Dose-dependent suppression of toluene metabolism by isopropyl alcohol and methyl ethyl ketone after experimental exposure of rats

In order to examine possible suppression of toluene metabolism due to coexposure to other solvents, female Wistar rats were exposed for 8 h to toluene alone (at 50 or 100 ppm), or in combination with either methyl ethyl ketone (at 50, 100, 200 or 400 ppm) or isopropyl alcohol (at 50, 100, 200, 400, 800 or 1600 ppm). Urine samples were collected for 24 h after initiation of each exposure, and subjected to analysis for two toluene metabolites, hippuric acid and o-cresol, both by HPLC. The excretion of hippuric acid, a major metabolite, was not modified when the concentrations of methyl ethyl ketone or isopropyl alcohol were low, i.e. 100 ppm or below, whereas it was reduced when methyl ethyl ketone or isopropyl alcohol concentrations were twice or more times higher than that of toluene. There were no changes in any cases in excretion of o-cresol, a minor metabolite. The observation after coexposure to methyl ethyl ketone or isopropyl alcohol at low concentration is in line with the negative interaction between toluene and methyl ethyl ketone as well as between toluene and isopropyl alcohol after occupational exposures at low concentrations. Metabolic interaction may take place when the exposure intensity is high, as observed in the present study and also after experimental exposure of volunteers to toluene and m-xylene, or occupational exposure to benzene and toluene.     

Brain stem evoked potentials and visual evoked potentials in relation to the length of occupational exposure to low levels of toluene

In 49 printing-press workers occupationally exposed to toluene for approximately 21.6 years, the values of BEAP and VEP parameters were examined in relation to the length of exposure. With the exception of P2 wave, there was a significant increase in the latencies of all the BEAP waves examined as well as in the interpeak latency (IPL) P3-P4, whereas IPL P4-P5 decreased significantly with the length of exposure. The amplitude of all the VEP examined decreased significantly with the length of exposure. Toluene exposure was evaluated by measuring the concentration of toluene in peripheral blood and of hippuric acid in urine on Wednesday morning prior to the workshift, and of hippuric acid in urine after the workshift on the same day. According to the average concentration of hippuric acid in urine after the workshift, the levels of toluene exposure were estimated to range from 40-60 ppm. Evoked potentials were determined on Mondays 10-12 hours after a nonworking weekend.     

MST-16, a novel derivative of bis(2,6-dioxopiperazine), synergistically enhances the antitumor effects of anthracyclines

OBJECTIVE: The aim of this study was to evaluate whether toluene, like many other organic solvents and solvent mixtures, could impair color vision. SUBJECTS AND METHODS: We investigated color vision impairment in three groups of workers, two groups occupationally exposed to toluene and a nonexposed group. The first exposed group, group E1, comprised 41 workers (median value of toluene in air 35.00 ppm, range 11.3-49.3 ppm) and the second exposed group, group E2, comprised 32 subjects (median value of toluene in air 156.00 ppm, range 66.0-250.0 ppm). The nonexposed group, group NE, comprised 83 subjects. Color vision was evaluated by the Lanthony D-15 desaturated test according to Verriest's classification: type I, loss in the red-green range; type II, loss in the blue-yellow and red-green ranges, and type III, loss in the blue-yellow range. Subjects were classified as dyschromates if specific acquired loss was determined in at least one eye. In both exposed groups, exposure was evaluated by measurement of the concentration of toluene in the ambient air and in the blood. In group E2, level of hippuric acid and orthocresol in urine after the work shift were also determined. The Mann-Whitney U-test, t-test, chi 2-test, and Spearman's rank correlation and multiple regression analysis were used for statistical analysis. RESULTS: Type III dyschromatopsia was detected in all groups examined: 26.6% of the workers in group NE, 31.7% of those in group E1, and 50% of those in group E2. As many as 15.6% of the workers in group E2, 4.8% of those in group E1, and only 1.2% of those in group NE had type II dyschromatopsia. A statistically significant difference in the prevalence of total dyschromatopsia (type III + type II) was established among the three examined groups together (chi 2 = 14.13; df = 2; P < 0.01), between group E2 and group E1 (chi 2 = 4.96; P < 0.05), and between group E2 and group NE (chi 2 = 12.50; P < 0.005), whereas no significant difference was found between groups E1 and NE. Type III dyschromatopsia was significantly correlated with age in group NE (P < 0.01) and in group E1 (P < 0.005). In group E2, both type II (P < 0.05) and type III dyschromatopsia correlated with toluene in ambient air and with the duration of exposure to toluene (both P < 0.005). In group E2, total dyschromatopsia correlated significantly with toluene in ambient air and in blood (both P < 0.05) as well as with hippuric acid in urine after the work shift (P < 0.001). CONCLUSION: This study suggests that toluene can impair color vision.     

