Bisphenol A and Bisphenol S in Hemodialyzers.

Bisphenol A (BPA)-based materials are used in the manufacturing of hemodialyzers, including their polycarbonate (PC) housings and polysulfone (PS) membranes. As concerns for BPA's adverse health effects rise, the regulation on BPA exposure is becoming more rigorous. Therefore, BPA alternatives, such as Bisphenol S (BPS), are increasingly used. It is important to understand the patient risk of BPA and BPS exposure through dialyzer use during hemodialysis. Here, we report the bisphenol levels in extractables and leachables obtained from eight dialyzers currently on the market, including high-flux and medium cut-off membranes. A targeted liquid chromatography-mass spectrometry strategy utilizing stable isotope-labeled internal standards provided reliable data for quantitation with the standard addition method. BPA ranging from 0.43 to 32.82 µg/device and BPS ranging from 0.02 to 2.51 µg/device were detected in dialyzers made with BPA- and BPS-containing materials, except for the novel FX CorAL 120 dialyzer. BPA and BPS were also not detected in bloodline controls and cellulose-based membranes. Based on the currently established tolerable intake (6 µg/kg/day), the resulting margin of safety indicates that adverse effects are unlikely to occur in hemodialysis patients exposed to BPA and BPS quantified herein. With increasing availability of new data and information about the toxicity of BPA and BPS, the patient safety limits of BPA and BPS in those dialyzers may need a re-evaluation in the future.

Toxicological risk assessment of bisphenol a released from dialyzers under simulated-use and exaggerated extraction conditions.

Bisphenol A (BPA) belongs to a group of chemicals used in the production of polycarbonate, polysulfone, and polyethersulfone which are used, among other applications, in the manufacture of dialyzers. While exposure to BPA is widespread in the general population, dialysis patients represent a population with potentially chronic parenteral BPA exposures. To assess the potential risk of BPA exposure to dialysis patients through dialyzer use, exposure estimates were calculated based on BPA levels measured by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry following extractions from dialyzers manufactured by Fresenius Medical Care. Extraction conditions included both simulated-use leaching and exaggerated extractions to evaluate possible leachable and extractable BPA, respectively, from the devices. The mean BPA concentrations were 3.6 and 108.9 ppb from simulated-use and exaggerated extractions, respectively, from polycarbonate-containing dialyzers. No BPA was detected from polypropylene-containing dialyzers. Margins of Safety (MOS) were calculated to evaluate the level of risk to patients from estimated BPA exposure from the dialyzers, and the resulting MOS were 229 and 45 for simulated-use and exaggerated extractions, respectively. The findings suggest that there is an acceptable level of toxicological risk to dialysis patients exposed to BPA from use of the dialyzers tested in the current study.

Hepatic Transporter Expression in Metabolic Syndrome: Phenotype, Serum Metabolic Hormones, and Transcription Factor Expression.

Metabolic syndrome is a multifactorial disease associated with obesity, insulin resistance, diabetes, and the alteration of multiple metabolic hormones. Obesity rates have been rising worldwide, which increases our need to understand how this population will respond to drugs and exposure to other chemicals. The purpose of this study was to determine in lean and obese mice the ontogeny of clinical biomarkers such as serum hormone and blood glucose levels as well as the physiologic markers that correlate with nuclear receptor- and transporter-related pathways. Livers from male and female wild-type (WT) (C57BL/6) and ob/ob mice littermates were collected before, during, and after the onset of obesity. Serum hormone and mRNA levels were analyzed. Physiologic changes and gene expression during maturation and progression to obesity were performed and correlation analysis was performed using canonical correlations. Significant ontogenic changes in both WT and ob/ob mice were observed and these ontogenic changes differ in ob/ob mice with the development of obesity. In males and females, the ontogenic pattern of the expression of genes such as Abcc3, 4, Abcg2, Cyp2b10, and 4a14 started to differ from week 3, and became significant at weeks 4 and 8 in ob/ob mice compared with WT mice. In obese males, serum resistin, glucagon, and glucose levels correlated with the expression of most hepatic ATP-binding cassette (Abc) transporters, whereas in obese females, serum glucagon-like peptide 1 levels were correlated with most hepatic uptake transporters and P450 enzymes. Overall, the correlation between physiologic changes and gene expression indicate that metabolism-related hormones may play a role in regulating the genes involved in drug metabolism and transport.

Chronic activation of FXR in transgenic mice caused perinatal toxicity and sensitized mice to cholesterol toxicity.

