The relationship between aryl hydrocarbon hydroxylase activity and DNA adducts measured by (32)P-postlabelling assay in lymphocytes of lung cancer patients

We have investigated the correlation between DNA adduct levels and aryl hydrocarbon hydroxylase (AHH) activity in peripheral lymphocyte samples obtained from 42 lung cancer patients. DNA adducts and AHH activity were determined by the (32)P-postlabelling technique and the fluorometric method, respectively. The mean +/- SD of DNA adduct level was 0.88 +/- 0.37 (ranged from 0.22 to 1.90) per 10(8) nucleotides. The geometric means of non-induced and 3-methylcholanthrene (MC)-induced AHH activity, as well as AHH inducibility (MC-induced AHH activity/non-induced AHH activity) were 0.029, 0.228 pmol min(-1) 10(-6) cells, and 7.776, respectively. There was no statistically significant correlation between DNA adduct levels and non-induced or MC-induced AHH activity. A tendency of positive correlation was found between DNA adduct levels and AHH inducibility for the all subjects (n = 42, r = 0.25, p = 0.11). Such a positive correlation reached statistical significance in the subjects with squamous cell carcinoma (n = 13, r = 0.70, p < 0.01). In addition, similar correlation of DNA adducts with AHH inducibility was also observed in the GSTM1 present genotype (n = 17, r = 0.44, p = 0.07) and GSTP1-AA genotype (n = 29, r = 0.37, p = 0.05) individuals. These findings suggest that DNA adduct levels are mediated by CYP1A1 enzyme, and AHH inducibility may be a more relevant indicator than specific AHH activity for explaining the variation of DNA adduct levels in lymphocytes.

Verification of the Wiedemann-Franz law in YbRh2Si2 at a quantum critical point

The thermal conductivity measurements are performed on the heavy-fermion compound YbRh(2)Si(2) down to 0.04 K and under magnetic fields through a quantum critical point (QCP) at B(c)=0.66  T∥c axis. In the limit as T→0, we find that the Wiedemann-Franz law is satisfied within experimental error at the QCP despite the destruction of the standard signature of Fermi liquid. Our results place strong constraints on models that attempt to describe the nature of the unconventional quantum criticality of YbRh(2)Si(2).

Thermoelectric response near a quantum critical point of β-YbAlB4 and YbRh2Si2: a comparative study

The thermoelectric coefficients have been measured down to a very low temperature for the Yb-based heavy-fermion compounds β-YbAlB4 and YbRh2Si2, often considered as model systems for the local quantum criticality case. We observe a striking difference in the behavior of the Seebeck coefficient S in the vicinity of their respective quantum critical point (QCP). Approaching the critical field, S/T is enhanced in β-YbAlB4, but drastically reduced in YbRh2Si2. The ratio of thermopower to specific heat remains constant for β-YbAlB4, but it is significantly reduced near the QCP in YbRh2Si2. In both systems, on the other hand, the Nernst coefficient shows a diverging behavior near the QCP. The interplay between valence and magnetic quantum criticality and the additional possibility of a Lifshitz transition crossing the critical field under magnetic field are discussed as the origin of the different behaviors of these compounds.

Decreasing urinary PAH metabolites and 7-methylguanine after smoking cessation

OBJECTIVE

Humans are exposed to various carcinogens by smoking. Urinary metabolites of polycyclic aromatic hydrocarbons (PAH), one of the major carcinogens in cigarette smoke, were measured as the environmental carcinogen exposure marker for humans. We evaluated urinary exposure markers for smoking cessation.

METHOD

In this study, we measured cigarette smoke exposure markers, such as urinary cotinine, PAH exposure markers, such as urinary 1-hydroxypyrene (1-OHP), 2-naphthol (2-NP) and 1-naphthol (1-NP), as well as a methylating chemical exposure marker, 7-methylguanine (7-MeG). The before smoking cessation levels of these markers, and the after smoking cessation levels were then compared. Eighteen subjects participated in this smoking cessation program.

RESULTS

Levels of all of four markers were found to have decreased by 19-54% after smoking cessation. Urinary cotinine, 1-OHP, 2-NP and 7-MeG levels were found to have significantly decreased after smoking cessation. There were positive correlations between cotinine and three urinary PAH markers and between 1-OHP, 2-NP and 7-MeG.

CONCLUSION

PAH metabolites were better biomarkers of smoking cessation than 7-MeG. Analyzing urinary metabolites or urinary DNA adducts is suitable for epidemiological studies.

Leukocyte 8-hydroxydeoxyguanosine and aromatic DNA adduct in coke-oven workers with polycyclic aromatic hydrocarbon exposure

OBJECTIVE

To investigate the potential for exposure to polycyclic aromatic hydrocarbons (PAHs) to induce oxidative DNA damage, we conducted a cross-sectional study in coke-oven workers employed at an iron-steel factory.

