Variation In Urinary Excretion Research Articles

#573 Development of a model for simultaneous normothermic perfusion in porcine kidney grafts

Abstract Background and Aims In recent years, DCD or ECD deceased donors have been increasingly used in kidney transplantation as a partial response to the deceased donor shortage, leading to a suboptimal quality of kidney grafts. There is a need for developing better kidney graft preservation methods, such as hypo- or normo- thermic machine perfusion. Machine perfusion might provide the unique opportunity to directly treat the perfused kidney grafts to improve their quality and to decrease ischemia/reperfusion injury during transplantation. Our aim was to develop a pig model of simultaneous normothermic perfusion of both kidneys procured from the same donor and to compare the assessment of renal function through the injection of creatinine and iohexol. Method Under general anaesthesia, the donor pigs (n = 5) were euthanized by exsanguination and the blood was recovered using a cell-saving system. Both kidneys (n = 10) were submitted to 30 min of warm and a 2-hour cold ischemia period, before being perfused for 6 hrs at 37°C. Kidney perfusion started and run in parallel using 2 independents, modified extracorporeal machines. Urine production, arterial blood gas exchange, and perfusion parameters (flow, pressure, resistance) were monitored and compared. Creatinine and iohexol were added to the perfusate of both machines to assess renal function. Results A parallel evolution of blood parameters in both perfusions was observed. By maintaining a constant perfusion pressure of 70 mmHg, flow rates increased to 100 mL/min. Despite variations in urinary excretion, creatinine and iohexol clearances remained comparable, demonstrating a parallel kidney function. Conclusion In conclusion, we established a model of parallel and simultaneous normothermic perfusion of pig kidneys, and for the first time, we demonstrated the utility of iohexol measurements for improved functional assessment in an isolated perfusion model. After randomization of the grafts, this model will be used for testing innovative therapies as MSC during perfusion, both in swine kidneys and human discarded grafts, using the contralateral kidney as a paired control.

Variability and Seasonal Change of Urinary Selenium, Molybdenum, and Iodine Excretion in Healthy Young Japanese Adults.

Selenium (Se), molybdenum (Mo), and iodine (I) are essential trace elements or nutrients and their adequate intake is essential for human health. These elements in foods are easily absorbed from the digestive tract and excreted predominantly into the urine, and their nutritional status is reflected in urinary excretion; however, information on the variability of urinary excretion is limited. To characterize the urinary Se, Mo, and I concentrations and their intra- and inter-individual coefficients of variation (CV), correlation, and seasonal change, spot urine samples were collected from 24 healthy university students, 10 males and 14 females, with the mean age of 20.6years, for 10 consecutive days in each of the four seasons according to a defined schedule of an interval of 3months throughout 1year. The median Se, Mo, and I concentrations for all urine samples (n = 947) were 52.8, 127.0, and 223μg/L, respectively. The Se and Mo intakes were highest in summer and lowest in spring, while the I intake was highest in autumn and lowest in summer. In all three elements, the intra-individual CVs were smaller than their inter-individual CVs. The log-transformed intra- and inter-individual CVs were 10.5 and 14.7% for Se, 12.3 and 15.1% for Mo, and 15.5 and 18.1% for I. There was no gender difference in Se and I concentrations, while Mo and Mo/Cr values in males were higher than those in females. Our results suggest adequate nutritional status of Se, Mo, and I with a relatively smaller variability of dietary intake except for I in this population.