Quantitative determination of hippuric acid in urine using high pressure liquid chromatography (author's transl)]

A simple method to determine hippuric acid in urine by high pressure liquid chromatography is described. An ion exchange column is used for the separation. The detection is carried out with a photometer. The analytical criteria of the reliability of the method are tested. The results for the precision and the accuracy of the method meet the guidelines of the statistical quality control. 34 urinary constituents were tested for their interference in order to examine the specificity. Measuring urine samples from 46 normal persons yielded hippuric acid concentrations between 160 and 2010 mg/1. The median was 400 mg/1, equivalent to 357 mg/g creatinine. These results are compared to those given in the literature. Comparative investigations of those urine samples by a gas chromatographic method matched well, with a coefficient of regression of 0.86.     

Distribution and role of aspartate in the nervous system of the chaetognath Sagitta

Forty-nine female workers in the shoemaking industry, exposed to a solvent mixture containing benzene and twenty-seven non-exposed controls, were investigated. Concentrations of benzene and toluene in the working atmosphere, as well as benzene and toluene in blood and phenols in pre- and post-shift urine as parameters of biological monitoring, were determined. In order to assess hematotoxic risk, a complete blood cell count with differential, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, reticulocytes, serum iron, alkaline phosphatase in neutrophils and red blood cell glycerol lysis time were determined in all subjects. Benzene concentrations in the workplace atmosphere at the shoemaking factory ranged from 1.9 to 14.8 ppm (median = 5.9). Significant difference in benzene in blood (p = 0.005) and phenol in post-shift urine (p = 0.003) between exposed workers and controls confirmed exposure to benzene. Hemoglobin level (p = 0.02) and mean corpuscular hemoglobin concentration (p = 0.0002) in the shoe workers were lower, and band neutrophils (p = 0.005) and mean corpuscular volume (p = 0.03) higher, than in controls. Red blood cell glycerol lysis time was significantly higher (p = 0.000001) in shoe workers (X +/- SD = 41.6 +/- 8.9) than in controls (X +/- SD = 31.1 +/- 6.5) and showed a significant correlation with exposure biomarkers. The results confirm that benzene exposure below 15 ppm may produce qualitative abnormalities, particularly macroerythrocytosis and increased red cell glycerol resistance, in the absence of an overt quantitative decrease in circulating blood cells. Increased resistance to the hemolytic action of glycerol is a potentially useful biological monitoring procedure in medical surveillance of benzene exposed workers. The results of this study suggest that potential threshold concentration for hematologic effects of benzene is lower than 15 ppm.     

Rat fetal ventral mesencephalon grown as solid tissue cultures: influence of culture time and BDNF treatment on dopamine neuron survival and function

The method of analysis described permits the determination of 2,4-dinitrobenzoic acid down to the lower microg l(-1) range in the urine of persons exposed to dinitrotoluene. 2,4-Dinitrobenzoic acid is the main metabolite of 2,4-dinitrotoluene and technical dinitrotoluene. After acidic hydrolysis, which served to release the conjugated part of the 2,4-dinitrobenzoic acid, the analyte was selectively separated from the urine matrix via various extraction steps and then derivatised to the methyl ester. Quantitative analysis was carried out using capillary gas chromatography and mass selective detection. 3,5-Dinitrobenzoic acid was used as an internal standard. The detection limit was 1 microg l(-1) urine. The relative standard deviations of within-series imprecision were between 5 and 6%. The relative recoveries were between 91 and 110% depending on the concentration. The analytical method developed as part of this study was used to investigate a collective consisting of 82 urine samples from persons working in the area of explosives disposal. The concentrations of 2,4-dinitrobenzoic acid determined ranged from the detection limit to 95 microg l(-1) urine. The method allowed the quantification of low-level internal exposure to dinitrotoluene.     

