Determination of bisphenol A in rat brain by microdialysis and column switching high-performance liquid chromatography with fluorescence detection

Warning against co-administration of 3,4-methylenedioxymethamphetamine (MDMA) with methamphetamine from the perspective of pharmacokinetic and pharmacodynamic evaluations in rat brain

3,4-Methylenedioxymethamphetamine (MDMA) and methamphetamine often cause serious adverse effects (e.g., rhabdomyolysis, and cardiac disease) following hyperthermia triggered by release of brain monoamines such as dopamine and serotonin. Therefore, evaluation of brain monoamine concentrations is useful to predict these drugs' risks in human. This study aimed to evaluate risks of co-administration of MDMA and methamphetamine, both of which are abused frequently in Japan, based on drug distribution and monoamine level in the rat brain. Rats were allocated to three groups: (1) sole MDMA administration (12 or 25 mg/kg, intraperitoneally), (2) sole methamphetamine administration (10 mg/kg, intraperitoneally) and (3) co-administration of MDMA (12 mg/kg, intraperitoneally) and methamphetamine (10 mg/kg, intraperitoneally). We monitored pharmacokinetic and pharmacodynamic variables for drugs and monoamines in the rat brain. Area under the curve for concentration vs. time until 600 min from drug administration (AUC₀₋₆₀₀) increased from 348.0 to 689.8 μgmin/L for MDMA and from 29.9 to 243.4 μMmin for dopamine in response to co-administration of methamphetamine and MDMA compared to sole MDMA (12 mg/kg) administration. After sole methamphetamine or that with MDMA administration, AUC₀₋₆₀₀ of methamphetamine were 401.8 and 671.1 μgmin/L, and AUC₀₋₆₀₀ of dopamine were 159.9 and 243.4 μMmin. In conclusion, the brain had greater exposure to MDMA, methamphetamine and dopamine after co-administration of MDMA and methamphetamine than when these two drugs were given alone. This suggests co-administration of MDMA with methamphetamine confers greater risk than sole administration, and that adverse events of MDMA ingestion may increase when methamphetamine is co-administered.

Mechanisms affecting neuroendocrine and epigenetic regulation of body weight and onset of puberty: potential implications in the child born small for gestational age (SGA)

Signaling peptides produced in peripheral tissues such as gut, adipose tissue, and pancreas communicate with brain centers, such as hypothalamus and hindbrain to manage energy homeostasis. These regulatory mechanisms of energy intake and storage have evolved during long periods of hunger in the evolution of man to protect the species from extinction. It is now clear that these circuitries are influenced by prenatal and postnatal environmental factors including endocrine disruptive chemicals. Hypothalamic appetite regulatory systems develop and mature in utero and early infancy, and involve signaling pathways that are important also for the regulation of puberty onset. Recent studies in humans and animals have shown that metabolic pathways involved in regulation of growth, body weight gain and sexual maturation are largely affected by epigenetic programming that can impact both current and future generations. In particular, intrauterine and early infantile developmental phases of high plasticity are susceptible to factors that affect metabolic programming that therefore, affect metabolic function throughout life. In children born small for gestational age, poor nutritional conditions during gestation can modify metabolic systems to adapt to expectations of chronic undernutrition. These children are potentially poorly equipped to cope with energy-dense diets and are possibly programmed to store as much energy as possible, leading to later obesity, metabolic syndrome, disturbed regulation of normal puberty and early onset of cardiovascular disease. Most cases of disturbed energy balance are likely a result of a combination of genetics, epigenetics and environment. This review will discuss potential mechanisms linking intrauterine growth retardation with changes in growth, energy homeostasis and sexual maturation.

Analytical and biological methods for probing the blood-brain barrier

The blood-brain barrier (BBB) is an important interface between the peripheral and central nervous systems. It protects the brain against the infiltration of harmful substances and regulates the permeation of beneficial endogenous substances from the blood into the extracellular fluid of the brain. It can also present a major obstacle in the development of drugs that are targeted for the central nervous system. Several methods have been developed to investigate the transport and metabolism of drugs, peptides, and endogenous compounds at the BBB. In vivo methods include intravenous injection, brain perfusion, positron emission tomography, and microdialysis sampling. Researchers have also developed in vitro cell-culture models that can be employed to investigate transport and metabolism at the BBB without the complication of systemic involvement. All these methods require sensitive and selective analytical methods to monitor the transport and metabolism of the compounds of interest at the BBB.

Spectrofluorimetric determination of sertraline in dosage forms and human plasma through derivatization with 9-fluorenylmethyl chloroformate

BACKGROUND

Sertraline is primarily used to treat major depression in adult outpatients as well as obsessive-compulsive, panic and social anxiety disorders in both adults and children. A survey of the literature reveals that most of the reported methods are either insufficiently sensitive or tedious and require highly sophisticated and dedicated instrumentation. The proposed method is considered to be specific for determination of SER in presence of its metabolite (deaminated form).