The nuclear receptor farnesoid X receptor (FXR) (nuclear receptor subfamily 1, group H, member 4, or NR1H4) is highly expressed in the liver and intestine. Previous reports have suggested beneficial functions of FXR in the homeostasis of bile acids, lipids, and glucose, as well as in promoting liver regeneration and inhibiting carcinogenesis. To investigate the effect of chronic FXR activation in vivo, we generated transgenic mice that conditionally and tissue specifically express the activated form of FXR in the liver and intestine. Unexpectedly, the transgenic mice showed several intriguing phenotypes, including partial neonatal lethality, growth retardation, and spontaneous liver toxicity. The transgenic mice also displayed heightened sensitivity to a high-cholesterol diet-induced hepatotoxicity but resistance to the gallstone formation. The phenotypes were transgene specific, because they were abolished upon treatment with doxycycline to silence the transgene expression. The perinatal toxicity, which can be rescued by a maternal vitamin supplement, may have resulted from vitamin deficiency due to low biliary bile acid output as a consequence of inhibition of bile acid formation. Our results also suggested that the fibroblast growth factor-inducible immediate-early response protein 14 (Fn14), a member of the proinflammatory TNF family, is a FXR-responsive gene. However, the contribution of Fn14 induction in the perinatal toxic phenotype of the transgenic mice remains to be defined. Because FXR is being explored as a therapeutic target, our results suggested that a chronic activation of this nuclear receptor may have an unintended side effect especially during the perinatal stage.

Fasting induces nuclear factor E2-related factor 2 and ATP-binding Cassette transporters via protein kinase A and Sirtuin-1 in mouse and human.

AIMS: The purpose of this study was to determine whether 3'-5'-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) and Sirtuin-1 (SIRT1) dependent mechanisms modulate ATP-binding Cassette (ABC) transport protein expression. ABC transport proteins (ABCC2-4) are essential for chemical elimination from hepatocytes and biliary excretion. Nuclear factor-E2 related-factor 2 (NRF2) is a transcription factor that mediates ABCC induction in response to chemical inducers and liver injury. However, a role for NRF2 in the regulation of transporter expression in nonchemical models of liver perturbation is largely undescribed. RESULTS: Here we show that fasting increased NRF2 target gene expression through NRF2- and SIRT1-dependent mechanisms. In intact mouse liver, fasting induces NRF2 target gene expression by at least 1.5 to 5-fold. In mouse and human hepatocytes, treatment with 8-Bromoadenosine-cAMP, a cAMP analogue, increased NRF2 target gene expression and antioxidant response element activity, which was decreased by the PKA inhibitor, H-89. Moreover, fasting induced NRF2 target gene expression was decreased in liver and hepatocytes of SIRT1 liver-specific null mice and NRF2-null mice. Lastly, NRF2 and SIRT1 were recruited to MAREs and Antioxidant Response Elements (AREs) in the human ABCC2 promoter. INNOVATION: Oxidative stress mediated NRF2 activation is well described, yet the influence of basic metabolic processes on NRF2 activation is just emerging. CONCLUSION: The current data point toward a novel role of nutrient status in regulation of NRF2 activity and the antioxidant response, and indicates that cAMP/PKA and SIRT1 are upstream regulators for fasting-induced activation of the NRF2-ARE pathway.

Cholesterol sulfate and cholesterol sulfotransferase inhibit gluconeogenesis by targeting hepatocyte nuclear factor 4α.

Sulfotransferase (SULT)-mediated sulfation represents a critical mechanism in regulating the chemical and functional homeostasis of endogenous and exogenous molecules. The cholesterol sulfotransferase SULT2B1b catalyzes the sulfoconjugation of cholesterol to synthesize cholesterol sulfate (CS). In this study, we showed that the expression of SULT2B1b in the liver was induced in obese mice and during the transition from the fasted to the fed state, suggesting that the regulation of SULT2B1b is physiologically relevant. CS and SULT2B1b inhibited gluconeogenesis by targeting the gluconeogenic factor hepatocyte nuclear factor 4α (HNF4α) in both cell cultures and transgenic mice. Treatment of mice with CS or transgenic overexpression of the CS-generating enzyme SULT2B1b in the liver inhibited hepatic gluconeogenesis and alleviated metabolic abnormalities both in mice with diet-induced obesity (DIO) and in leptin-deficient (ob/ob) mice. Mechanistically, CS and SULT2B1b inhibited gluconeogenesis by suppressing the expression of acetyl coenzyme A (acetyl-CoA) synthetase (Acss), leading to decreased acetylation and nuclear exclusion of HNF4α. Our results also suggested that leptin is a potential effector of SULT2B1b in improving metabolic function. We conclude that SULT2B1b and its enzymatic by-product CS are important metabolic regulators that control glucose metabolism, suggesting CS as a potential therapeutic agent and SULT2B1b as a potential therapeutic target for metabolic disorders.