Exposure to methyl tertiary-butyl ether from oxygenated gasoline in Stamford, Connecticut

In 1993, state health officials in Connecticut invited the Centers for Disease Control and Prevention (CDC) to assist in an investigation of exposure to methyl tertiary-butyl ether in oxygenated gasoline in Stamford, Connecticut. Venous blood samples were collected from 14 commuters and from 30 other persons who worked in the vicinity of traffic or automobiles, and the samples were analyzed for methyl tertiary-butyl ether, tertiary-butyl alcohol, benzene, m-/p-xylene, o-xylene, and toluene. The highest levels of methyl tertiary-butyl ether in blood were measured among gasoline service station attendants (median = 15 micrograms/l, range = 7.6-28.9 micrograms/l). Blood levels of methyl tertiary-butyl ether were highly variable among persons who worked in car-repair shops (median = 1.73 micrograms/l, range = 0.17-36.7 micrograms/l) and were generally lowest among commuters (median = 0.11 micrograms/l, range = < 0.05-2.60 micrograms/l). Blood levels of methyl tertiary-butyl ether were correlated strongly with personal-breathing-zone samples of methyl tertiary-butyl ether and blood levels of other volatile organic compounds. This exposure information should prove useful to a future risk analysis of this high-volume chemical.     

Association between the clastogenic effect in peripheral lymphocytes and human exposure to arsenic through drinking water

We describe the association between structural chromosome aberrations (CAs) and parameters of exposure to arsenic among 42 individuals exposed to arsenic through well waters in Finland. The median concentration of arsenic in the wells was 410 microg/l, the total arsenic concentrations in urine (As-tot) was 180 microg/l, and in hair 1.3 microg/g, for current users (n = 32) of contaminated wells. Urinary arsenic species and CAs were also analyzed in eight control individuals from the same village who consumed water which contained arsenic <1.0 microg/l (detection limit). Increased arsenic exposure, indicated best by increased concentrations of arsenic species (inorganic arsenic, methylarsonic acid (MMA), dimethylarsinic acid (DMA)) in urine, was associated with increased frequency of CAs. The increased urinary ratio of MMA/As-tot and the decreased ratio of DMA/As-tot were associated with increased CAs when all aberration types, including gaps, were considered. Associations between CAs and arsenic exposure indicators were stronger among current users than among persons who had stopped using the contaminated well water for 2-4 months before sampling (ex-users, n = 10). Furthermore, there was a positive but not statistically significant association between CAs and arsenic in hair among the current users, but not among the ex-users, who still had relatively high arsenic concentrations in hair. The results suggest that the effect observed in the present study reflects relatively recent arsenic exposure.     

Quantitation of o-, m- and p-cresol and deuterated analogs in human urine by gas chromatography with electron capture detection

A gas chromatographic method for the analysis of cresol metabolites of toluene and [2H8]toluene in urine was developed. Cresol glucuronides and sulfates in urine were hydrolyzed with beta-glucuronidase and arylsulfatase. Following extraction with tert.-butyl methyl ether and solvent exchange into benzene, the cresols were derivatized with heptafluorobutyric anhydride to form the heptafluorobutyrate esters. The derivatives were analyzed by gas chromatography with electron capture detection. Chromatographic resolution was achieved between all cresol isomers and their 2H7 analogs. Calibration ranged from 0.001 to 500 microg/ml. Recoveries were 55-97% and showed no trend with respect to analyte concentration. Within-day precision of analyses of benchmark urine samples had a coefficient of variation of less than 4%. The assay sensitivity was limited by chromatographic background but was sufficient for quantification of the unlabeled cresols in urine from men with only environmental exposure to toluene. Average levels in urine samples from 45 men were 0.023, 0.054 and 37 microg/ml for o-, m- and p-cresol, respectively.     