METHODS

The study population contained 119 coke-oven workers from different work areas of the oven and 38 controls. Personal information on age, employment duration, smoking habit and alcohol consumption was obtained at an interview. Leukocyte 8-hydroxydeoxyguanosine (8-OHdG) was measured by high performance liquid chromatography with electrochemical detection. Leukocyte aromatic DNA adducts as effective dose, and urinary 1-hydroxypyren as internal dose, were also measured, and used to analyze the relationship of 8-OHdG with other biomarkers for PAH exposure, tobacco smoke and alcohol consumption.

RESULTS

The leukocyte 8-OHdG revealed a wide inter-individual variation. The highest 8-OHdG level was detected in bottom-workers of the coke-oven. There were significant differences among the four different work areas ( P=0.02). We could not find significant correlation between 8-OHdG levels and urinary 1-hydroxypyrene, but a weakly positive correlation was found between 8-OHdG and leukocyte aromatic DNA adducts among all subjects (r=0.19 P=0.03). We could not observe any effect of smoking and alcohol drinking on 8-OHdG production.

CONCLUSION

We could not find clear evidence that PAH exposure induces oxidative DNA damage.

Urinary 1-hydroxypyrene in coke oven workers relative to exposure, alcohol consumption, and metabolic enzymes

OBJECTIVES

To investigate the influence of personal lifestyle--such as smoking and alcohol consumption-on urinary 1-hydroxypyrene (1-OHP) concentrations in coke oven workers exposed to polycyclic aromatic hydrocarbons (PAHs) and to evaluate the association of 1-OHP concentrations with the genetic polymorphism of several metabolic enzymes including cytochrome P-450 (CYP) 1A1 and glutathione S-tranferases (GSTs).

METHODS

The study population contained 162 coke oven workers and 58 controls employed at the largest iron and steel factory in China. Personal data were collected at the interview. 1-OHP in urine was measured with high performance liquid chromatography with fluorescence detection. Genetic polymorphisms were identified by the polymerase chain reaction (PCR) method.

RESULTS

A positive association between excretion of urinary 1-OHP and the levels of exposure to PAHs was confirmed. Those people who consumed >or=50 g/day ethanol had significantly higher 1-OHP excretion than did other coke oven workers (p<0.01). No significant difference in urinary 1-OHP was found between smokers and non-smokers, in both controls and exposed subjects. The variant homozygotes at exon 7 of the CYP1A1 gene had significantly higher urinary 1-OHP concentrations than other CYP1A1 genotypes among the exposed workers (p=0.03). There was less association between the concentrations of 1-OHP and the GSTM1, GSTP1, or GSTT1 polymorphism.

CONCLUSIONS

The present study confirmed that urinary 1-OHP is a good biomarker for exposure to PAHs. Alcohol consumption affected urinary 1-OHP excretion. The variant genotypes of the CYP1A1 gene may result in the enhancement of PAH metabolites. It is helpful to understand the role of individual susceptibility on metabolism of carcinogens. These findings suggest that the modulating effect of individual lifestyle factors or genetic nature should be considered in future studies on occupational exposure to PAHs and in evaluating the health risk from harmful chemicals.

Lymphocyte DNA adducts and polymorphism in the DNA repair enzyme XPD

The effect of genetic polymorphism of DNA repair enzyme on the DNA adduct levels was evaluated in this study. We explored the relationship between polymorphism in the nucleotide excision repair enzyme XPD and DNA adduct levels in lymphocytes. Lymphocyte DNA adducts were measured by a (32.)

Aromatic DNA adducts in coke-oven workers, in relation to exposure, lifestyle and genetic polymorphism of metabolic enzymes

OBJECTIVE

This study investigates the effect of multiple factors, including exposure to polycyclic aromatic hydrocarbons (PAHs), lifestyle, genetic polymorphism of cytochrome P450 (CYP)1A1, glutathione transferase (GST)M1, GSTP1, N-acetyltransferase (NAT)2 and gene p53, as well as any family history of cancer, on DNA adduct levels in coke-oven workers.

METHODS

Sixty-five coke-oven workers employed at the largest iron-steel factory in China were recruited for the study. Personal data were collected at the interview. DNA adduct levels in total white blood cells (WBCs) were detected using 32P-postlabeling techniques. Genetic polymorphisms were analyzed by polymerase chain reaction (PCR) methods.

RESULTS

The subjects were divided into low and high exposure groups, according to personal exposure to PAHs. The mean adduct value was 1.57 (range 0.54 to 4.35) per 10(8) nucleotides. A tendency for increased levels of DNA adducts in the high exposure group was observed, compared with the low exposure group (P = 0.07). In the low exposure group, DNA adducts were found to be positively associated with urinary cotinine (r = 0.44, P = 0.01). The rare allele homozygotes of CYP1A1 showed significantly higher DNA adduct levels than those of other CYP1A1 genotypes. Individuals with the NAT2 wild type had significantly increased DNA adduct levels than those with other NAT2 genotypes in the high exposure group. The p53 genetic polymorphism revealed a significantly positive effect on DNA adducts formation. There was a significantly higher adduct level in the subjects with a family history of cancer than those without, in the high exposure category.

