Erythrocyte arginase, pyrimidine 5''-nucleotidase (P5N), and deoxypyrimidine 5''-nucleotidase (dP5N) as indices of lead exposure.

The activities of three erythrocyte (rbc) enzymes, arginase, pyrimidine 5'-nucleotidase (P5N), and deoxypyrimidine 5'-nucleotidase (dP5N), were compared in 16 lead workers and 14 age matched controls as correlates of blood lead (PbB) and unextracted zinc protoporphyrin (EP) concentrations. Subjects with PbB of 0.9-2.5 microM (19-52 micrograms/dl) had 6.5 +/- 0.6 IU of P5N activity with uridine monophosphate (UMP) as substrate, significantly less (p less than 0.001) than the 12.0 +/- 0.7 IU activity of controls with PbB 0.3-0.6 microM (6-12 micrograms/dl). The mean activity of rbc dP5N with either deoxyuridine monophosphate (dUMP) or thymidine monophosphate as substrate, and of rbc arginase, did not differentiate the two groups. The correlation coefficients of ln PbB with the selected substrates for P5N and dP5N were: UMP, r = -0.75; dUMP, r = -0.61; TMP, r = -0.23. The correlation coefficient of ln PbB and arginase activity was -0.03. Rbc P5N (UMPase) is a significant correlate of PbB, equivalent to rbc protoporphyrin. HPLC assay of rbc UMPase activity is a sensitive and rapid assay that appears to meet criteria for a reliable clinical laboratory index of blood lead concentrations.     

Determination of pyrimidine 5'-nucleotidase (P5N) activity in whole blood as an index of lead exposure

A simple method for determining pyrimidine 5'-nucleotidase (P5N) activity in whole blood has been developed, inhibiting the plasma activity for UMP-hydrolysis by concanavalin (Con A). Con A specifically inhibits the activity of plasma 5'-nucleotidase (5N) but does not affect erythrocyte P5N activity. The anticoagulant EDTA partially inhibits 5N activity but slightly activates P5N. P5N activity determined by the present method with heparinised blood and Con A was comparable with that by the method reported previously and correlated well with blood lead concentrations. The mean value and SD for P5N activity in normal subjects (n = 72) not exposed to lead are 16.2 and 2.5 mumole/h/g Hb, respectively. The present method can eliminate not only the isolation step of RBC but also Hb determination, the activity being expressed as mumole/h/l blood or RBC. Thus the procedures are so simplified that the assay may be used as a routine test for mass screening of lead exposure.     

A simplified method for determining erythrocyte pyrimidine 5'-nucleotidase (P5N) activity by HPLC and its value in monitoring lead exposure

The method for determining erythrocyte pyrimidine 5'-nucleotidase (P5N EC 3.1.3.5) activity has been simplified using an automated high performance liquid chromatograph (HPLC). The activity determined by the simplified method agreed closely with that obtained by conventional methods. In 161 lead workers P5N activity declined linearly with increasing blood lead concentrations (Pb-B) between 20 and 80 micrograms/100 g, and correlated well with Pb-B (r = -0.87). For the same group of workers, correlation coefficients between Pb-B v ALA-D activity, zinc protoporphyrin, ALA-U, and coproporphyrin were -0.87, 0.73, 0.70, and 0.32, respectively. At Pb-B greater than or equal to 40 micrograms/100 g, the validity of P5N (1.86 at a cut off of 10 less than or equal to units) was higher than that of other indicators examined. P5N activity was fairly stable during the storage of samples for two weeks at 4 degrees C. Determination of P5N activity by this method may be a useful indicator in screening for moderate exposure to lead.     

Erythrocyte arginase activity as an indicator of lead exposure

ABSTRACT A semi-automated method has been developed for the determination of the arginase activity of erythrocytes using dried blood spots, which are easy to prepare on site in a factory for later laboratory analysis. The mean arginase activity of erythrocytes in 49 men occupationally exposed to lead was 62·9 IU/g·Hb (SD, 14·4 IU/g·Hb); in 45 men not exposed to lead the mean was 44·6 IU/g·Hb (SD, 11·6 IU/g·Hb). A significantly higher mean arginase activity was found in the specimens from lead-exposed workers (p < 0·001). The correlation coefficient between blood lead and erythrocyte arginase was r = 0·67 (p < 0·001). The degree of correlation between blood lead and lead indicators including arginase was r = 0·75 for urine δ-aminolaevulinic acid, r = 0·67 for erythrocyte arginase, r = 0·66 for urine lead, and r = 0·63 for coproporphyrin. Erythrocyte arginase showed no significant correlation in the liver function tests, GOT, GPT, and albumin in serum. When 40 μg/100 g of blood lead concentration was fixed as the basic value and 56·2 IU/g·Hb of erythrocyte arginase activity was set as the screening value in lead-exposed workers, the sensitivity and specificity of the arginase test were 0·96 and 0·65, respectively. Thus the validity of the test was calculated to be 1·61. These results show that the arginase level of erythrocytes can be considered to be one of the significant indicators of occupational exposure to lead because it reflects well the dose-response relationship of lead in the human body. Our method allows rapid analysis of erythrocyte arginase and thus should be useful in screening for lead exposure.     