Internal hazardous substance burden of persons from various regions of origin--studies of lead, mercury, arsenic and cadmium exposure

AIM OF THE STUDY: The aim of this study was to investigate the concentration of metals of environmental-medical relevance in biological materials in persons seeking asylum with regard to their country of origin. COLLECTIVE AND METHOD: During medical examination after entry into Germany of persons seeking asylum, samples were taken for determination of the following biological monitoring parameters: lead in blood, and arsenic, cadmium and mercury in urine. A total of 103 males were investigated (13 from former Yugoslavia, 29 from the former USSR, 33 Africans and 28 Asians) ranging from 16 to 53 years of age (median 27 years). 34 male Germans without occupational exposure to these substances and a similar age structure (age 25-36 years; median 26 years) served as a control group. RESULTS: The countries of origin had a significant influence on all the biological monitoring parameters investigated. The mean blood lead concentration in the Asians of 75.4 micrograms/L was the highest level found, while the lowest concentration of 38.0 micrograms/L was measured in the German controls. Also the level of arsenic excreted in the urine was on average much higher in the persons seeking asylum than in the German controls. In the Africans a mean level of 9.7 micrograms/g creatinine was reached. The Germans had the lowest arsenic concentrations in urine of 5.3 micrograms/g creatinine. There were, however, considerable interindividual fluctuations, which are probably due to oral uptake of arsenic compounds as a result of eating seafoods. The highest mean concentration of mercury excreted in urine was found in the German controls. Values of 0.9 microgram/g creatinine were determined. The men seeking asylum from former Yugoslavia had significantly higher values than other groups for cadmium excreted in urine. The median of 0.6 microgram/g creatinine was nearly three times as high as found in the Germans. CONCLUSIONS: For all parameters investigated, with the exception of mercury, higher internal exposure was found in the persons seeking asylum than in the German controls. This may be due to individual life style, dietary habits or environmental conditions in the country of origin. For clinical environmental medicine, the 95th percentile, as the upper limit of the reference range, can only be regarded as an orientation aid for classifying the exposure to hazardous substances of an individual compared to other persons from the same environment.     

Changes in autonomic function as determined by ECG R-R interval variability in sandal, shoe and leather workers exposed to n-hexane, xylene and toluene

To clarify if autonomic nervous system effects might be associated with exposure to organic solvents, 30 sandal, shoe and leather workers exposed to n-hexane, xylene, and toluene, and 25 unexposed controls were examined using the coefficient of variation in electrocardiographic R-R intervals (CVRR), combined with the distribution of nerve conduction velocities (DCV). The C-CVRSA and C-CVMWSA (two component CVs of the CVRR reflecting parasympathetic and sympathetic activities, respectively) were also computed from component spectral powers using autoregressive spectral and component analyses. Concentrations of the metabolites of the solvents in urine samples taken in the morning before work were 0-3.18 (mean 1.39) mg/l for 2,5-hexanedione, 0.10-0.43 (mean 0.19) g/g creatinine (Cn) for methylhippuric acid, and 0.05-2.53 (mean 0.41) g/g Cn for hippuric acid. In the solvent workers, the CVRR and C-CVRSA were reduced significantly when compared with the unexposed controls. The faster velocities of the DCV as well as the sensory median nerve conduction velocity (SCV) were significantly slowed in the solvent-exposed workers. The SCV was significantly correlated with the CVRR and C-CVMWSA among the solvent workers. These data suggest that chronic exposure to some organic solvents may affect cardiac autonomic function (mainly, parasympathetic activity) in addition to faster myelinated fibers of the peripheral nerves. However, the absence of significant dose-effect relations among the solvent workers makes it difficult to definitively attribute the differences to specific solvent exposures.     

Urinary excretion of phenols as an indicator of occupational exposure in the coke-plant industry