Diurnal variation of magnesium and the mineral metabolism in patients with chronic kidney disease

Increasing levels of magnesium in blood are associated with reduced risk of cardiovascular disease in chronic kidney disease (CKD). Magnesium supplementation may reduce the progression of vascular calcification in CKD. The diurnal pattern and effect of fasting on magnesium in blood and urine in CKD is unknown, and knowledge of this may influence management of magnesium supplementation.We included ten patients with CKD stage four without diabetes mellitus and ten healthy controls. Participants were admitted to our hospital ward for a 24-h study period. Blood and urine samples were collected in a non-fasting state at 8 o'clock in the morning and every third hour hereafter until the final samples in a fasting state at 8 o'clock the following morning.We found no diurnal variation in plasma magnesium (p = 0.097) in either group, but a significant diurnal variation in urinary excretion of magnesium (p = 0.044) in both CKD and healthy controls with no significant interaction between the two groups, and thus no suggestion that CKD affects diurnal variation of plasma magnesium or urinary magnesium excretion. The levels of plasma magnesium were not significantly different in fasting and non-fasting conditions.Magnesium in plasma does not display a significant diurnal variation and can be measured at any time of day and in both fasting and non-fasting conditions. Urinary magnesium excretion displays diurnal variation, which is likely related to increased uptake of magnesium during meals and helps maintain a stable concentration of magnesium in blood.

Comparative evaluation of daily rhythm of urinary excretion in Equus caballus and Bos taurus by means of fractional clearance

ABSTRACTThe aim of this study was to evaluate the daily variations of urinary excretion of the main electrolytes in Equus caballus and Bos taurus maintained under natural photoperiod. Animals were housed in individual indoor stalls under natural conditions. Urine and blood samples were taken from all the subjects every 4 h for 24 h period and were analyzed to assess the creatinine, calcium, phosphorus, magnesium, and chloride concentration. The fractional excretions of Na (%CrNa), K (%CrK), Cl (%CrCl), P (%CrP), Ca (%CrCa), and Mg (%CrMg) were calculated. Daily oscillations with nighttime acrophases of %CrNa, %CrK, and %CrCl are observed in horse; the acrophases of the parameters which resulted periodic in cow, including %CrNa, %CrCa, and %CrMg, are verified during the light phase. This study brings a contribution to the knowledge of the periodic phenomenon of the urinary excretion in the equine and bovine species. The results suggest that horse and cow are characterized by different circadian patterns for renal fractional clearance and that in these species, in addition to the external circadian stimuli, the renal excretion rhythms are also controlled by a self-sustained intrinsic renal clock that contribute to define the temporal patterns (daytime and nighttime).

Inter-individual variability in the production of flavan-3-ol colonic metabolites: preliminary elucidation of urinary metabotypes.

There is much information on the bioavailability of (poly)phenolic compounds following acute intake of various foods. However, there are only limited data on the effects of repeated and combined exposure to specific (poly)phenol food sources and the inter-individual variability in their bioavailability. This study evaluated the combined urinary excretion of (poly)phenols from green tea and coffee following daily consumption by healthy subjects in free-living conditions. The inter-individual variability in the production of phenolic metabolites was also investigated. Eleven participants consumed both tablets of green tea and green coffee bean extracts daily for 8 weeks and 24-h urine was collected on five different occasions. The urinary profile of phenolic metabolites and a set of multivariate statistical tests were used to investigate the putative existence of characteristic metabotypes in the production of flavan-3-ol microbial metabolites. (Poly)phenolic compounds in the green tea and green coffee bean extracts were absorbed and excreted after simultaneous consumption, with green tea resulting in more inter-individual variability in urinary excretion of phenolic metabolites. Three metabotypes in the production of flavan-3-ol microbial metabolites were tentatively defined, characterized by the excretion of different amounts of trihydroxyphenyl-γ-valerolactones, dihydroxyphenyl-γ-valerolactones, and hydroxyphenylpropionic acids. The selective production of microbiota-derived metabolites from flavan-3-ols and the putative existence of characteristic metabotypes in their production represent an important development in the study of the bioavailability of plant bioactives. These observations will contribute to better understand the health effects and individual differences associated with consumption of flavan-3-ols, arguably the main class of flavonoids in the human diet.

