposed to toluene vapor (3.2 mmol/m3, 4 h) at three different exposure occasions: (I) while the smoking habit was still ongoing, and (II and III) 1 and 3-4 wk, respectively, after the day at which the smoking habit was discontinued. Solvent concentrations in the exhaled air and in the blood as well as hippuric acid concentrations in the urine were measured during the exposure period and for 3 h after the exposure period. The apparent clearance of toluene decreased significantly (p less than 0.05) 3-4 wk after the smoking habit was discontinued. This decrease was not a consequence of the increased body weight noticed in the subjects. No statistically significant differences between the three exposure occasions in the elimination rate of hippuric acid could be demonstrated. Thus, cigarette smoking seems to enhance the elimination rate of toluene from the body, since the apparent clearance was decreased after smoking was stopped.

Simultaneous determination of urinary creatinine and metabolites of toluene, xylene, styrene, ethylbenzene and phenol by automated high performance liquid chromatography

An attempt was made to establish a method for the direct determination of urinary concentrations of creatinine, hippuric acid, methylhippuric acid and mandelic acid by automated high performance liquid chromatography (HPLC). Urine was diluted with distilled water or mobile phase, then the mixture was centrifuged and the supernatant was injected into HPLC. A stainless-steel column packed with octadecyl silanized silicate was used, and the mobile phase was a solution of [20 mM potassium phosphate monobasic containing 3 mM sodium 1-decanesulfonate]/acetonitrile (85/15). Another HPLC method for the determination of urinary concentration of phenol, metabolites of benzene and/or phenol is also described. Phenyl sulfate and phenyl glucuronide in urine were hydrolyzed enzymatically into phenol. The hydrolyzed mixture was injected into HPLC with the ODS column. The mobile phase was a solution of [20 mM potassium phosphate monobasic containing 1 mM sodium 1-decanesulfonate]/acetonitrile (85/15). The ratio of hippuric acid (HA) concentration to creatinine concentration determined by the urine of students after physical exercise was similar to that before exercise. Moreover, the coefficient of correlation found between the toluene concentration in a workshop and the HA concentration in workers' urine, corrected for creatinine, was higher than that obtained between the toluene concentration and the uncorrected HA concentration. For assays on stored urine samples, urine was spotted on filter paper, dried and kept several weeks, and then MA, HA, o-MHA, m-MHA and creatinine in the filter paper were eluted with 50% methanol and their concentrations determined by HPLC.

Neurotoxic effects of solvent exposure on sewage treatment workers

Nineteen Sewage Treatment Workers (STWs) exposed to industrial sewage that contained benzene, toluene, and other organic solvents at a primary sewage treatment plant in New York City (Plant A) were examined for evidence of solvent toxicity. Fourteen (74%) complained of central nervous system (CNS) symptoms consistent with solvent exposure, including lightheadedness, fatigue, increased sleep requirement, and headache. The majority of these symptoms resolved with transfer from the plant. Men working less than 1 yr at Plant A were more likely to complain of two or more CNS symptoms than men who were working there longer than 1 yr (p = .055). Objective abnormalities in neurobehavioral testing were found in all 4 men working longer than 9 yr at this plant, but in only 5 of 15 employed there for a shorter period (p = .03). These results are consistent with the known effects of solvent exposure. Occupational health personnel must be aware that STWs can be exposed to solvents and other industrial wastes.

Toluene abuse and renal tubular acidosis in pregnancy

Five gravidas presented with severe renal tubular acidosis from paint sniffing. Normal acid-base balance returned within 72 hours with cessation of toluene abuse and standard supportive measures. Fetal heart tracings and dynamic ultrasound parameters were normal in four of five cases. Three of five infants were growth-retarded at birth; two showed anomalies and neonatal hyperchloremic acidosis. These and previous cases of renal tubular acidosis in pregnancy suggest that toluene is teratogenic.