Alcohol cirrhosis alters nuclear receptor and drug transporter expression in human liver.

Unsafe use of alcohol results in approximately 2.5 million deaths worldwide, with cirrhosis contributing to 16.6% of reported deaths. Serum insulin levels are often elevated in alcoholism and may result in diabetes, which is why alcoholic liver disease and diabetes often are present together. Because there is a sizable population with these diseases alone or in combination, the purpose of this study was to determine whether transporter expression in human liver is affected by alcoholic cirrhosis, diabetes, and alcoholic cirrhosis coexisting with diabetes. Transporters aid in hepatobiliary excretion of many drugs and toxic chemicals and can be determinants of drug-induced liver injury. Drug transporter expression and transcription factor-relative mRNA and protein expression in normal, diabetic, cirrhotic, and cirrhosis with diabetes human livers were quantified. Cirrhosis significantly increased ABCC4, 5, ABCG2, and solute carrier organic anion (SLCO) 2B1 mRNA expression and decreased SLCO1B3 mRNA expression in the liver. ABCC1, 3-5, and ABCG2 protein expression was also upregulated by alcoholic cirrhosis. ABCC3-5 and ABCG2 protein expression was also upregulated in diabetic cirrhosis. Cirrhosis increased nuclear factor E2-related factor 2 mRNA expression, whereas it decreased pregnane-X-receptor and farnesoid-X-receptor mRNA expression in comparison with normal livers. Hierarchical cluster analysis indicated that expressions of ABCC2, 3, and 6; SLCO1B1 and 1B3; and ABCC4 and 5 were more closely related in the livers from this cohort. Overall, alcoholic cirrhosis altered transporter expression in human liver.

Constitutive activation of nuclear factor-E2-related factor 2 induces biotransformation enzyme and transporter expression in livers of mice with hepatocyte-specific deletion of Kelch-like ECH-associated protein 1.

Chemicals that activate nuclear factor-E2-related factor 2 (Nrf2) often increase multidrug-resistance-associated protein (Mrp) expression in liver. Hepatocyte-specific deletion of Kelch-like ECH-associated protein 1 (Keap1) activates Nrf2. Use of hepatocyte-specific Keap1 deletion represents a nonpharmacological method to determine whether constitutive Nrf2 activation upregulates liver transporter expression in vivo. The mRNA, protein expression, and localization of several biotransformation and transporters were determined in livers of wild-type and hepatocyte-specific Keap1-null mice. Sulfotransferase 2a1/2, NADP(H):quinone oxidoreductase 1, cytochrome P450 2b10, 3a11, and glutamate-cysteine ligase catalytic subunit expression were increased in livers of Keap1-null mice. Organic anion-transporting polypeptide 1a1 expression was nearly abolished, as compared to that detected in livers of wild-type mice. By contrast, Mrp 1-5 mRNA and protein levels were increased in Keap1-null mouse livers, with Mrp4 expression being more than 15-fold higher than wild types. In summary, Nrf2 has a significant role in affecting Oatp and Mrp expressions.

Pregnane X receptor as a therapeutic target to inhibit androgen activity.

The androgen-androgen receptor signaling pathway plays an important role in the pathogenesis of prostate cancer. Accordingly, androgen deprivation has been the most effective endocrine therapy for hormone-dependent prostate cancer. Here, we report a novel pregnane X receptor (PXR)-mediated and metabolism-based mechanism to reduce androgenic tone. PXR is a nuclear receptor previously known as a xenobiotic receptor regulating the expression of drug metabolizing enzymes and transporters. We showed that genetic (using a PXR transgene) or pharmacological (using a PXR agonist) activation of PXR lowered androgenic activity and inhibited androgen-dependent prostate regeneration in castrated male mice that received daily injections of testosterone propionate by inducing the expression of cytochrome P450 (CYP)3As and hydroxysteroid sulfotransferase (SULT)2A1, which are enzymes important for the metabolic deactivation of androgens. In human prostate cancer cells, treatment with the PXR agonist rifampicin (RIF) inhibited androgen-dependent proliferation of LAPC-4 cells but had little effect on the growth of the androgen-independent isogenic LA99 cells. Down-regulation of PXR or SULT2A1 in LAPC-4 cells by short hairpin RNA or small interfering RNA abolished the RIF effect, indicating that the inhibitory effect of RIF on androgens was PXR and SULT2A1 dependent. In summary, we have uncovered a novel function of PXR in androgen homeostasis. PXR may represent a novel therapeutic target to lower androgen activity and may aid in the treatment and prevention of hormone-dependent prostate cancer.