Short communication: Individual cow variation in urinary excretion of phosphorus

Some dairy cows excrete large amounts of P through their urine; thus, it was speculated that a genetic defect related to their efficiency in uptake of P or recirculation of P could cause such an effect. This speculation was pursued in a cross sectional study on 139 cows (103 Holstein and 36 Jersey) from an experimental herd using repeated sampling of urine (301 samples) to investigate sources of variation in urinary P concentration (Pu). Urine samples were taken on 6 testing sessions spread over 2 mo. Each sample was obtained by mild manual stimulation of the rear udder escutcheon area. The samples were immediately assayed for pH, stored frozen, and assayed for inorganic P and creatinine. Concentrations of P and creatinine in urine, the ratio of Pu to creatinine, and pH were analyzed using a linear mixed model. The model included fixed effects of breed, parity number, and sampling session. Stage of lactation was fitted as Wilmink-type lactation curves. Random effects included additive polygenic ancestry, permanent animal effects, and residual. The distribution of Pu approximated normality except for a single sample with very high Pu and very low pH. This sample came from a cow diagnosed independently with ketosis. For the remaining samples, it was shown that Pu has low to moderate heritability (0.12) and is only moderately repeatable (0.21). Based on a small data set, it is tentatively concluded that individual differences between cows exist in their Pu, and individual differences presumably result from genetic differences. However, it remains unclear if cows with genetically lower or higher Pu will perform better on a low-P diet.

Altered circadian hemodynamic and renal function in cirrhosis.

Given that alterations in systemic hemodynamics have a profound influence on renal function in patients with cirrhosis, it is surprising that circadian variations in blood pressure (BP) and renal electrolyte excretion have scarcely been studied. Our aims were to define the relationship of 24-h ambulatory BP changes with renal tubular function and to determine the influence of endotoxemia on BP and urinary parameters. Forty healthy controls served as a comparator to 20 cirrhotic patients. They underwent 24-h ambulatory BP monitoring and 24-h urine collection. Subjects with cirrhosis demonstrated significant diurnal variations in urinary excretion of sodium (57.7 µmol/min day versus 87 µmol/min night) and creatinine (826 µg/min day versus 1202 µg/min night). Increasing severity of cirrhosis was associated with a progressive reduction in ambulatory awake systolic (P-trend = 0.015), diastolic (P-trend < 0.001) and mean BP (P-trend < 0.001). In patients with cirrhosis, the magnitude of change in BP from awake to sleep state was blunted for systolic BP (5% reduction, P = 0.039) and pulse rate (2% reduction, P < 0.001). The amplitude of variation in pulse rate was blunted with increasing severity of cirrhosis (controls 6.5, Child-Pugh Class A 5.3, Child B 3.4, Child C 1.2, P = 0.03) and the acrophase was right-shifted with increasing severity of cirrhosis. Compared with sleep state, during the awake state, endotoxin was associated with less sodium excretion and a lower systolic BP. Compared with the awake state, endotoxin was associated with a higher sleeping pulse rate (P < 0.001). Patients with cirrhosis have altered diurnal profiles in renal tubular function and blood pressure that appear to be related to endotoxemia. Determining whether endotoxemia is causally related to these perturbations will require interventional studies.

Quantitative relationships between standardized total tract digestible phosphorus and total calcium intakes and their retention and excretion in growing pigs fed corn-soybean meal diets.