CONCLUSIONS

Effects of several variables, such as smoking, genetic polymorphism of 2 CYP1A1, NAT2, and gene p53, and a family history of cancer on DNA adduct levels were found, suggesting that these variables should be considered when evaluating the genotoxic effect of occupational exposure to PAHs using WBCs DNA adducts.

Inter-individual variation of smoking-related DNA adducts in lymphocytes-relationship to mRNA levels for CYP1A1 and DNA repair enzymes

The measurement of DNA adducts is a useful indicator for environmental carcinogen exposure monitoring. To clarify the effect of metabolic activation and DNA repair system on the inter-individual variation of DNA adduct levels, aromatic DNA adducts and mRNA expression of metabolic and repair enzymes were measured in 43 human lymphocytes. Aromatic DNA adducts were measured by the nuclease P1 postlabelling method. The metabolic activation enzyme; cytochrome P4501A1 (CYPIA1), and the repair enzyme; excision repair cross complimenting gene (ERCC1), and the xeroderma pigmentosum C group cell gene (XPCC), mRNA expression were measured by the reverse transcription-PCR method. The mean adduct levels were 1.01 ± 0.49 in 43 subjects. There was a positive correlation between DNA adducts and CYP1A1 mRNA (r = 0.33, p = 0.12). DNA adduct levels had a positive correlation with ERCC1 (r = 0.35, p = 0.03) and a negative correlation with XPCC mRNA levels (r = -0.28, p = 0.07). We found Brinkman index, CYP1A1 genotypes, CYP1A1 mRNA and XPCC mRNA as a predictor for log DNA adduct levels in multivariate analysis. Metabolic activation and the repair system may explain the inter-individual variation of DNA adducts in lymphocytes.

Effects of genetic polymorphism of metabolic enzymes, nutrition, and lifestyle factors on DNA adduct formation in lymphocytes

Although cigarette smoking is one major determinant of lung carcinogenesis, not all smokers develop cancer. This phenomenon is due to individual variation in genetic susceptibility to carcinogens, nutrition, and lifestyle. Previous studies have shown that genetic polymorphism of metabolic enzymes and plasma micronutrients are associated with lung cancer risk. DNA adducts may serve as a molecular dosimeter for exposure to carcinogens. In this cross-sectional study, we analyzed the blood samples of 158 subjects to evaluate the effects of polymorphisms of cytochrome P450 1A1 (CYP1A1), glutathione S-transferase M1 (GSTM1), T (GSTT), N-acetytransferase 2 (NAT2), and aldehyde dehydrogenase 2 (ALDH2) as well as the effects of plasma beta-carotene and alpha-tocopherol on lymphocyte DNA adducts measured by 32P-postlabeling analysis. The DNA adduct level of smokers (mean +/- SD, 1.26 +/- 0.79/10(8) nucleotides) was significantly higher than that of nonsmokers (0.87 +/- 0.33, P = 0.007). Smokers with CYP1A1 minor homozygotes and GSTM1 null genotypes had a significantly higher level of DNA adducts than those without (P = 0.027 for homozygotes, P = 0.049 for heterozygotes). Smokers with NAT2 minor homozygotes also tended to have a higher DNA adduct level than those with heterozygotes and wild alleles, but the difference was not statistically significant. The DNA adduct level of smokers with ALDH2 heterozygotes was significantly higher than that of smokers with minor homozygotes (P = 0.045). When smokers were divided into "high" and "low" groups according to mean level of plasma beta-carotene or alpha-tocopherol, in the low beta-carotene group, the subjects with CYP1A1 minor homozygotes had higher DNA adduct levels than those with other CYP1A1 genotypes. Smokers with GSTT null genotype and high beta-carotene tended to have a higher DNA adduct level than those with GSTT present and high beta-carotene (P = 0.07), and those with GSTT null genotype and low beta-carotene (P = 0.07). There was weak correlation between DNA adduct level and number of cigarettes smoked per day in the low plasma beta-carotene group (r = 0.28, n = 36, p < 0.1). These results suggested that polymorphisms of CYP1A1, GSTM1, T, NAT2, and ALDH2, and plasma beta-carotene may modulate the level of DNA adducts.