OBJECTIVE: In the present study the relationship between the level of exposure to o-cresol and of 2,4- +2,5-, 3,4-, and 3,5-xylenols and the urinary excretion of their metabolites was examined. The mixed exposure to phenolic derivatives of exposed workers during their work shift was monitored by personal air sampling of the breathing-zone air and by measurements of phenol, o-cresol, and xylenol isomer concentrations in shift-end urine. METHODS: The study subjects were 76 men working at a coke plant who were 22-58 years old and 34 nonexposed subjects. Concentrations of phenolic compounds were determined in the breathing-zone air during the work shift, whereas concentrations of phenol, cresol, and xylenol isomers were measured in urine collected after the work shift. Concentrations of phenols in air and urine were determined by gas chromatography with flame-ionization detection. Urine samples were extracted after acid hydrolysis of glucuronides and sulfates by solid-phase extraction. The gas chromatography-mass spectrometry method was applied to identify metabolites in urine samples. RESULTS: The time-weighted average concentrations of phenol, cresol, and xylenol isomers detected in breathing-zone air showed that the exposure level of the workers was relatively low. The geometric mean values were as follows: 0.26 mg/m3 for phenol, 0.09 mg/m3 for o-cresol, 0.13 mg/m3 for p- and m-cresol, and 0.02-0.04 mg/m3 for xylenols at the tar-distillation process. Corresponding urinary concentrations were 10.39, 0.53, and 0.25-0.88 mg/g creatinine for phenol, o-cresol, and xylenol isomers, respectively. The correlation coefficients between the o-cresol and 2,4-, 2,5-, 3,4-, and 3,5-xylenol concentrations measured in urine and in the breathing-zone air were statistically significant, varying in the range of 0.54-0.74 for xylenol isomers and being 0.69 for o-cresol. CONCLUSION: We have found that the presence of o-cresol and xylenol isomers in urine can be used as a biomarker for phenol exposure. Analysis performed on workers at the tar-distillation process showed that they were exposed to relatively low concentrations of phenolic compounds.     

Inhalation toxicokinetics of butoxyethanol and its metabolite butoxyacetic acid in the male Sprague-Dawley rat

A total of 16 male Sprague-Dawley rats were continuously exposed to 20 ppm or 100 ppm butoxyethanol (BE) vapor for 1, 2, 3, 4, 6, 8, 10, or 12 days. Urine was collected in 24-h intervals and stored at -70 degrees C. At the end of the exposure the animals were euthanized by decapitation and tissue samples of blood, muscle, liver and were rapidly collected and frozen to -70 degrees C. The samples were later derivatized and analyzed for BE and its major metabolite butoxyacetic acid (BAA) by electron capture gas chromatography. BE and BAA were rapidly distributed to the tissues examined. The concentration of BE in blood was slightly higher, and that of BAA markedly higher than in other tissues, indicating weak (BE) and pronounced (BAA) blood protein binding, respectively. BE was efficiently metabolized and the blood clearance averaged 2.6 l/h per kg, corresponding to a hepatic extraction ratio of about 0.75. The renal clearance of BAA (average 0.53 l/h per kg) corresponded to approximately 15% of the renal blood flow. The kinetics of BE and BAA were linear up to 100 ppm. There were no clear indications of changes in the toxicokinetics, such as metabolic induction or inhibition of metabolism or excretion, during the course of the exposure. The recovery of BAA in urine was 64% of the calculated inhaled amount of BE, on an equimolar basis.     

Dietary sources and background levels of hippuric acid in urine: comparison of Philippine and Japanese levels

Levels of sodium benzoate in processed food from the Philippines and Japan were analyzed by high performance liquid chromatography. Results showed that of the 44 samples from the Philippines, 31 (70%) contained the compound. The samples with sodium benzoate included 19 juice, 6 softdrink and 6 soy sauce varieties. As for the Japanese products, only 8 (26%) out of 31 food items tested positive for sodium benzoate. The values of the compound in the Philippine samples ranged from 20 micrograms/ml to more than 2,000 micrograms/ml; the Japanese products showed a range of 50 to 200 micrograms/ml. Background urinary hippuric acid levels in 43 male Filipinos and 34 male Japanese with no occupational exposure to toluene were also measured using a high performance liquid chromatograph. Hippuric acid levels expressed as geometric means (SD) were 0.11 g/g creatinine (0.41) for the Filipino subjects and 0.09 g/g creatinine (0.39) for the Japanese subjects. No statistically significant difference in hippuric acid values in the 2 groups was noted. Possible explanations for the lack of any difference in background urinary hippuric acid levels between Filipino and Japanese subjects were discussed.     