An experiment was conducted to determine the quantitative relationships between standardized total tract digestible P (STTD P) and total Ca intakes with their retention and excretion by growing pigs fed corn-soybean meal diets. Forty-eight crossbred barrows (BW = 22.7 ± 2.9 kg) were allotted to 1 of 8 diets, housed individually in pens for 3 wk, and then moved to metabolism crates and allowed 4 d for adaptation and 5 d for collection of urine and fecal samples. Eight corn-soybean meal diets were formulated for similar NE, fat, and AA concentrations but to increase the STTD P from 0.16 to 0.62% using monocalcium phosphate. Dietary treatments were formulated for a constant Ca:STTD P ratio (2.2:1). The STTD P intake increased (P < 0.001) from 64 to 242% of the daily requirement (4.59 g/d of STTD P). Fecal and total excretion of P and Ca were linearly associated with mineral intake (P < 0.001). Constant urinary P excretion of 0.03 g/d P was observed, but at 4.96 g/d of STTD P intake, the urinary P excretion increased (P < 0.001). In contrast, Ca excretion in urine decreased (P < 0.001) with Ca intake, but constant excretion of 0.40 g/d Ca was reached at 17.97 g/d of Ca intake. The daily intakes of STTD P and Ca moderately explained the variation in urinary excretion of P (R2= 0.41) and Ca (R2= 0.64). The absorption and retention of P increased linearly (P< 0.001) with dietary P intake, whereas absorption and retention of Ca showed a quadratic response (P < 0.001). Absorption and retention of P and Ca were highly predictable from the STTD P and Ca intakes, with of 0.87 and 0.90, respectively. The femur mineral content (FMC) increased by 2.71 g with STTD P intake (P < 0.001) but reached a plateau (29.54 g of FMC) at 8.84 g/d of STTD P intake. The FMC was highly predictable from the STTD P intake (R2 = 0.89). The FMC affected the urinary P excretion ( P< 0.01), but moderately (R2= 0.19) explained the variation in urinary P. In conclusion, constant excretion of P in urine was observed but excretion increased linearly at STTD P intake levels above the requirement for maximum growth of growing pigs. The FMC increased with STTD P intake, but a plateau was reached at a STTD P intake level above the requirement. Dietary STTD P was used for growth and accumulated in bones until a plateau was reached and excess was excreted in urine. The predictability of P and Ca excretion in urine from the dietary STTD P and Ca intakes was moderate.

Inter- and intra-individual variation in urinary biomarker concentrations over a 6-day sampling period. Part 2: Personal care product ingredients

An intensive study was conducted to provide data on intra- and inter-individual variation in urinary excretion of a series of ingredients in personal care products (parabens, triclosan, benzophenones) and bisphenol A (BPA, not expected to be an ingredient) in 8 volunteers over 6 days. Exposure diaries recorded use of personal care products with identified target analytes as ingredients. Participants' usual products were replaced with products without the target analytes for 2 of the 6 days. Urine void volumes and times were recorded. Methyl, ethyl, and n-propylparabens, triclosan, benzophenone-3, and BPA were frequently detected (≥70% of samples). Urinary concentrations of the parabens and triclosan were lower on product replacement days. First morning void concentrations correlated moderately to highly with 24-h composite concentrations for all analytes. Intraclass correlation coefficients (ICCs) for spot samples collected on days with usual product use were low for BPA (0.15), moderate for n-propylparaben and methylparaben (0.39 and 0.56, respectively), and high for ethylparaben, benzophenone-3, and triclosan (0.76, 0.81, and 0.934, respectively); ICCs were consistently higher on the basis of cr-adjusted concentrations. Hydration status adjustment methods were assessed by comparing unadjusted and adjusted concentrations to urinary excretion rates (ER, ng/kg-h) for all analytes and samples. Specific gravity-adjusted concentrations correlated slightly better with ER than creatinine-adjusted concentrations. Within-individual variation in biomarker concentrations was highest for methyl and ethylparabens (2 orders of magnitude variation in spot sample concentrations) and lower for the other analytes (1–1.5 orders of magnitude). This dataset provides insight into the design and interpretation of urinary biomonitoring studies for non-persistent chemicals.

Inter- and intra-individual variation in urinary excretion of daidzein and equol in female Japanese

Objective: To evaluate the representativeness of single measurement of urinary soy-isoflavone concentrations for the assessment of long-term intake levels.Methods: Five urine samples taken from 14 Japanese female subjects over 2–3 months were measured for daidzein and equol by gas chromatography-mass spectrometry (GC-MS).Results: Geometric mean daidzein and equol concentrations of 14 subjects were 582 and 2.66 μg/g creatinine, respectively. Intra-class correlation coefficients for daidzein and equol were 0.355 (95% CI: 0.130–0.649) and 0.741 (0.551–0.891), respectively.Conclusion: Single measurement of urinary equol is effective for the assessment of long-term equol status of Japanese subject while that of daidzein is not.