Evaluation of organic solvent-induced inflammation modulated by neuropeptides in the abdominal skin of hairless rats

In this study, the severity and time course of inflammation induced by 4 organic solvents (acetone, cyclohexane, toluene and m-xylene), and the effect of neuropeptides during the inflammation were investigated in the hairless rat abdominal skin. Plasma extravasation used as a parameter of inflammation was measured by Evans blue and 125I-bovine serum albumin (BSA). Total volume of plasma extravasation induced by 4 organic solvents in 240-min exposure was as follows: toluene > m-xylene > cyclohexane > acetone = 0. While hydrophobic solvents (toluene, m-xylene, cyclohexane) induced plasma extravasation, the hydrophilic solvent, acetone, did not induce plasma extravasation. It was suggested that the severity and time course of plasma extravasation depend on chemical characteristics of the organic solvents. In immunohistochemical study, substance P (SP)-immunoreactive nerve fibers (IRNF) and calcitonin gene-related peptide (CGRP)-IRNF were intact during 240-min exposure to acetone. In contrast, cyclohexane, toluene, and m-xylene reduced the number of SP-IRNF and CGRP-IRNF in 10 min exposure and further reduced immunoreactivity. In hairless rats treated with systemic capsaicin, the above plasma extravasation was significantly reduced, along with SP-IRNF and CGRP-IRNF; however, protein gene product 9.5 (PGP 9.5)-IRNF was nearly intact. These results indicated that certain organic solvents induce instance of inflammation that vary widely in terms of their severity and time course, and that these differences are correlated with neuropeptides.

Relationship between plasma concentrations of beta-carotene and alpha-tocopherol and life-style factors and levels of DNA adducts in lymphocytes

beta-Carotene and alpha-tocopherol have been thought to reduce risk of lung cancer. Whether beta-carotene and alpha-tocopherol influence human DNA adducts, indicators of biologically effective doses of carcinogens, has been seldom studied. In this cross-sectional study, we measured plasma beta-carotene and alpha-tocopherol in 192 healthy men and DNA adducts in lymphocytes in 104 of the subjects. Because genetic polymorphism of cytochrome P-4501A1 (CYP1A1) and glutathione S-transferase M1 (GSTM1) has been associated with interference in formation of reactive intermediates and detoxification of polycyclic aromatic hydrocarbons, we also obtained data concerning genetic polymorphism of CYP1A1 and GSTM1. In multiple regression analysis, parameters such as alcohol consumed per day, high-density lipoprotein cholesterol, Quetelet index, and cigarettes smoked per day were correlated inversely, whereas age, plasma alpha-tocopherol, and intake frequency of fruits were correlated positively with plasma beta-carotene concentration. DNA adduct levels of high plasma beta-carotene or alpha-tocopherol groups were not significantly different from the DNA adduct levels of low plasma beta-carotene or alpha-tocopherol groups among current smokers or nonsmokers. In variant states of CYP1A1 or GSTM1 polymorphism, after controlling for effect of cigarettes smoked per day, no significant correlation was found between plasma beta-carotene or alpha-tocopherol and DNA adduct levels. These results indicated that alcohol consumption, cigarette smoking, and plasma alpha-tocopherol have a close relationship with plasma beta-carotene. The plasma beta-carotene and alpha-tocopherol were not likely to influence the level of DNA adducts in lymphocytes.

Chronic lead exposure may inhibit endothelium-dependent hyperpolarizing factor in rats

We designed experiments to determine the effect of chronic lead exposure on endothelium-dependent responses to acetylcholine (Ach) in rat isolated blood vessels. Male Wistar rats were maintained for 1 or 3 months with or without oral lead administration. Membrane potential and isometric tension were measured in mesenteric arteries. Ach caused concentration- and endothelium-dependent relaxation in rings with endothelium contracted with phenylephrine (PE). There was no significant difference in relaxation between lead-exposed and control animals. In the presence of NG-nitro-L-arginine methyl ester (L-NAME), both endothelium-dependent hyperpolarization and relaxation to Ach were significantly reduced in animals from the 3-month lead-exposed group. In aorta from lead-exposed groups, endothelium-dependent relaxation to Ach was not significantly different from that of age-matched controls, whereas both were completely inhibited in the presence of L-NAME. The basal levels of cyclic GMP in the aorta were not affected by lead exposure regardless of duration. These data indicate that both endothelium-dependent hyperpolarization and L-NAME-resistant relaxation decrease with chronic lead exposure in rat mesenteric arteries and suggest that lead is an inhibitor or endothelium-derived hyperpolarizing factor (EDHF).

Comparison between males and females with respect to the porphyrin metabolic disorders found in workers occupationally exposed to lead

To elucidate the sex difference in porphyrin metabolic disorders induced by lead exposure, we determined plasma delta-aminolevulinic acid (ALA), urinary ALA, and urinary coproporphyrin (CP) in 298 lead-exposed workers (160 males and 138 females), and compared the data thus obtained. The use of fluorometric high-performance liquid chromatography (HPLC) method which is highly sensitive and specific made possible the measurement of ALA in a small volume (50 microliters) of plasma. The concentrations (mean +/- SD) of lead in blood (males: 55.1 +/- 12.9 micrograms/dl; females: 54.7 +/- 13.5 micrograms/dl) indicated that the intensity of occupational exposure to lead was almost equal in the two groups. However, the elevation of plasma ALA concentration and the increased urine ALA and CP excretion among these lead workers were much higher in females than in males, confirming the finding of a sex difference in the biological effect of human exposure. The difference in urine CP excretion was especially pronounced, the mean concentration of urinary CP in the female workers being 3.5-5 times higher than that in the male workers.