Determination of pyrimidine 5''-nucleotidase (P5N) activity in whole blood as an index of lead exposure.

A simple method for determining pyrimidine 5'-nucleotidase (P5N) activity in whole blood has been developed, inhibiting the plasma activity for UMP-hydrolysis by concanavalin (Con A). Con A specifically inhibits the activity of plasma 5'-nucleotidase (5N) but does not affect erythrocyte P5N activity. The anticoagulant EDTA partially inhibits 5N activity but slightly activates P5N. P5N activity determined by the present method with heparinised blood and Con A was comparable with that by the method reported previously and correlated well with blood lead concentrations. The mean value and SD for P5N activity in normal subjects (n = 72) not exposed to lead are 16.2 and 2.5 mumole/h/g Hb, respectively. The present method can eliminate not only the isolation step of RBC but also Hb determination, the activity being expressed as mumole/h/l blood or RBC. Thus the procedures are so simplified that the assay may be used as a routine test for mass screening of lead exposure.     

Evaluation of activity of erythrocyte pyrimidine 5'-nucleotidase (P5N) in lead exposed workers: with focus on the effect on hemoglobin

Anemia that accompanies lead poisoning is in part the result of various inhibitory effects of lead on heme biosynthesis. Lead also increases the rate of red blood cell destruction due to the profoundly depressed activities of erythrocyte pyrimidine 5'-nucleotidase (P5N) activities. We studied parameters of the two metabolic pathways in the workers exposed to lead to evaluate P5N in the lead exposed workers and which pathway has an effect on hemoglobin (Hb) level. 29 male workers in the secondary lead smelting as high exposure group, 46 male workers in the manufacturer of inorganic pigment as low exposure group and 56 clerical male workers from another plant as non-exposed group were studied. Activity of P5N, lead concentration in whole blood (PbB), zinc protoporphyrin (ZPP), Hb, and ferritin were determined. In the present study, P5N activity of nucleotide metabolic pathway correlated with Hb after controlling indices of iron deficiency anemia (ferritin) occurring concurrently and heme biosynthetic pathway (ZPP) in the high exposure group while heme biosynthetic pathway did not correlate with Hb after controlling other two variables in exposure groups. These findings suggest that P5N rather than heme biosynthetic pathway has a major effect on Hb level even in workers without manifest hemolytic anemia.     

A simplified method for determining erythrocyte pyrimidine 5''-nucleotidase (P5N) activity by HPLC and its value in monitoring lead exposure.

The method for determining erythrocyte pyrimidine 5'-nucleotidase (P5N EC 3.1.3.5) activity has been simplified using an automated high performance liquid chromatograph (HPLC). The activity determined by the simplified method agreed closely with that obtained by conventional methods. In 161 lead workers P5N activity declined linearly with increasing blood lead concentrations (Pb-B) between 20 and 80 micrograms/100 g, and correlated well with Pb-B (r = -0.87). For the same group of workers, correlation coefficients between Pb-B v ALA-D activity, zinc protoporphyrin, ALA-U, and coproporphyrin were -0.87, 0.73, 0.70, and 0.32, respectively. At Pb-B greater than or equal to 40 micrograms/100 g, the validity of P5N (1.86 at a cut off of 10 less than or equal to units) was higher than that of other indicators examined. P5N activity was fairly stable during the storage of samples for two weeks at 4 degrees C. Determination of P5N activity by this method may be a useful indicator in screening for moderate exposure to lead.     

Evaluation of lead exposure in workers at a lead-acid battery factory in Korea: with focus on activity of erythrocyte pyrimidine 5''-nucleotidase (P5N).

OBJECTIVE--To evaluate lead exposure among lead-acid battery workers in Korea, to evaluate in more detail the erythrocyte pyrimidine 5'-nucleotidase (P5N) test for lead exposure, and to evaluate the abnormal accumulation of erythrocyte pyrimidine nucleotides in the battery workers. METHODS--Activity of P5N and other biological variables were examined in 66 exposed workers in a lead-acid battery factory and in 26 non-exposed workers in Korea. RESULTS--At the factory the time-weighted average of 13 (72%) of 18 air samples for lead exceeded 0.05 (range 0.012-0.468) mg/m3. Blood lead concentration (PbB) in 39 of the 66 exposed workers was above 40 micrograms/dl, and the mean (SD) PbB in the exposed group was 45.7 (15.7) micrograms/dl. Compared with the nonexposed group, free erythrocyte protoporphyrin in the exposed group was significantly increased, whereas erythrocyte P5N activity and activity of erythrocyte delta-aminolevulinic acid dehydratase (ALAD) were significantly inhibited. Erythrocyte P5N activity had valid correlation biologically with PbB and with other biological variables, such as ALAD activity. In 28 exposed workers, the concentration of erythrocyte pyrimidine nucleotides (uridine 5'-diphosphate-glucose and cytidine 5'-triphosphate) correlated inversely with P5N activity and positively with PbB. CONCLUSIONS--These findings show that the depression of erythrocyte P5N activity by lead exposure results in the accumulation of erythrocyte pyrimidine nucleotides. In general, the standard analysis of PbB performed in laboratories around the world remains the most useful index of recent exposure. The results indicate that the erythrocyte P5N activity test provides supporting evidence of lead exposure and shows the effect of lead on nucleotide metabolism.     