Temporal variability in urinary excretion of bisphenol A and seven other phenols in spot, morning, and 24-h urine samples

Human exposure to modern non-persistent chemicals is difficult to ascertain in epidemiological studies as exposure patterns and excretion rates may show temporal and diurnal variations. The aim of this study was to assess the temporal variability in repeated measurements of urinary excretion of bisphenol A (BPA) and seven other phenols. All analytes were determined using TurboFlow-LC–MS/MS. Two spot, three first morning and three 24-h urine samples were collected from 33 young Danish men over a three months period. Temporal variability was estimated by means of intraclass correlation coefficients (ICCs). More than 70% of the urine samples had detectable levels of BPA, triclosan (TCS), benzophenone-3 (BP-3) and sum of 2,4-dichlorophenol and 2,5-dichlorophenol (ΣDCP). We found low to moderate ICCs for BPA (0.10–0.42) and ΣDCP (0.39–0.72), whereas the ICCs for BP-3 (0.69–0.80) and TCS (0.55–0.90) were higher. The ICCs were highest for the two spot urine samples, which were collected approximately 4 days apart, compared with the 24-h urine samples and the first morning urine samples, which were collected approximately 40 days apart. A consequence of the considerable variability in urinary excretion of BPA may be misclassification of individual BPA exposure level in epidemiological studies, which may lead to attenuation of the association between BPA and outcomes. Our data do not support that collection of 24-h samples will improve individual exposure assessment for any of the analysed phenols.

Urinary Phthalates From 168 Girls and Boys Measured Twice a Year During a 5-Year Period: Associations With Adrenal Androgen Levels and Puberty

Little is known about the possible deleterious effects of phthalate exposure on endogenous sex steroid levels in children. Our objective was to investigate whether urinary phthalate metabolite levels are associated with circulating adrenal androgen levels and age at puberty. This was a longitudinal study of 168 healthy children (84 girls) examined every 6 months for 5 years. Serum levels of dehydroepiandrostenedione sulfate (DHEAS), Δ4-androstenedione, testosterone, and urinary morning excretion of 14 phthalate metabolites, corresponding to 7 different phthalate diesters were determined. A variation in urinary excretion of phthalates was evident in each child, which made a mean of repetitive samples more representative for long-term excretion than a single determination. We found that girls with excretion of monobutyl phthalate isomers (MBP) and di(2-ethylhexyl) phthalate metabolites above the geometric group mean (795 and 730 ng/kg, respectively) had lower levels of DHEAS and Δ4-androstenedione, although statistically significant only at 13 years of age. In boys, we found that excretion of monobenzyl phthalate above the geometric group mean (346 ng/kg) was associated with lower levels of DHEAS at 11 years of age but higher levels of testosterone at 13 years of age. The same trend was observed for MBP excretion, albeit not statistically significant. A lower age at pubarche was observed in boys with excretion of MBP above the geometric group mean (11.0 vs 12.3 years, P = 0.005). Our data indicate that exposure to dibutyl phthalate isomers (DBP) (in girls) and butylbenzyl phthalate (in boys) are negatively associated with adrenal androgen levels and in boys positively associated with testosterone level at 13 years of age. High exposure to DBP was associated with earlier age at pubarche in boys. In girls, no associations between phthalate exposure and age at pubertal milestones were observed.