Fluorometric HPLC determination of delta-aminolevulinic acid (ALA) in the plasma and urine of lead workers: biological indicators of lead exposure

A fluorometric high-performance liquid chromatographic (HPLC) method was developed for the highly sensitive measurement of delta-aminolevulinic acid (ALA) in biological materials. By using this method, we determined ALA in the plasma and urine of 418 workers occupationally exposed to lead and in the plasma and urine of 227 controls. The concentrations of ALA in the plasma and urine of lead workers were significantly elevated as compared with those of the controls. The concentration of ALA in plasma and urine was highly correlated with that of lead in blood in lead workers. It was found that the correlation (r = 0.742) between log of plasma ALA concentrations and blood lead concentrations in lead workers was similar to that (r = 0.711) between log of urine ALA concentrations and blood lead concentrations. These results demonstrated that the measurement of ALA in plasma or in urine using a fluorometric HPLC method was useful for the biological monitoring of lead workers.

[Metabolic fate of porphyrin and its precursors in porphyria and porphyrinuria]

The metabolic fate of porphyrins and its precursors in porphyria and porphyrinuria is discussed to understand their excretion into the feces or urine. Eight enzymes play important roles in the porphyrin pathway. An enzymatic defect at each step of heme synthesis will induce each typical form of porphyria with the exception of the first enzyme. Each porphyria is described according to the enzyme in the heme biosynthetic sequence. Lead, which disturbs two enzymes involved in the heme biosynthesis, is one of typical chemicals inducing porphyrinuria. Lead porphyrinuria is also described according to the enzymes in the pathway. The figure of porphyrin pathway, drawn in details in the present chapter, will make it easier to understand the heme biosynthetic pathway related to porphyria or porphyrinuria.

[Delta-Aminolevulinic acid in urine (screening method)]

Various methods for determining urinary delta-aminolevulinic acid (ALA) have been devised by many investigators since 1956. This paper introduces a history of the methodology in the determination of urinary ALA and application of some methods. These methods can be divided into two groups; one group consists of colorimetric methods based on the color reaction of ALA-pyrrole with Ehrlich's reagent, and the other group consists of fluorometric methods, based on the fluorescence derivatization of ALA and its separation by HPLC. Colorimetric methods are convenient and inexpensive, while these are less specific. On the other hand, the fluorometric HPLC methods are highly sensitive and specific, while these are expensive because of the high cost of the instruments.

The in vitro effect of 13 metals on the activity of erythrocyte pyrimidine 5'-nucleotidase (P5N)

The in vitro effect of 13 metal ions on the activity of erythrocyte pyrimidine 5'-nucleotidase (P5N) was investigated. Particular metals belonging to the boron group have recently been used as materials in a semi-conductor manufacturing. Of these metal ions, Ga exhibited no inhibition of erythrocyte P5N, while in extensively inhibited the erythrocyte P5N activity at concentrations of 10(-4) to 10(-3) M. In addition, the activity of erythrocyte P5N was inhibited by 90-96% when the metal ions such as Cu, Ag, Cd, Hg or Pb were added to the incubation mixture at concentrations of 10(-4) to 10(-3) M. On the other hand, there was no difference between sulfate and nitrate in the in vitro effect of the metal ions on the activity of erythrocyte P5N.

Postlabeling analysis of DNA adducts in white blood cells from lead smelter workers

We analyzed DNA adducts levels in white blood cells from 14 lead smelter workers for the first time as an indicator of the effect of lead exposure and compared with some lead exposure indices to evaluate whether lead exposure induces DNA adducts significantly. DNA adducts were measured by the nuclease P1 enhanced 32P-postlabeling method. As the lead exposure indices, we chose blood lead (Pb-B), urinary delta-aminolevulinic acid (ALA) and erythrocyte protoporphyrin (FEP). The levels of DNA adducts had a weak positive correlation with urinary ALA concentration (r = 0.62), but not significant correlation with Pb-B and FEP. This result suggests that lead exposure might have the effect to remain DNA adducts. The inhibition of DNA repair system may be one reason. This preliminary study need be followed by extended surveys on lead exposure.

Urinary N-acetyl-beta-D-glucosaminidase and beta-aminoisobutyric acid in workers occupationally exposed to metals such as chromium, nickel, and iron

To examine the relationships between the urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG) and beta-aminoisobutyric acid (AIBA) as a metabolite of thymine, and exposure to chromium, nickel, and iron, we determined these parameters in 58 workers engaged in the cutting and grinding of stainless steel or iron-steel plates. A significant increase in urinary NAG activity or urinary AIBA excretion was found in some of these workers. However, we could not find a significant positive correlation between the urinary excretion of NAG or AIBA and the urinary concentration of chromium, nickel, or iron as an indicator of internal dose.