RESULTS

A sensitive, simple and specific spectrofluorimetric method was developed for the determination of sertraline (SER) in pharmaceutical formulations and biological fluids. The method is based on its reaction with 9-fluorenylmethyl chloroformate (FMOC-Cl) in borate buffer of pH 8.0 to yield a highly fluorescent derivative peaking at 315 nm after excitation at 265 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence concentration plot was rectilinear over the range of 0.05-1.0 μg mL-1 with a lower detection limit of 5.34 × 10-3 μg mL-1 and limit of quantitation of 0.016 μg mL-1.

CONCLUSIONS

The proposed method was successfully applied to the analysis of commercial tablets and the results obtained were in good agreement with those obtained using the reference method. Furthermore, the method was applied for the determination of SER in spiked and real human plasma. The mean % recovery (n = 3) was 94.33 ± 1.53 and 92.00 ± 2.65, respectively. A proposal of the reaction pathway was postulated.

Exposure to bisphenol A appears to impair hippocampal neurogenesis and spatial learning and memory

Bisphenol A (BPA) is widely used in the manufacture of plastics and epoxy resins, and is known to affect reproductive organ growth and development. However, the effects of BPA on hippocampal neurogenesis are unclear in young adult mice. Therefore, the present study was conducted to examine the effects of BPA on hippocampal neurogenesis and learning as well as memory performance in young adult mice. BPA (1, 5, and 20 mg/kg/day) was administered orally to mice for 2 weeks. It was found that high-dose BPA (20 mg/kg/day) decreased the number of newly generated cells in hippocampus, but that low-dose BPA (1 mg/kg) increased the survival of newly generated cells in hippocampi of young mice. Furthermore, high-dose BPA (20mg/kg/day) was found to impair learning and memory performance significantly. However, no significant differences were observed between high- and low-dose treated mice in terms of levels of brain-derived neurotrophic factor (BDNF) or reactive oxygen species production in hippocampus. In addition, BPA treatment did not induce neuronal loss or damage or astrocyte activation. These data suggest that exposure to BPA causes fluctuations in hippocampal neurogenesis in young adult mice that result in spatial learning and memory impairment via a BDNF-independent pathway.

Distribution of bisphenol A into tissues of adult, neonatal, and fetal Sprague-Dawley rats

Bisphenol A (BPA) is an important industrial chemical used in the manufacture of polycarbonate plastic products and epoxy resin-based food can liners. The presence of BPA metabolites in urine of >90% of Americans aged 6-60 suggests ubiquitous and frequent exposure in the range of 0.02-0.2μg/kgbw/d (25th-95th percentiles). The current study used LC/MS/MS to measure placental transfer and concentrations of aglycone (receptor-active) and conjugated (inactive) BPA in tissues from Sprague-Dawley rats administered deuterated BPA (100μg/kg bw) by oral and IV routes. In adult female rat tissues, the tissue/serum concentration ratios for aglycone BPA ranged from 0.7 in liver to 5 in adipose tissue, reflecting differences in tissue perfusion, composition, and metabolic capacity. Following IV administration to dams, placental transfer was observed for aglycone BPA into fetuses at several gestational days (GD), with fetal/maternal serum ratios of 2.7 at GD 12, 1.2 at GD 16, and 0.4 at GD 20; the corresponding ratios for conjugated BPA were 0.43, 0.65, and 3.7. These ratios were within the ranges observed in adult tissues and were not indicative of preferential accumulation of aglycone BPA or hydrolysis of conjugates in fetal tissue in vivo. Concentrations of aglycone BPA in GD 20 fetal brain were higher than in liver or serum. Oral administration of the same dose did not produce measurable levels of aglycone BPA in fetal tissues. Amniotic fluid consistently contained levels of BPA at or below those in maternal serum. Concentrations of aglycone BPA in tissues of neonatal rats decreased with age in a manner consistent with the corresponding circulating levels. Phase II metabolism of BPA increased with fetal age such that near-term fetus was similar to early post-natal rats. These results show that concentrations of aglycone BPA in fetal tissues are similar to those in other maternal and neonatal tissues and that maternal Phase II metabolism, especially following oral administration, and fetal age are critical in reducing exposures to the fetus.

