Takaharu Araki

Relationship between delta‐aminolevulinic acid dehydratase genotypes and heme precursors in lead workers

BACKGROUND The objective of this study was to investigate the relationships between genotypes of delta-aminolevulinic acid (ALA) dehydratase (ALAD) and disturbances in the heme biosynthetic pathway by lead exposure. METHODS The subjects were 192 male lead workers and 125 control subjects. Blood lead concentrations (Pb-B), plasma ALA concentrations (ALA-P), and ALAD genotypes were determined for all subjects. In lead workers, ALAD activity, ALA in urine (ALA-U), and erythrocyte zinc protoporphyrin (ZP) were also determined. RESULTS The frequency of ALAD2 (minor type of ALAD allele) was calculated to be 0.087 in all subjects. No significant relationship was found between ALAD2 frequency and Pb-B levels in lead workers. ALAD1 homozygotes showed significantly higher levels of ZP and ALA-P in comparison with those of ALAD2 carriers at Pb-B levels more than 20 microg/dL and 40 microg/dL, respectively. CONCLUSIONS ALAD1 homozygotes might be more susceptible than ALAD2 carriers to disturbances in heme metabolism caused by lead exposure.

Determination of urinary alkoxyacetic acids by a rapid and simple method for biological monitoring of workers exposed to glycol ethers and their acetates

SummaryIn control subjects and workers exposed to glycol ethers and their acetates, we determined the urinary metabolites (three alkoxyacetic acids) by a simple and rapid method. Levels of urinary metabolites were significantly higher in the solvent workers than in the nonexposed subjects. The exposure levels measured by personal monitoring of breathing zone air were far below the threshold limit value. The present results indicate that determination of urinary alkoxyacetic acids by the practical method used here is useful for evaluating excessive exposure to solvents.

Biological monitoring of workers exposed to N, N-dimethylformamide by determination of the urinary metabolites, N-methylformamide and N-acetyl-S-(N-methylcarbamoyl)cysteine

Biological monitoring of workers exposed toN,N-dimethylformamide (DMF) was carried out by determination of the urinary metabolites,N-methylformamide (MF, mainly fromN-hydroxymethylformamide) andN-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC), which were derived from two different routes of metabolism of the solvent. The urinary levels of MF increased rapidly at the start of the work shift, and decreased almost to zero within 24 h after the beginning of the last exposure. The highest level was found between the end of the afternoon shift and bedtime. AMCC levels remained constant over the consecutive work days and increased after the cessation of exposure, with the peak concentration being observed at 16–40 h after the cessation of exposure. AMCC levels at the beginning of the next morning shift were closely correlated with personal exposure levels of DMF in air, although the correlation of MF and DMF in air was highest in the urine at the end of the shift. Hence urinary AMCC represents an index of the average exposure during several preceding work days and may indicate the internal dose. By contrast, MF represents an index of daily exposure.

Gaschromatographic determination of butoxyacetic acid after hydrolysis of conjugated metabolites in urine from workers exposed to 2-butoxyethanol

For the gaschromatographic determination of total butoxyacetic acid (BAA), i.e., free plus conjugated BAA in urine, we studied the acid hydrolysis condition to cleave the conjugate. The optimum condition for hydrolysis was chosen to be 60 min boiling of the mixture of 1 ml twofold diluted urine and 1.2 ml hydrochloric acid. For the biological monitoring of workers exposed to 2-butoxyethanol (BE), we applied our acid hydrolysis method to the urine from 6 workers exposed to the solvent for 7 days and determined total BAA as well as free BAA and conjugated BAA, which was calculated as the difference between the concentrations of free and conjugated BAA. The percentages of conjugated BAA vs. total BAA varied from 44.4% to 92.2% (mean value 71.1 %) among 6 individual workers over 7 days and decreased gradually over the consecutive work days. In the latter half of the work week, free BAA comparatively accounted for the larger portion of urinary BAA. Significant correlations were found between urinary BAA concentrations and BE levels in the breathing-zone air (TWA). The correlation coefficients of urinary concentrations of total or conjugated BAA vs. BE levels was higher than that of free BAA concentrations vs. BE levels. Hence, the determination of total BAA in urine is a suitable test for the biological monitoring of BE exposure, because of the simplicity in procedures and the good agreement with BE exposure levels.

Determination of erythrocyte porphyrins by reversed-phase high-performance liquid chromatography using capsule-type silica gels coated with silicone polymer.

A simple, rapid and reliable method is described for determining erythrocyte porphyrins using a new type of reversed-phase silica whose surface is coated with silicone polymer. After a single-step extraction of blood with N,N-dimethylformamide, zinc protoporphyrin IX and protoporphyrin IX were separately quantified in a single run in 5 min. The column life was so long that no alteration in elution profile or retention time was apparent after 1500 injections of samples. The method described would be useful for the screening of lead exposure or iron-deficiency anaemia, and also for the diagnosis of erythropoietic protoporphyria.

Simple and rapid method for determining nicotinamide adenine dinucleotide synthetase activity by high-performance liquid chromatography

A method is described for the determination of nicotinamide adenine dinucleotide synthetase (NADS) activity in human blood. Using high-performance liquid chromatography (HPLC), the formed NAD is separated from the substrates and the other blood components in less than 13 min. The activity of NADS determined by HPLC is closely correlated with that determined by the conventional spectrophotometric method, which requires two steps of enzyme reaction. The present method is simple and reliable and facilitates the routine analysis of NADS activity.

尿中2,5-ヘキサンジオン(HD)のバックグランド値および作業者尿中HD濃度におよぼす加水分解条件の影響

In order to determine the optimal conditions of acid hydrolysis for urinary 2,5-hexanedione (HD) measurement, the effects of urine pH or volume of HCl added to urine and hydrolysis period were studied using gas chromatography-mass spectrometry (GC-MS). When 0.3 ml of concentrated HCl was added to 3 ml of urine, complete hydrolysis to liberate HD was attained 2 h after the start of heating at 100 degrees C for urine from non-exposed subjects. On the contrary, in urine from exposed subjects most of HD was liberated in 30 min at 100 degrees C, suggesting that the urinary substrates converted to HD by acid hydrolysis were different between exposed and non-exposed subjects. It was confirmed that hydrolysis for 2 h at 100 degrees C with 0.3 ml of concentrated HCl added to 3 ml of urine gave the most reliable levels and the greatest amounts of HD in both urine from exposed and non-exposed subjects. Reference values were determined by the hydrolysis conditions presented here. In 84 males, 52 females, and 136 with sexes combined the urinary HD levels were 0.35, 0.49, and 0.39 mg/l (geometric mean), respectively. Urinary HD levels determined without hydrolysis (free HD) were less than 0.006 mg/l in 31 control subjects examined. In urine from exposed subjects the amount of free HD was about one-fifth of the total HD (free plus conjugated HD) as determined with acid hydrolysates, although the percentage of free to total HD varied from 0.4 to 28%.(ABSTRACT TRUNCATED AT 250 WORDS)