Minireview: Nuclear receptor-controlled steroid hormone synthesis and metabolism.

Steroid hormones are essential in normal physiology whereas disruptions in hormonal homeostasis represent an important etiological factor for many human diseases. Steroid hormones exert most of their functions through the binding and activation of nuclear hormone receptors (NRs or NHRs), a superfamily of DNA-binding and often ligand-dependent transcription factors. In recent years, accumulating evidence has suggested that NRs can also regulate the biosynthesis and metabolism of steroid hormones. This review will focus on the recent progress in our understanding of the regulatory role of NRs in hormonal homeostasis and the implications of this regulation in physiology and diseases.

Perchlorate in wet deposition across North America.

Natural perchlorate is believed to be of atmospheric origin, yet no systematic study has been conducted to evaluate perchlorate deposition rate and possible seasonal or spatial variations. This study evaluated perchlorate concentrations in weekly composite wet deposition samples acquired through the National Atmospheric Deposition Program from 26 sites across the continental United States, Alaska, and Puerto Rico for a 1-3 year period. Perchlorate concentrations varied from <5 ng/L to a high of 102 ng/L with a mean of 14.1 +/- 13.5 ng/L for the 1578 total samples. The annual perchlorate flux by site ranged from a low of 12.5 (TX) to 157 mg/ha-year (NE) and averaged 65 +/- 30 mg/ha-year for all sites. Perchlorate concentrations and flux in wet deposition were generally highest in May-August declining to lows in December-February. Average annual perchlorate flux was correlated (r > 0.5; p < 0.001) with Ca2+, K+, NH4+, NO3(-), Cl(-), and SO4(-2). Wet deposition rate of ClO4(-) in the conterminous United States (excluding Alaska, Hawaii, and Puerto Rico) while diffuse, represents a potential annual net mass flux of 51,000 kg, a value comparable to the estimated annual environmental releases from other known ClO4(-) sources.

Drug-metabolizing enzyme and transporter expression in a mouse model of diabetes and obesity.

Obesity and type II diabetes pose a serious human health risk. Obese or diabetic patients usually take prescription drugs that require hepatic and renal metabolism and transport, and these patients sometimes display different pharmacokinetics of these drugs. Therefore, mRNA and protein expression of drug-metabolizing enzymes (DMEs) and transporters was measured in livers and kidneys of adult wild-type and ob/ob mice, which model obesity and diabetes. mRNA expression of numerous DMEs increased by at least 2-fold in livers of male ob/ob mice, including Cyp4a14, Cyp2b10, NAD(P)H:quinone oxidoreductase 1 (Nqo1), and sulfotransferase 2a1/2. In general, expression of uptake transporters was decreased in livers of ob/ob mice, namely organic anion-transporting polypeptides (Oatps) and sodium/taurocholate cotransporting polypeptide (Ntcp). In particular, Oatp1a1 mRNA and protein expression in livers of ob/ob mice was diminished to <5% and <15% of that in wild-types, respectively. Generally, the mRNA and protein expression of efflux transporters multidrug resistance-associated proteins (Mrps) was increased in livers of ob/ob mice, particularly with Mrp4 expression being elevated by at least 6-fold and Mrp2 expression at least 3-fold in livers of ob/ob mice. In kidney, Nqo1, Mrp3, 4, Oatp1a1, and organic anion transporter 2 (Oat2) showed significant alterations with mRNA expression levels in ob/ob mice, being increased for Nqo1 and Mrp4 and decreased for Mrp3, Oatp1a1, and Oat2. In summary, the expression of a number of DMEs and transporters was significantly altered in livers and kidneys of ob/ob mice. Since expression of some DMEs and transporters is regulated similarly between mouse and human, the data from this study suggest that transporter expression in liver and kidney may be changed in patients presenting with obesity and/or type II diabetes.

Fatty acid profile in milk from goats, Capra aegagrus hircus, exposed to perchlorate and its relationship with perchlorate residues in human milk.