Pharmacodynamic interactions between MDMA and concomitants in MDMA tablets on extracellular dopamine and serotonin in the rat brain

3,4-methylenedioxymethamphetamine (MDMA) is a psychoactive stimulant abused by young people as the recreational drug ecstasy. Other compounds, either deliberately added or present as byproducts, are often found in MDMA tablets and can unexpectedly interact with each other. The aim of this study was to evaluate the pharmacodynamic effects of interactions caused by concomitants in MDMA tablets on extracellular dopamine and serotonin (5-HT) by microdialysis in the striatum of ethylcarbamate-anesthetized rats. Baseline levels of dopamine and 5-HT in the striatum were 16.5±7.7 and 3.5±1.7 nM (mean±standard deviation), respectively. After a single administration of MDMA (10 mg/kg, i.p.), a dramatic increase in extracellular dopamine (Cmax: 36.1-fold vs. baseline) and 5-HT levels (Cmax: 9.3-fold vs. baseline) was observed. When rats were co-administered with methamphetamine (1, 5 or 10 mg/kg) with MDMA, the dopamine levels induced by MDMA increased in a methamphetamine-dose-dependent manner (Cmax: 2.5-, 3.5-, and 3.8-fold vs. MDMA). A similar trend was observed in 5-HT levels (Cmax: 1.1-, 1.3-, and 1.8-fold vs. MDMA). In contrast, ketamine and caffeine showed synergistic effects on the monoamine levels induced by MDMA, whereas the individual administration of either of these compounds did not affect monoamine levels. Ketamine (1, 5 mg/kg) decreased the dopamine levels induced by MDMA (Cmax: 0.9- and 0.7-fold vs. MDMA) and increased the 5-HT levels induced by MDMA (Cmax: 1.4- and 1.6-fold vs. MDMA), and co-administration of caffeine (20 mg/kg) with MDMA increased dopamine levels (Cmax: 1.7-fold vs. MDMA). These results suggest that exposure to multiple drugs in addition to MDMA can have neurotoxic effects.

Differential accumulation levels in the brain of rats exposed to the endocrine disruptor 4-tert-octylphenol (OP)

Octylphenol (OP) is an endocrine-disrupting chemical that accumulates in various organs. It has also been shown to exert noxious effects on the central nervous system. In the present study, we measured in Sprague-Dawley rats the degree of OP accumulation in different areas of the brain and investigated the effect of OP in pain modulation. Two groups of male Sprague-Dawley rats were treated for 20 days with 50mg/kg BW/day of OP (group 1) or vehicle (group 2). At the end of the treatment, the formalin test was performed to evaluate the effect of OP exposure on pain. Soon after, rats were sacrificed, and the accumulation of OP in the cerebral cortex, hippocampus, hypothalamus, cerebellum, thalamus, striatum, mesencephalus and ventral hindbrain was measured by HPLC analysis. The results showed a greater accumulation of OP in the cerebral cortex compared to all the other areas; there was also more accumulation in the cerebellum compared to the mesencephalus and thalamus. No accumulation was found in the striatum. These results suggest that there is a preferential accumulation of OP in different areas of the brain with consequences to neural behaviour. On the contrary, experiments on facial grooming did not show significant effects of OP on pain.

Changes in brain monoamine levels in neonatal rats exposed to bisphenol A at low doses

To examine whether exposure to bisphenol A (BPA) at low levels affect brain function, monoamine concentrations in hippocampus, striatum and brain stem, were investigated in neonatal male rats injected intracranially with BPA at 0-10microgkg(-1). Significant increases of serotonin (5-HT) in hippocampus, 5-HIAA and 5-HIAA/5-HT in brain stem, dopamine (DA) and DOPAC in striatum were observed at 28d after the injection on postnatal day 2. At 7d after the injection, increases in 5-HT and norepinephrine (NE) and decreases in DOPAC and 5-HIAA were observed in hippocampus. To investigate the degradation of BPA in brain, we also measured BPA concentrations of whole neonatal rat brain. Free BPA disappeared from brain tissues within 5h, even when the highest dose (1000microgkg(-1)) was injected. The present results suggest that BPA exposure at lower doses than environmentally relevant levels may have a great impact on monoamine levels in neonatal brain over 28d after its disappearance.

Validated spectrofluorimetric method for the determination of lamotrigine in tablets and human plasma through derivatization with o-phthalaldehyde

A sensitive, simple and selective spectrofluorimetric method was developed for the determination of Lamotrigine (LMT) in pharmaceutical formulations and biological fluids. The method is based on reaction of LMT with o-phthalaldehyde in presence of 2-mercaptoethanol in borate buffer of pH 9.8 to yield a highly fluorescent derivative that is measured at 448 nm after excitation at 337 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence-concentration plot was rectilinear over the range of 0.1-1.0 microg ml(-1) with lower limit of detection (LOD) 0.02 microg ml(-1) and limit of quantification (LOQ) 0.06 microg ml(-1) respectively. The proposed method was successfully applied to the the analysis of commercial tablets. Statistical comparison of the results obtained by the proposed and reference method revealed no significant difference in the performance of the two methods regarding the accuracy and precision respectively. The proposed method was further extended to the in-vitro and in-vivo determination of the drug in spiked and real human plasma. The mean percentage recoveries in spiked and real human plasma (n = 3) were 95.78 +/- 1.37 and 90.93 +/- 2.34 respectively. Interference arising from co-administered drugs was also studied. A proposal for the reaction pathway with o-phthalaldehyde was postulated.