Interrelation between urinary delta-aminolevulinic acid (ALA), serum ALA, and blood lead in workers exposed to lead

Using a fluorometric HPLC method, we determined delta-aminolevulinic acid (ALA) in sera and urine samples from 16 lead workers with blood lead levels ranging from 19 to 107 microG/100 ml. The concentration of ALA in serum correlated highly with the urinary ALA concentration (gamma = 0.957 for ALA mg/1; gamma = 0.967 for ALA mg/g creatinine). The ALA concentrations in the serum of lead workers ranged from 11 to 151 micrograms/1 with a mean of 51 micrograms/1. In addition, the concentrations of urinary ALA (mg/g creatinine) and serum ALA micrograms/1) had a strong correlation with blood lead concentrations (gamma = 0.838 and 0.892, respectively). These data indicate that the measurement of serum ALA, as well as urinary ALA, is very useful for the biological monitoring of occupational lead exposure.

Urinary excretion of 3,4-dimethylhippuric acid in workers exposed to 1,2,4-trimethylbenzene

The urinary excretion of 3,4-dimethylhippuric acid (34DMHA), a 1,2,4-trimethylbenzene (124TMB) metabolite, was investigated in workers exposed to 124TMB vapor. The time-weighted average of exposure to 124TMB was determined with a diffusive sampler. For biological monitoring of exposure, urine samples were collected from individual workers and analyzed for metabolites by high-pressure liquid chromatography. The concentration of urinary 34DMHA had a positive correlation with the level of exposure to 124TMB (r = 0.72). The data suggest that 34DMHA is one of the useful indicators for biological monitoring of 124TMB exposure.

Erythrocyte nucleotides in lead workers

We determined erythrocyte nucleotides levels in 22 lead workers with blood lead ranging from 8 to 78 micrograms/dl. Their erythrocyte pyrimidine 5'-nucleotidase (P5N) activity ranged from 19.4 to 3.4 mumol uridine/h per g hemoglobin. A significant elevation of erythrocyte pyrimidine nucleotides was found, and their contents correlated inversely with erythrocyte P5N activity and positively with blood lead concentration. In particular, the contents of uridine triphosphate (UTP) and cytidine triphosphate (CTP) exhibited a high correlation with P5N activity (r = -0.56, -0.54). However, its concentration in lead workers was estimated to be much lower than that in hereditary P5N deficiency.

Elevated urinary excretion of beta-aminoisobutyric acid and delta-aminolevulinic acid (ALA) and the inhibition of ALA-synthase and ALA-dehydratase activities in both liver and kidney in mice exposed to lead

Urinary excretion of beta-aminoisobutyric acid (ABA) and delta-aminolevulinic acid (ALA) was investigated in mice exposed to lead (500 p.p.m.) in drinking water for 14 days. Concentrations of both urinary ABA and urinary ALA increased significantly in the lead-exposed mice. However, the degree of increasing excretion was higher in urinary ALA (10-fold of the control) than in urinary ABA (2-fold of the control). On the other hand, it was demonstrated that ALA dehydratase in liver and kidney is inhibited by exposure to lead, while ALA synthase in these tissues has no inhibitory effect.

Fluorimetric determination of hepatic delta-aminolevulinic acid synthase activity by high-performance liquid chromatography

A fluorimetric method for measuring the activity of delta-aminolevulinic acid synthase (ALAS) in the liver of mice has been developed. The liver homogenate was used as the enzyme source. The final concentration of glycine (substrate) used for the assay was 100 mM. The delta-aminolevulinic acid (ALA) formed during incubation was converted into a highly fluorescent derivative by condensation with acetylactone and formaldehyde (application of the Hantzsch reaction). This derivative was completely separated from other fluorescent substances in the reaction medium, and it was determined using a high-performance liquid chromatograph equipped with a fluorescence monitor (370/460 nm). The activity of ALAS was expressed as nmol ALA formed per gram liver per hour.

Tolerance to lead-induced porphyrin metabolic disorders following lead pretreatment in mice

The protective effect of pretreatment with lead on lead-induced toxicity was investigated in mice, using some biological parameters such as urinary excretion of delta-aminolevulinic acid (ALA) and coproporphyrin, accumulation of erythrocyte protoporphyrin and inhibition of erythrocyte delta-aminolevulinic acid dehydratase; these are useful indicators for evaluating the effects on health of lead. It was demonstrated that pretreatment with a single intraperitoneal dose of 2 mg Pb/kg, 7 days prior to the challenge dose, prevents in part the increasing excretion of urinary ALA induced by a challenge exposure to lead (200 ppm) in the drinking water for 7 days.