Polyunsaturated fatty acids (PUFA) in milk are vital for normal growth and development of infant mammals. Changes in fatty acid composition were observed in milk fat from goats dosed with perchlorate (0.1 and 1 mg/kg body weight/day) for 31 days, but the effect was not persistent. Adaptation may be induced in these goats to compensate for the perchlorate effect. In an analysis of fatty acid composition in human milk samples, a weak negative correlation was observed between perchlorate concentrations and total PUFA in 38 human milk samples.

Effects of perchlorate on sodium-iodide symporter and pendrin gene expression in deer mice.

Effects of perchlorate on sodium-iodide symporter (NIS) and pendrin gene expression in deer mice kidney and stomach were investigated. This was accomplished by isolating a partial cDNA sequence of deer mice NIS gene of 425 bps, and quantitatively analyzing NIS mRNA expression in various deer mouse tissues. The highest NIS expression level was in the stomach, followed by testes, brain, and large intestine; very low expression of NIS was observed in the lung, kidney, heart, and liver. Exposure to perchlorate through drinking water for 28 days did not significantly increase NIS gene expression in the kidney and stomach, and pendrin gene expression in the kidney. In a depuration experiment in which deer mice were exposed to perchlorate for 8-h followed by an 88-h depuration period, no significant difference was observed between the low and high exposure groups in terms of NIS or pendrin gene expression in the kidney or stomach at the end of the experiment. Furthermore, no significant linear relationship was observed between gene expression (either NIS or pendrin) in the kidney and perchlorate mass excreted via urine at day 28, average daily excretion, or total excretion mass over the 28 day exposure. Several factors could influence the effect of perchlorate exposure on NIS and pendrin gene expression in the stomach and kidney, including (1) pre-exposure to trace perchlorate through food and water perhaps resulting in adaptation (or tolerance) in these animals; (2) metabolism of perchlorate in deer mice causing only 46-61% perchlorate excreted into urine. It is also possible that there is no effect of perchlorate exposure and/or urinary excretion on NIS and pendrin gene expression, particularly in the kidney.

Uptake, accumulation and depuration of sodium perchlorate and sodium arsenate in zebrafish (Danio rerio).

In toxicokinetics studies, interactions between chemicals in mixtures has been largely neglected. This study examines a mixture of perchlorate and arsenate because (1) they have the potential to co-occur in contaminated aquatic habitats, and (2) a previous study by the authors found possible toxicological interactive effects. In the present study, zebrafish (Danio rerio) were exposed to two concentrations of sodium perchlorate (10 and 100 mg l(-1)), sodium arsenate (1 and 10 mg l(-1)), and the mixture-sodium perchlorate+sodium arsenate (10+1 mg l(-1) and 100+10 mg l(-1) Na(2)HAsO(4)-high mixture) for 90 d. Their uptake and accumulation by zebrafish was evaluated at 10, 30, 60, and 90 d. In addition, depuration was examined at 1, 3, and 5d after cessation of the exposure. The uptake of either chemical was concentration-dependent, with significantly higher uptake at high concentrations at either exposure interval. In contrast, there was no significant difference in whole body residue between single chemicals and the corresponding mixture except for 100 mg l(-1) sodium arsenate at 90 d. However, there was increasing accumulation over time at the high concentration of either chemical alone and their mixture, and this increasing trend was more pronounced in the single chemical exposures than in the mixture. At the concentrations tested in the current study, both chemicals reduced the uptake but enhanced the depuration of the other chemical from the zebrafish. This study represents the first examination of the interaction of two anions-perchlorate and arsenate with respect to toxicokinetics.

Effects of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) metabolites on cricket (Acheta domesticus) survival and reproductive success.

The effect of two major hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) metabolites, hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX), on cricket (Acheta domesticus) survival and reproduction was studied. RDX metabolites did not have adverse effects on cricket survival, growth, and egg production. However, MNX and TNX did affect egg hatching. MNX and TNX were more toxic in spiked-sand than in topical tests. TNX was more toxic to egg than MNX. Developmental stage and exposure time affected hatching. After 30 days exposure to MNX or TNX, the EC20, EC50, and EC95 were 47, 128, and 247 microg/g for TNX, and 65, 140, and 253 microg/g for MNX in topical tests. The ECs for 20, 50, and 95 were 21, 52, and 99 microg/g for MNX, and 12, 48, and 97 microg/g for TNX in sand. No gross abnormalities in cricket nypmhs were observed in all experiments indicating that neither TNX or MNX is teratogenic in this assay.