Medical surveillance studies of workers exposed to low level benzene

The paper presents th results of an investigation of haematotoxicity in workers exposed to low benzene concentrations. Forty-seven female workers in the shoemaking industry, exposed to solvent mixture and twenty-seven non-exposed controls were examined. Benzene concentrations in the working atmosphere ranged from 1.9 to 14.8 ppm. Significant differences in the levels of benzene in blood and phenols in pre- and post-shift urine between the exposed and control groups confirmed benzene exposure. Haemoglobin level and mean corpuscular haemoglobin concentration were significantly lower, and mean corpuscular volume was higher in the shoemaking workers than in controls. In the subgroup of shoemaking workers exposed to benzene concentrations of 5 ppm or lower, no differences in haematological parameters were found. In conclusion, exposure to a benzene concentration lower than 5 ppm does not appear to produce an increased level of abnormal haematological outcomes detectable in routine medical surveillance. The results of the study corroborate the present maximum permissible concentrations (5 ppm) as a protective limit preventing the onset of haematotoxic non-leukemogenic effects of chronic benzene exposure.     

Clinical observations of unresponsive mucosal leishmaniasis

Ten patients received 2000 mg of ceftazidime intravenously before undergoing lower-extremity amputation for ischaemia. Bone and plasma concentrations were determined by HPLC. The bone concentrations were corrected for blood contamination. In all but one sample ceftazidime was detectable. The median concentration in the midfoot, 4.8 microg/g (range 1.2-11.4 microg/g), was higher than the median concentration in the forefoot, 3.1 microg/g (range 0.8-15.7 microg/g) (P <0.05). In the majority (>90%) of bone samples taken from sites with gangrenous skin the ceftazidime concentration was >1.8 mg/kg bone. The present data indicate that ceftazidime penetrates into bone of severely ischaemic limbs.     

Refined genetic localization of the Best disease gene in 11q13 and physical mapping of linked markers on radiation hybrids

In the framework of the system of monitoring the environmental impact on population health, the concentration of lead, cadmium and selenium in blood and cadmium in urine was measured in adults (n = 670), children (n = 599) and umbilical blood (n = 549) using atomic absorption spectrophotometry. Furthermore, cytogenetic analysis of peripheral lymphocytes in all population groups under study was investigated. The median blood Pb level for the overall group of adults (47.8 micrograms/l, i.e. 0.23 mumol/1) was significantly higher in men (51.5 micrograms/l, i.e. 0.25 mumol/l). Smoking significantly influenced the blood Pb level in women. The 90th percentile in no group exceeded the value of 100 micrograms/l (0.48 mumol/l). The median blood Cd level in adults (0.9 microgram/l, i.e. 0.008 mumol/l) depends on smoking habit (1.25 micrograms/l, i.e. 0.01 mumol/l). The median urine Cd level was 0.585 microgram/g creatinine (0.59 mumol/mole creatinine) in adults and 0.37 microgram/g creatinine (0.37 mumol/mole creatinine) in children. The median blood Se level (53.5 micrograms/l, i.e. 0.68 mumol/l) was found to be higher in the group of non-smokers (57.5 micrograms/l, i.e 0.73 mumol/l). Lead and selenium level were significantly lower in the umbilical blood. Cytogenetic analysis results showed age-dependent average percentages of aberrant cells: 1.1% in umbilical blood, 1.27% in children and 1.71 in adults in line with the reference values for the Czech population.     

Assessment of lead exposure in schoolchildren from Jakarta

Children attending schools in urban areas with high traffic density are a high risk group for lead poisoning. We assessed the magnitude of lead exposure in schoolchildren from Jakarta by analyzing blood lead concentrations and biomarkers of heme biosynthesis. A total of 131 children from four public elementary schools in Jakarta (two in the southern district and two in the central district) were enrolled in the study. To evaluate lead pollution in each area, soil samples and tap water were collected. The mean blood lead concentration was higher in the central district than in the southern district (8.3 +/- 2.8 vs. 6.9 +/- 3.5 microg/100 ml; p<0.05); 26.7% of the children had lead levels greater than 10 microg/100 ml. In 24% of the children, zinc protoporphyrin concentrations were over 70 micromol/mol hemoglobin; in 17% of the samples, hemoglobin was less than 11 g/100 ml. All other values were within the physiological range. Blood lead concentration and hematological biomarkers were not correlated. Analyses of tap water revealed lead values under 0. 01 mg/l; lead contamination of soil ranged from 77 to 223 ppm. Our data indicate that Indonesian children living in urban areas are at increased risk for blood lead levels above the actual acceptable limit. Activities to reduce pollution (e.g., reduction of lead in gasoline) and continuous monitoring of lead exposure are strongly recommended.     