Effect of lead on the activity of erythrocyte porphobilinogen deaminase in vivo and in vitro

The effect of lead on the activity of erythrocyte porphobilinogen deaminase (PBGD) in vivo and in vitro was investigated using blood specimens obtained from controls and lead-exposed workers. When lead nitrate was added to the incubation mixture at a final concentration of 10(-4) M, 83% inhibition of erythrocyte PBGD activity was found. However, in workers occupationally exposed to lead, no inhibition of erythrocyte PBGD activity was detected. This finding indicates that the erythrocyte PBGD test is not useful for evaluating exposure to lead in workers. In addition, the in vitro study confirmed that mercuric chloride strongly inhibits erythrocyte PBGD activity.

Studies on erythrocyte pyrimidine 5'-nucleotidase (P5N) test and its evaluation in workers occupationally exposed to lead

An erythrocyte pyrimidine 5'-nucleotidase (P5N) test was performed for 171 workers occupationally exposed to lead. Erythrocyte P5N activity was markedly inhibited by exposure to lead. Among several biological indicators (erythrocyte P5N, delta-aminolevulinic acid dehydratase (ALAD), protoporphyrin (PROTO), urinary delta-aminolevulinic acid (ALA), coproporphyrin (COPRO)), the P5N activity had the highest correlation with the concentration of lead in blood (r = -0.77). A significant inhibition of erythrocyte P5N was found in groups of lead workers with blood-lead levels of more than 10 to 19 micrograms/dl. This P5N inhibition started before any changes occurred in urinary ALA and COPRO. A 45 to 50% inhibition of P5N corresponded to the blood-lead value (50 micrograms/dl) of the BEI recommended by ACGIH. In some lead workers, erythrocyte nucleotides (mainly CTP and UTP) were determined. The data indicated that a marked accumulation of these nucleotides had occurred, and their levels correlated negatively with P5N activity and positively with blood lead.

Effect of lead exposure on some biological indices related to porphyrin metabolism and the activity of erythrocyte pyrimidine 5'-nucleotidase in the mice

The urinary excretion of delta-aminolevulinic acid (ALA) and coproporphyrin (CP) isomers (I and III) was investigated in mice exposed to lead in drinking water (200 and 500 ppm) for 14 or 30 days. Furthermore, the inhibition of pyrimidine 5'-nucleotidase (P5N) and delta-aminolevulinic acid dehydratase (ALAD) was studied in the same mice. In the lead-exposed mice, urinary excretion of ALA was significantly elevated (12-times control), while that of CP remained unchanged. This discrepancy on the urinary excretion may be of interest. The P5N activity in both erythrocytes and bone marrow cells was significantly inhibited by exposure to lead. However, the degree of inhibition was greater in the erythrocytes (45% inhibition) than in the bone marrow cells (25% inhibition). The inhibition of ALAD was much higher in erythrocytes (90% inhibition) than in liver (20-40% inhibition). The increase in erythrocyte protoporphyrin and the decrease in both hemoglobin and hematocrit were not observed in mice exposed to lead under the above conditions.

Comparison between the fluorometric HPLC method and the conventional method for determining urinary delta-aminolevulinic acid and coproporphyrin as indices of lead exposure

Fluorometric methods for determining delta-aminolevulinic acid (ALA) and coproporphyrin (CP) in urine have been recently developed by using high-performance liquid chromatography (HPLC). In the present study, urinary ALA and CP in lead-exposed workers were determined with these fluorometric HPLC methods and the conventional methods, and the results obtained were compared. In lead workers with a urinary ALA greater than or equal to 5 mg/l, the values obtained with the fluorometric HPLC method corresponded well with those measured with the conventional colorimetric method. In contrast, in lead workers with ALA less than 5 mg/l, ALA values obtained with the fluorometric HPLC method were lower than those measured with the conventional method, suggesting the possibility of matrix interference in urine. The urinary CP values obtained with the conventional method of Rimington (1971) were higher than those measured with the fluorometric HPLC method, though the correlation was good.

Relationship between inhibition of erythrocyte pyrimidine 5'-nucleotidase activity and biological response for porphyrin metabolism in workers occupationally exposed to lead