Optimization of operating conditions for the determination of perchlorate in biological samples using preconcentration/preelution ion chromatography.

Perchlorate originates as a contaminant in the environment from the use of salts in the manufacture of solid rocket fuels and munitions. Monitoring potential perchlorate contamination in the environment is of interest, however, very few analytical methods have been developed for perchlorate determination in biological samples. Analysis of complex samples by ion chromatography is complicated by matrix components that can interfere with perchlorate determination. However, a recently developed preconcentration/preelution (PC/PE) ion chromatography method has demonstrated the capability to analyze certain complex samples such as high salinity water, milk, and hydroponic fertilizers. The ability of this method to reduce sample background and lower detection limits in ion chromatography for various biological samples was evaluated in this study. The PC/PE method was applicable to the analysis of kidneys, livers, zebrafish, quail eggs, lettuce, and urine. Optimal operating conditions were determined for each matrix. Ranges of optimal wash volumes were shorter when 15 mM NaOH prewash solutions were used compared with 10mM and good recovery was achieved for most matrices with an injection period > or =60s. Prewash solution concentration did not appear to significantly affect matrix background. The PC/PE method was capable of reducing sample background when compared to EPA Method 314.0, which resulted in detection limits, with the exception of zebrafish and urine, that were two-fold lower than those achieved with EPA Method 314.0.

Challenges in determining perchlorate in biological tissues and fluids: implications for characterizing perchlorate exposure.

The ability to measure environmental contaminants in biological tissues and fluids is important in the characterization of exposure. However, the analysis of certain contaminants in these matrices presents significant challenges. Perchlorate (ClO4-) has emerged as a potential contaminant of concern primarily in drinking water and also in contaminated food. Significant advances have been made in the analysis of perchlorate in environmental matrices (water, soil) by ion chromatography (IC). In contrast, the analysis of perchlorate in extracts of biological tissues and fluids (vegetation, organs, milk, blood, urine, etc.) presents several challenges including small sample sizes, extracts with high matrix conductivity, and co-elution of other ions during IC analysis. To be able to detect low concentrations of perchlorate in biological samples, interferences must be removed or minimized, such as through the use of preparative chromatography cleanup techniques and/or alternative analytical methods less susceptible to common interferences (preconcentration or mass spectrometric detection). We present discussion and examples of the challenges encountered in the analysis of tissue extracts and fluids for perchlorate by IC and how some of those analytical challenges have been overcome.

A cleanup method for perchlorate determination in urine.

There is increasing concern about perchlorate exposure because of perchlorate's potential effects on organisms as a thyroid hormone disruptor, as well as its contamination of the environment being much more widespread than previously thought. Perchlorate is excreted primarily into urine, therefore, evaluating perchlorate residues in urine should be a reasonable approach for determining exposure and if successful could be used as an effective biomarker of perchlorate exposure. Since the presence of ions and other biomolecules in matrices like urine usually confounds accurate determination of perchlorate by ion chromatography, it is necessary to develop efficient methods for perchlorate determination in these matrices. We developed a method that reduces the background signal of urine, which is typically the problem with the analysis of biological fluids and tissues by ion chromatography. Relatively high recovery of perchlorate was shown. In cow urine samples spiked with perchlorate at 2.5, 10, and 100mug/L, perchlorate recoveries were 67%+/-2.5, 77%+/-3.6, and 81%+/-1.7 (mean+/-S.D.), respectively. In addition, the detection limit was as low as 12.6, 12.3, and 18.7mug/L in cow, vole, and human urine samples, respectively.

A study on perchlorate exposure and absorption in beef cattle.

Perchlorate exposure and potential effects were evaluated in large mammals by monitoring heifer calves placed on a site with access to streamwater fed by a perchlorate-contaminated groundwater spring ( approximately 25 ng/mL). Blood was collected from the two calves on the site (and two control calves from an uncontaminated site) approximately every 2 weeks for analysis of perchlorate residues and thyroid hormones. During the 14 week study, perchlorate was detected (detection limit = 13.7 ng/mL) in blood plasma twice (15 ng/mL and 22 ng/mL) in one of the heifer calves drinking perchlorate-contaminated water on consecutive sampling periods 4 and 6 weeks after the beginning of perchlorate exposure. Constant exposure to 25 ppb perchlorate in drinking water had no effect on circulating thyroid hormones (T(3) and T(4)) in the heifer calves.