Distribution of a stable isotope of chromium (53Cr) in serum, urine, and breast milk in lactating women

To determine the fate and distribution of chromium during lactation, six lactating women (25-38 y old) were given three doses of the tracer 53Cr (7.55 micromol/d, or 400 microg/d) on days 1, 2, and 3 of the study. Diet records, blood samples taken while subjects were fasting, and 24-h composite milk and urine samples were collected from day 0 to day 6. Fasting blood samples, morning milk samples, and 24-h urine samples were also collected on days 8, 10, 15, 30, 60, and 90. 53Cr and natural and total chromium concentrations in biological fluids were measured with gas chromatography-mass spectrometry and total urinary chromium was measured with atomic-absorption spectrometry. 53Cr was detectable in serum 2 h after dosing and continued to be detected from day 30 to day 60. Changes in total serum chromium concentration in response to the oral dose suggested that chromium concentrations in blood were not tightly regulated. 53Cr was not detected in breast milk and no significant changes in natural chromium concentration in milk were observed in response to the oral doses, suggesting that breast-milk chromium concentrations are independent of intake. The estimated chromium intake of exclusively breast-fed infants was 2.5 nmol/d (0.13 microg/d), below the lower end of the range of estimated safe and adequate daily dietary intakes (10-40 microg/d) for infants 0-6 mo of age. The baseline chromium concentration in urine and the minimum 53Cr absorption in lactating women were comparable with values for nonpregnant, nonlactating subjects. Chromium losses in breast milk do not appear to be compensated for via increased absorption or decreased excretion.     

Evaluation of liver function by co-administration methodology using 13C-labelled benzoic acid and hippuric acid coupled with nuclear magnetic resonance spectroscopy

The amount of hippuric acid synthesized and excreted in the urine after benzoic acid loading (hippuric acid test) is a useful index of liver function. However, the hippuric acid test gives erroneous results in the event of failure of renal excretory function. A new stable isotope co-administration methodology using nuclear magnetic resonance (NMR) spectroscopy has been developed to overcome this defect. [7-(13)C]Benzoic acid and [glycine carbonyl-13C]hippuric acid ([gly-13C]hippuric acid), each 0.4-0.6 mmol kg(-1) were simultaneously administered intravenously as probes to normal or liver-injured rats and the urine was analysed by 100 MHz 13C NMR spectroscopy. Consequently, urinary excretion of [7-(13)C]hippuric acid formed from [7-(13)C]benzoic acid and [gly-13C]hippuric acid was successfully traced with very simple and convenient procedures. The urinary excretion of [7-(13)C]hippuric acid indicated the combined functions of hippuric acid synthesis and renal excretion, whereas that of [gly-13C]hippuric acid was indicative of renal excretion of hippuric acid only. The heights of resonances for C7 of [7-(13)C]hippuric acid and the glycine carbonyl carbon of [gly-13C]hippuric acid were used to calculate the concentrations of labelled hippuric acids. [7-(13)C]Hippuric acid was excreted more slowly than [gly-13C]hippuric acid by both normal and liver-injured rats. The liver-injured rats excreted the labelled hippuric acids more slowly than the normal rats. The kinetic parameters were computed for the individual rats on the basis of Michaelis-Menten elimination for benzoic acid and first-order elimination for hippuric acid. The maximum rates of metabolism (Vmax) (4.8-5.8 micromol min(-1) kg(-1)) and the renal elimination rate constants of hippuric acid (Kre) (0.010-0.021 min(-1)) in the liver-injured rats were lower than those (Vmax 6.7-11.8 micromol min(-1) kg(-1); Kre 0.026-0.045 min(-1)) in the normal rats. These results have demonstrated that liver function can be evaluated from the Vmax value even though the renal function of hippuric acid excretion (Kre) is impaired. Thus the co-administration methodology is feasible and can remove the defect of the previous hippuric acid test. These results could form the basis for a more convenient and reliable hippuric acid test in man.