Determination of benzoic acid and hippuric acid in human plasma and urine by high-performance liquid chromatography

For patients with inborn errors of urea synthesis, oral administration of sodium benzoate is the usual treatment to increase the nitrogen excretion. Thus, monitoring hippuric acid and benzoic acid simultaneously in human biological fluids is considered to be clinically important. We developed a simple and accurate high-performance liquid chromatographic method for the simultaneous determination of hippuric acid and benzoic acid in human plasma and urine. This method requires no extraction step. Aliquots of urine and plasma are added to a solution of internal standard (o-chlorobenzoic acid) in acetonitrile and directly injected onto a reversed-phase column using an acidic (pH 2.7) eluent and ultraviolet detection at 235 nm. The preliminary plasma concentration-time and urinary excretion rate-time profiles of hippuric acid and benzoic acid from a healthy subject receiving small, medium and large doses of sodium benzoate are reported.

Possible genetic influence on conjugate formation in salicylic acid metabolism

Subjects (7 males and 7 females) were dosed with salicylic acid (1 g) and hourly urinary samples were analyzed for its metabolites. The results obtained showed that the female subjects had higher capacity for salicylurate formation than the male (P less than or equal to 0.025). The urinary hourly excretion ratio of salicylurate and salicylglucuronic acid was about or greater than 1 while in the male this ratio is less than 0.50. A comparison of this ratio between female and male showed a highly significant difference (P less than or equal to 0.001). The high capacity of glucuronic acid pathway in male and the alternate pathway in female suggest a possible genetic influence in salicylic acid metabolism.

On the mechanism of toluene-induced renal tubular acidosis

This study was aimed to investigate the pathogenesis of toluene-induced renal tubular acidosis (RTA). In 5 individuals addicted to toluene sniffing we documented the occurrence of hypokalemia and hyperchloremic metabolic acidosis associated with inability to lower urine pH below 5.5 (6.06 +/- 0.24). Overall kidney bicarbonate reabsorption was normal or enhanced, a feature characteristic of the distal form of RTA (DRTA). These findings resemble those found during the administration of amphotericin B, a drug felt to cause DRTA by increasing hydrogen ion (H+) back-diffusion in the collecting tubule. In toluene sniffers, the urine pCO2 measured in a highly alkaline urine was reduced (47 +/- 8.8 mm Hg), suggesting a decrease in the rate of collecting tubule H+ secretion rather than H+ back-diffusion. To investigate these two mechanisms of altered distal acidification more directly we studied the effect of toluene on acidification by the urinary turtle bladder, an epithelial analogue of the mammalian collecting tubule. In this preparation, toluene resulted in a decrease in the rate of H+ secretion measured by either the pH stat technique or the reverse short circuit current. When mucosal pH was progressively lowered to examine H+ secretion against an H+ gradient, toluene-treated bladders displayed a significant decrease in proton conductance but the lowest mucosal pH required to nullify H+ secretion, (MpH) JH = O, was not different from that of control bladders (4.05 +/- 0.29 and 3.90 +/- 0.13, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Mutual metabolic suppression between benzene and toluene in man

The exposure intensity during a shift and the metabolite levels in the shift-end urine were examined in male workers exposed to either benzene (65 subjects; the benzene group), toluene (35 subjects; the toluene group), or a mixture of both (55 subjects; the mixture group). In addition, 35 non-exposed male workers (the control group) were similarly examined for urinary metabolites to define background levels. A linear relationship was established between the intensity of solvent exposure and the corresponding urinary metabolite levels (i.e. phenol, catechol and quinol from benzene, and hippuric acid and o-cresol from toluene) in each case when one of the three exposed groups was combined with the control group for calculation. Comparison of regression lines in combination with regression analysis disclosed that urinary levels of phenol and quinol (but not catechol) were lower in the mixture group than in the benzene group when the intensities of exposure to benzene were comparable, indicating that the biotransformation of benzene to phenolic compounds (excluding catechol) in man is suppressed by co-exposure to toluene. Conversely, metabolism of toluene to hippuric acid was suppressed by benzene co-exposure. Conversion of toluene to o-cresol was also reduced by benzene, but to a lesser extent. The significance of the present findings on the mutual suppression of metabolism between benzene and toluene is discussed in relation to solvent toxicology and biological monitoring of exposure to the solvents.