Variability of urinary excretion of pyrethroid metabolites in seven persons over seven consecutive days—Implications for observational studies

Concentration of urinary metabolites is frequently used for biomonitoring of exposure to synthetic pyrethroids, the class of non-persistent insecticides. These chemicals are currently widely used in agriculture, households and public health all over the world. Most of them are easily metabolized in mammals and in the form of metabolites excreted in urine. The concentration in urine is thus susceptible to significant variations, even within a short period of time. In this study, temporal changes in urinary metabolites concentrations in seven subjects (four females and three males aged: 24–71) were monitored over seven consecutive days. All urine voids (281 in total) were collected and analyzed for cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-carboxylic acid (cis-Cl2CA and trans-Cl2CA), cis-3-(2,2-dibromo-vinyl)-2,2-dimethylcyclo-propanecarboxylic acid (Br2CA) and 3-phenoxybenzoic acid (3PBA) using a validated gas chromatography ion-trap mass spectrometry method. Only 3PBA was detectable in more than 60% of the collected samples enabling a reliable statistical analysis. Statistical analysis was performed to evaluate temporal variability in urinary excretion of 3PBA over the studied period. Both volume and creatinine (Cre) adjusted concentrations were evaluated with the latter one being the most reliable. Among all samples, first morning voids (FMV) were the least reproducible (interclass correlation coefficient – ICC, 0.551 and 0.350 for volume and creatinine adjusted concentrations, respectively). Spot and reconstructed 24-h samples were more reproducible in this study. ICC values for ng/mL concentrations were 0.599 and 0.681 (in spot and 24-h samples) and 0.846 and 0.796 for μg/g creatinine concentrations.Results of this study suggest fairly constant short-term exposure to pyrethroids metabolized to 3PBA among the urban population in Poland. Creatinine adjustment should be performed in epidemiological studies and spot or multiple spot samples should be preferentially collected for the highest reliability of the measurement.

Variation in urinary excretion of FDG, yet another uncertainty in quantitative PET

BackgroundThe standardized uptake value (SUV) is the most common estimate of metabolic activity used in clinical positron emission tomography (PET). Several biological and technological factors influence the accurate SUV calculation.PurposeTo assess another potential source of variability of the SUV, the variations in urinary excretion of fluorodeoxyglucose (FDG).Material and MethodsTwenty patients with various malignancies scheduled for PET/CT with 18F-FDG were included in the present study. The activity in urine voided immediately before image acquisition was measured and decay corrected. An estimation of FDG content in the urinary bladder was made during imaging, and the two components of urinary FDG were added. The urinary output of FDG, and the quantity of FDG divided by the time to measurements, was estimated.ResultsThe excretion of FDG in urine was between 5.7% and 15.2% of injected dose (decay corrected), and from 0.06% to 0.3%/min after injection, a five-fold difference in clearance.ConclusionAbout 10% of injected dose is excreted in urine at 70 min post injection, but the urinary FDG excretion was found to be highly variable, yet another uncertainty affecting the SUV measurements.

Bioavailability and catabolism of green tea flavan-3-ols in humans

Objective The aim of this study was to investigate green tea flavan-3-ol catabolism and plasma pharmacokinetic and urinary excretion by high-performance liquid chromatography with tandem mass spectrometry to evaluate their absolute bioavailability by taking into account all known and some unknown catabolites deriving from their interaction with the gastrointestinal tract and its host microflora. Methods A feeding study was carried out in 20 healthy human volunteers who ingested 400 mL of a ready-to-drink green tea containing approximately 400 μmol of flavan-3-ols. Urine and plasma were collected for 4 and 24 h, respectively, and 39 relevant catabolites were identified in these biological fluids by tandem mass spectrometry. Results In biological fluids, 39 relevant flavan-3-ol catabolites were identified. In plasma, (−)-epigallocatechin-3-gallate was the only unmetabolized compound and the highest in absolute concentration compared with (−)-epigallocatechin and (−)-epicatechin conjugates. Colonic microflora-derived polyhydroxyphenyl- γ-valerolactones were by far the main urinary catabolites, averaging 10 times greater concentratin than flavan-3-ol conjugates. The calculated bioavailability was equal to 39% and it is interesting to notice the great variability in urinary excretion of colonic metabolites among participants, probably related to differences in their own colonic microflora. Conclusion This study demonstrates that green tea catechins are more bioavailable than previously observed when colonic ring fission metabolites are taken into consideration. Regular consumption of ready-to-drink green tea containing flavan-3-ols allows a non-marginal exposure of the human body to these catabolites, somehow justifying the numerous beneficial actions described as linked to green tea intake.