A rapid determination of erythrocyte pyrimidine 5'-nucleotidase (P5N) activity in lead workers was carried out using a high-performance liquid chromatograph (HPLC). The P5N activity had a good negative correlation with the concentration of lead in blood (PbB) ranging from 16 to 96 micrograms/dl (r = -0.82, n = 77). Further, the P5N was compared with other biological parameters: erythrocyte delta-aminolevulinic acid dehydratase (ALAD) activity, erythrocyte protoporphyrin (PROTO), urinary delta-aminolevulinic acid (ALA) and urinary coproporphyrin (COPRO). The correlation coefficients between P5N and ALAD, log PROTO, log ALA, and log COPRO were 0.59, -0.72, -0.65, and -0.61, respectively. On the other hand, the normal value of P5N obtained from 72 healthy subjects was 11.9 +/- 2.1 units; mumol uridine/h/g Hb (mean +/- SD), indicating that the lower limit of 95% confidence interval for normal P5N was about 8 units. When P5N was cut off at less than or equal to 8 units in 77 lead workers, the validity (sensitivity + specificity) for PbB greater than or equal to 40 micrograms/dl, PbB greater than or equal to 60 micrograms/dl, erythrocyte PROTO greater than or equal to 150 micrograms/dl RBC, urinary ALA greater than or equal to 6 mg/l, and urinary COPRO greater than or equal to 150 micrograms/l was 1.66, 1.76, 1.57, 1.68, and 1.60, respectively. From these results, it was confirmed that the erythrocyte P5N test is suitable for the biological monitoring of exposure to lead in a wide range, and its activity is useful in predicting the disturbance of porphyrin metabolism induced by lead.

Species difference of urinary excretion of delta-aminolevulinic acid and coproporphyrin in mice and rats exposed to lead

The urinary excretion of delta-aminolevulinic acid (ALA) was first investigated in mice exposed to lead in the drinking water (500 ppm) for 30 days, and the results were compared with those obtained from rats exposed to lead under the same exposure condition. The result indicated that the level of urinary ALA excretion in lead-exposed mice was much higher than that in lead-exposed rats. This finding suggests a species difference between mice and rats with regard to sensitivity to lead. On the other hand, urinary coproporphyrin (CP) was also determined in rats and mice exposed to lead. The result obtained indicated that the increasing level of urinary CP excretion was higher in rats than in mice, contrary to expectation. The reason for the discrepancy between urinary excretion of ALA and that of CP in rats and mice exposed to lead is, however, unknown.

Comparison of inhibition of erythrocyte pyrimidine 5'-nucleotidase and delta-aminolevulinic acid dehydratase by lead

The effect of lead on the activities of erythrocyte pyrimidine 5'-nucleotidase (P5N) and delta-aminolevulinic acid dehydratase (ALAD) was investigated in control and lead-exposed workers. The inhibitory effect of lead in vivo and in vitro was more remarkable on the ALAD than on the P5N activity values. It was demonstrated that the pH optimum of both ALAD and P5N in lead workers shifts to the acidic side (nearly pH 6.0) compared to that in control workers.

Urinary excretion of 5-hydroxyindoleacetic acid, delta-aminolevulinic acid and coproporphyrin isomers in rats and men exposed to lead

The urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA), delta-aminolevulinic acid (ALA) and coproporphyrin (CP) isomers (I and III) was investigated in rats and workers exposed to lead. Urinary excretion of 5-HIAA, which is the major metabolite of serotonin, was not influenced by the lead exposure. However, a significant increase in urinary ALA and CP was found in rats and workers exposed to lead. In particular, the urinary excretion of CP-III was markedly increased compared to that of CP-I in rats and workers exposed to lead.

Optimized liquid-chromatographic method for fluorometric determination of urinary delta-aminolevulinic acid in workers exposed to lead

We developed a fluorometric method for determining delta-aminolevulinic acid (ALA) in urine of lead workers. A high-performance liquid chromatograph (HPLC) equipped with a fluorescence HPLC monitor is used. The detection limit for aqueous ALA is 20 micrograms/L (15 pmol of ALA in the 100-microL sample). The working linear range of urinary ALA concentration was 0.1 to 100 mg/L. In 25 lead-exposed workers, ALA values by the present method for urine correlated well with those obtained by a conventional colorimetric method (r = 0.996). The advantage of the present method for micro-determination of urinary ALA is its high sensitivity.

Optimized liquid-chromatographic method for fluorometric determination of urinary delta-aminolevulinic acid in workers exposed to lead

We developed a fluorometric method for determining delta-aminolevulinic acid (ALA) in urine of lead workers. A high-performance liquid chromatograph (HPLC) equipped with a fluorescence HPLC monitor is used. The detection limit for aqueous ALA is 20 micrograms/L (15 pmol of ALA in the 100-microL sample). The working linear range of urinary ALA concentration was 0.1 to 100 mg/L. In 25 lead-exposed workers, ALA values by the present method for urine correlated well with those obtained by a conventional colorimetric method (r = 0.996). The advantage of the present method for micro-determination of urinary ALA is its high sensitivity.

Simple liquid-chromatographic determination of urinary coproporphyrin in workers exposed to lead

We developed a simple method for the determination of urinary coproporphyrin (CP) in lead workers, using a "high-performance" liquid chromatograph (HPLC) equipped with a fluorescence detector. The detection limit of urinary CP in this method was 5 micrograms per liter of urine. The working linear range of urinary CP concentration was 5 to 1500 micrograms/L. In 41 lead-exposed workers, the urinary CP values obtained by the present HPLC method were well correlated with those obtained by a conventional spectrophotometric method (r = 0.94). The present method is useful for screening workers exposed to lead.