Urinary hippuric acid excretion after use of spray ski-wax and remover

The biological monitoring for exposure to toluene is based on the measurement of urinary hippuric acid concentration (HA-U). In occupational health, workers exposed to toluene are examined for HA-U, because collection of urine samples is easy. The HA-U data of an engineer who did not use toluene occupationally showed relatively high values. It was indicated that he went to ski every weekend in winter and had used spray ski-wax and remover which contained toluene. The ski-club members of Tokai University, School of Medicine who used such sprays were examined for HA-U at the ski training camp. It was revealed that the use of these sprays elevated the HA-U values remarkably. Therefore, the use of sprays, especially in the winter season, can be one of confounding factors for biological monitoring of occupational exposure to toluene based on measurement of HA-U.

Changes in the excretion of endogenous glycine conjugate as a possible artifact in toxicological experiments

Changes in the urinary excretion of hippuric acid (HIA) and phenaceturic acid (PUA) as well as their metabolic precursors, i.e. benzoic (BA) and phenylacetic acid (PAA), in rats housed in glass metabolic cages for 4 days were monitored using gas-liquid chromatography. The amount of HIA excreted was 128 +/- 63 mumol/kg for female and 79 +/- 43 mumol/kg for male rats in the first 24 h and decreased to 11 +/- 7 mumol/kg (p less than 0.01) for female and 3.2 +/- 2.4 mumol/kg (p less than 0.001) for male rats on the 2nd day. These values remained nearly at the same level until the end of the experiment. The amount of PUA decreased from 48 +/- 12 mumol/kg on the 1st day to 22 +/- 9 mumol/kg (p less than 0.05) on the 2nd day by male rats, whereas by the females the decrease from 30 +/- 9 mumol/kg to 21 +/- 8 mumol/kg was not significant. The decrease in the excretion of glycine conjugates was compensated by a parallel increase in the level of unconjugated BA and PAA.

Urinary excretion of 5-oxoproline (pyroglutamic aciduria) as an index of glycine insufficiency in normal man

1. The evidence is accumulating to suggest that glycine, the simplest amino acid, is conditionally essential in man. Benzoic acid, by conjugation with glycine to form hippuric acid, is known to deplete the free glycine pool of the body. Glycine is one substrate for the enzyme glutathione synthase (EC 6.3.2.3) and in the inborn error of metabolism in which glutathione synthase function is defective, increased quantities of 5-oxoproline are excreted in the urine. 2. An oral dose of 4-10 g sodium benzoate was given to six normal adults to deplete the metabolic pool of glycine, and the urinary excretion of 5-oxoproline was followed for 6 h. In five of the six, a significant increase in the urinary 5-oxoproline was seen within 3 h. 3. These findings show that 5-oxoprolinuria can result from limited glycine availability, and may provide a useful test for assessing glycine sufficiency in a range of physiological and pathological states.

A study on the health hazard of toluene in the polythene printing industry in Singapore

A study was conducted to determine if there were any health effects among the polythene printers who were exposed to toluene and to evaluate the use of urinary hippuric acid in biological monitoring. The study covered 54 printers from 6 plants out of the universe population of 32 polythene printing plants who used toluene as ink dilutants. They were matched with 54 controls for age, sex, race and similar occupational status. All were interviewed and examined clinically. 23 patients were selected for neurobehavioural tests. 26% of the printers had more than 10 years of exposure to toluene. No case of clinical encephalopathy or peripheral neuropathy was detected. 38.9% of the printers had hand dermatitis compared with 1.9% among the controls. Results of the neurobehavioural tests for the 23 printers were not statistically different from the controls. The results of the liver function test were within normal limits. The mean toluene-in-air level was 246 +/- 25 mg/m. Mean blood toluene was 0.63 +/- 0.14 microgram/ml. The mean urinary hippuric acid was 2.83 +/- 0.48 mg/ml as compared to 0.35 +/- 0.08 mg/ml in the controls. Urine hippuric acid corrected to SG of 1.016 was well correlated to air toluene level (r = 0.81). Toluene appears not to have any significant nervous system or liver effects in these printers. Urinary hippuric acid is a useful indicator for biological monitoring of atmospheric exposure to toluene.