Phenotyping Tea Consumers by Nutrikinetic Analysis of Polyphenolic End-Metabolites

An integration of metabolomics and pharmacokinetics (or nutrikinetics) is introduced as a concept to describe a human study population with different metabolic phenotypes following a nutritional intervention. The approach facilitates an unbiased analysis of the time-response of body fluid metabolites from crossover designed intervention trials without prior knowledge of the underlying metabolic pathways. The method is explained for the case of a human intervention study in which the nutrikinetic analysis of polyphenol-rich black tea consumption was performed in urine over a period of 48 h. First, multilevel PLS-DA analysis was applied to the urinary 1H NMR profiles to select the most differentiating biomarkers between the verum and placebo samples. Then, a one-compartment nutrikinetic model with first-order excretion, a lag time, and a baseline function was fitted to the time courses of these selected biomarkers. The nutrikinetic model used here fully exploits the crossover structure in the data by fitting the data from both the treatment period and the placebo period simultaneously. To demonstrate the procedure, a selected set of urinary biomarkers was used in the model fitting. These metabolites include hippuric acid, 4-hydroxyhippuric acid and 1,3-dihydroxyphenyl-2-O-sulfate and derived from microbial fermentation of polyphenols in the gut. Variations in urinary excretion between- and within the subjects were observed, and used to provide a phenotypic description of the test population.

Evaluation of urinary biomarkers of exposure to benzene: correlation with blood benzene and influence of confounding factors

trans,trans-Muconic acid (t,t-MA) is generally considered as a useful biomarker of exposure to benzene. However, because of its lack of specificity, concerns about its value at low level of exposure have recently been raised. The aim of this study was (a) to compare t,t-MA, S-phenylmercapturic acid (SPMA) and benzene (B-U) as urinary biomarkers of exposure to low levels of benzene in petrochemical workers and, (b) to evaluate the influence of sorbic acid (SA) and genetic polymorphisms of biotransformation enzymes on the excretion of these biomarkers. A total of 110 workers (including 24 smokers; 2-10 cigarettes/day) accepted to take part in the study. To assess external exposure to benzene, air samples were collected during the whole working period by a passive sampling device attached close to the breathing zone of 98 workers. Benzene was measured in blood (B-B) samples taken at the end of the shift, and was considered as the reference marker of internal dose. Urine was collected at the end of the shift for the determination of B-U, SPMA, t,t-MA, SA and creatinine (cr). B-U and B-B were determined by head-space/GC-MS, SPMA and SA by LC-MS, t,t-MA by HPLC-UV. Most (89%) personal measurements of airborne benzene were below the limit of detection (0.1 ppm); B-B ranged from <0.10 to 13.58 mug/l (median 0.405 microg/l). The median (range) concentrations of the urinary biomarkers were as follows: B-U 0.27 microg/l (<0.10-5.35), t,t-MA 0.060 mg/l (<0.02-0.92), SPMA 1.40 microg/l (0.20-14.70). Urinary SA concentrations ranged between <3 and 2,211 microg/l (median 28.00). Benzene concentration in blood and in urine as well as SPMA, but not t,t-MA, were significantly higher in smokers than in non-smokers. The best correlation between B-B and urinary biomarkers of exposure were obtained with benzene in urine (microg/l r = 0.514, P < 0.001; microg/g cr r = 0.478, P < 0.001) and SPMA (microg/l r = 0.495, P < 0.001; microg/g cr r = 0.426, P < 0.001) followed by t,t-MA (mg/l r = 0.363, P < 0.001; mg/g cr r = 0.300, P = 0.002). SA and t,t-MA were highly correlated (r = 0.618, P < 0.001; corrected for cr r = 0.637). Multiple linear regression showed that the variation of t,t-MA was mostly explained by SA concentration in urine (30% of the explained variance) and by B-B (12%). Variations of SPMA and B-U were explained for 18 and 29%, respectively, by B-B. About 30% of the variance of B-U and SPMA were explained by B-B and smoking status. Genetic polymorphisms for biotransformation enzymes (CYP2E1, EPHX1, GSTM1, GSTT1, GSTP1) did not significantly influence the urinary concentration of any of the three urinary biomarkers at this low level of exposure. At low levels of benzene exposure (<0.1 ppm), (1) t,t-MA is definitely not a reliable biomarker of benzene exposure because of the clear influence of SA originating from food, (2) SPMA and B-U reflect the internal dose with almost similar accuracies, (3) genetically based inter-individual variability in urinary excretion of biomarkers seems negligible. It remains to assess which biomarker is the best predictor of health effects.