Arginase and kallikrein activities as biochemical indices of occupational exposure to lead.

In a group of 60 workers occupationally exposed to lead the blood and urine lead concentrations, haematocrit, ALA-D and arginase activities, and urinary 5-aminolaevulinic acid (ALA) and coproporphyrin concentrations, and kallikrein activity were determined. Correlation coefficients of -0.78 and 0.77 for Pb-B/ALA and Pb-B/arginase were found respectively for lead concentrations above 40 microgram/dl blood, and 0.83, 0.76, 0.74, and -0.64 for Pb-U/ALA, Pb-U/Cp-U, Pb-U/kallikrein, and Pb.U/kallikrein, respectively. It seems that the increase in serum arginase activity may be indicative of liver damage while the decrease in kallikrein activity may indicate kidney damage in workers exposed to lead.     

Activity of erythrocyte delta-aminolevulinic acid dehydrase and its change by heat treatment as indices of lead exposure.

The effect of heat treatment on erythrocyte delta-aminolevulinic acid dehydrase (ALAD) activity in the blood of human subjects was examined in relation to their lead exposure.     

Activity of erythrocyte delta-aminolevulinic acid dehydrase and its change by heat treatment as indices of lead exposure.

The effect of heat treatment on erythrocyte delta-aminolevulinic acid dehydrase (ALAD) activity in the blood of human subjects was examined in relation to their lead exposure.     

Breath, urine, and blood measurements as biological exposure indices of short-term inhalation exposure to methanol

Due to their transient nature, short-term exposures can be difficult to detect and quantify using conventional monitoring techniques. Biological monitoring may be capable of registering such exposures and may also be used to estimate important toxicological parameters. This paper investigates relationships between methanol concentrations in the blood, urine, and breath of volunteers exposed to methanol vapor at 800 ppm for periods of 0.5, 1, 2, and 8 h. The results indicate factors that must be considered for interpretation of the results of biological monitoring. For methanol, concentrations are not proportional to the exposure duration due to metabolic and other elimination processes that occur concurrently with the exposure. First-order clearance models can be used with blood, breath, or urine concentrations to estimate exposures if the time that has elapsed since the exposure and the model parameters are known. The 0.5 to 2-h periods of exposure were used to estimate the half-life of methanol. Blood data gave a half-life of 1.44±0.33 h. Comparable but slightly more variable results were obtained using urine data corrected for voiding time (1.55±0.67 h) and breath data corrected for mucous membrane desorption (1.40±0.38 h). Methanol concentrations in blood lagged some 15–30 min behind the termination of exposure, and concentrations in urine were further delayed. Although breath sampling may be convenient, breath concentrations reflect end-expired or alveolar air only if subjects are in a methanol-free environment for 30 min or more after the exposure. At earlier times, breath concentrations included contributions from airway desorption or diffusion processes. As based on multicompartmental models, the desorption processes have half-lives ranging between 0.6 and 5 min. Preliminary estimates of the mucous membrane reservoir indicate contributions of under 10% for a 0.5-h exposure and smaller effects for longer periods of exposure. Received: 1 August 1996 / Accepted: 24 January 1998     

High performance liquid chromatographic procedure for quantitative determination of urinary delta-aminolevulinic acid as indices of lead exposure

Summary A high performance liquid chromatographic method for the determination of delta-aminolevulinic acids (ALA) in urine, is described. 2-Methyl-3 carbmethoxy-4-(3-propionic acid) pyrrole was produced by the condensation of ALA with methylacetoacetate (MAA) while heating. The methylacetoacetate could be replaced by ethylacetoacetate. The ALA pyrrole thus obtained was injected into high performance liquid chromatography (HPLC). A stainless-steel column packed with octadecyl silanized silica gel was used. The mixed solution of acetonitrile/50mM KH₂PO₄ (adjusted to pH 2.5 with 0.001 volumes of 85 g/dl H₃PO₄)(20/80) was a favorable mobile phase for the separation of ALA. Amino acetone pyrrole was produced by the condensation of amino acetone with methyl acetoacetate. The amino acetone pyrrole appeared later than ALA pyrrole on HPLC. The method is simple and specific. It has a lower detection limit of 0.2 ng on column. The analysis and quantitative determination of one specimen can be performed within 20 min. Mean ALA concentration of normal urine by HPLC was 1.18mg/g creatinine.