Urinary excretion of kaempferol from common beans (Phaseolus vulgaris L.) in humans

The aim of this study was to assess kaempferol bioavailability in healthy humans, after bean (Phaseolus vulgaris L.) consumption through the monitoring of the excretion in relation to intake. In seven healthy subjects receiving kaempferol from cooked bean, maximum excretion of hydrolysed flavonol was obtained after 2–8 h. Intersexual variations in urinary excretion were found to be 6.10±5.50% and 5.40±5.40% of the kaempferol dose for male and female subjects, respectively. Although a 6.72-fold inter-individual variation between the highest and lowest excretion concentrations was found, all individuals exhibited similar excretion profiles. Moreover, a direct correlation between the percentage of kaempferol excreted and the body mass index of volunteers was observed with a correlation index equal to 0.80. All except two individuals exhibited a first peak of kaempferol excretion 2 h after ingestion. The study reveals information about inter-individual excretion capacity after kaempferol intake and that kaempferol can be used as a biomarker for flavonol consumption.

Biomonitoring for Chromium and Arsenic in Timber Treatment Plant Workers Exposed to CCA Wood Preservatives

This study reports a survey of occupational exposure to copper chrome arsenic (CCA) based wood preservatives during vacuum pressure timber impregnation. The survey involved biological monitoring based on analysis of chromium and arsenic in urine samples collected from UK workers. The aim of the study was to determine the extent of occupational exposure to arsenic and chromium in the UK timber treatment industry. The objectives were to collect and analyse urine samples from as many workers as possible, where CCA wood preservatives might be used, at 6 monthly intervals for 2 years. In addition, to investigate day-to-day variations in urinary excretion of chrome and arsenic by collecting and analysing three samples a week for 3 weeks in subsets of workers and controls (people not occupationally exposed). All urine samples were analysed for chromium and inorganic arsenic. To investigate any residual interference every sample was accompanied by a short questionnaire about recent consumption of seafood and smoking. The analytical methods for arsenic used a hydride generation technique to reduce interference from dietary sources of arsenic and also a technique that would measure total arsenic concentration in urine. The main findings show that workers exposed to CCA wood preservatives have concentrations of inorganic arsenic and chromium in urine that are significantly higher than those from non-occupationally exposed people but below biological monitoring guidance values that would indicate inhalation exposure at UK occupational exposure limits for chromium and arsenic. The effects of consumption of seafood on urinary arsenic were not significant using the hydride generation method for inorganic arsenic but were significant if 'total' arsenic was measured. The 'total' arsenic method could not distinguish CCA workers from controls and is clearly unsuitable for assessment of occupational exposure to arsenic. There was a significant increase in the urinary concentration of chromium in workers over the four sample collection rounds indicating increasing exposure to chromium during the 2 years of the study. This unexpected finding may be worth further investigation. Overall, the study demonstrated the utility of biological monitoring for assessment of occupational exposure to chromium and arsenic.

W13-P-009 Circadian variation in urinary excretion of TNF α and its soluble receptors in type 1 diabetes mellitus

W13-P-009 Circadian variation in urinary excretion of TNF α and its soluble receptors in type 1 diabetes mellitus