Perinatal exposure to bisphenol a alters early adipogenesis in the rat

BACKGROUND

The causes of the current obesity pandemic have not been fully elucidated. Implication of environmental endocrine disruptors such as bisphenol A (BPA) on adipose tissue development has been poorly investigated.

OBJECTIVES

The aim of the present study was to evaluate the effects of perinatal exposure to BPA on early adipose storage at weaning.

METHODS

Pregnant Sprague-Dawley rats had access to drinking water containing 1 mg/L BPA from day 6 of gestation through the end of lactation. Pups were weaned on postnatal day (PND) 21. At that time, we investigated perigonadal adipose tissue of pups (weight, histology, gene expression). For the remaining animals, we recorded body weight and food intake for animals on either standard chow or a high-fat diet.

RESULTS

Gestational exposure to BPA did not alter the sex ratio or litter size at birth. On PND1, the weight of male and female BPA-exposed pups was increased. On PND21, body weight was increased only in females, in which parametrial white adipose tissue (pWAT) weight was increased about 3-fold. This excess of pWAT was associated with adipocyte hypertrophy and overexpression of lipogenic genes such as C/EBP-alpha (CAAT enhancer binding protein alpha), PPAR-gamma (peroxisome proliferator-activated receptor gamma), SREBP-1C (sterol regulatory element binding protein-1C), LPL (lipoprotein lipase), FAS (fatty acid synthase), and SCD-1 (stearoyl-CoA desaturase 1). In addition, gene expression of SREBP-1C, FAS, and ACC (acetyl-CoA carboxylase) was also increased in liver from BPA-exposed females at PND21, without a change in circulating lipids and glucose. After weaning, perinatal BPA exposure predisposed to overweight in a sex- and diet-dependent manner. We observed no change in food intake due to perinatal BPA exposure in rats on either standard chow or a high-fat diet.

CONCLUSIONS

Perinatal exposure to a low dose of BPA increased adipogenesis in females at weaning. Adult body weight may be programmed during early life, leading to changes dependent on the sex and the nutritional status. Although further studies are required to understand the mechanisms of BPA action in early life, these results are particularly important with regard to the increasing prevalence of childhood obesity and the context-dependent action of endocrine disruptors.

Bisphenol A levels in blood depend on age and exposure

We present two approaches to estimate blood concentrations of Bisphenol A (BPA). Simple kinetic principles were applied to calculate steady state plasma concentrations. A physiologically based model was used to simulate the blood concentration time profile in several age groups exploring the influence of not yet fully developed metabolic capacity on the blood concentrations in the newborn. Both approaches gave concordant results and are in excellent agreement with experimental results [Völkel, W., Colnot, T., Csanady, G.A., Filser, J.G., Dekant, W., 2002. Metabolism and kinetics of bisphenol A in humans at low doses following oral administration. Chem. Res. Toxicol. 15, 1281-1287]. The predictions also agree with published results obtained with a different physiologically based model. According to model simulations, BPA is present in the blood of the normal population at concentrations several orders of magnitude lower than most measurements reported in the literature. At the same external exposure level, the newborn is predicted to have 3 times greater blood concentration than the adult. This is due to the not yet fully developed glucuronidation activity in the newborn, not fully compensated by the unimpaired sulfation pathway. For the highest measured external BPA exposure, the predicted blood concentrations of 2.6 pg/ml (steady state concentration) and 8.2 pg/ml (peak concentration) in the adult are lower than the in vitro concentrations at which inhibiting adiponectin release from human adipocytes and stimulation of beta-cell production and secretion were observed.

Potencies of bisphenol A on the neuronal differentiation and hippocampal neurogenesis

Endocrine-disrupting chemicals (EDC) produce adverse effects on reproductive and immune function or neurological behavior, and may also induce cancer. The environmental EDC bisphenol A (BPA) is widely used in the manufacture of plastics and epoxy resins. BPA affects reproductive organ growth and development, but the potential adverse effects of BPA on neuronal development are not fully understood. Here, BPA concentration-dependently decreased proliferation of murine-derived multipotent neural progenitor cells (NPC), and high concentrations produced cytotoxicity. In contrast, low concentrations of BPA, which possess estrogenic activity, stimulated NPC differentiation into a neuronal phenotype. BPA treatment did not affect neonatal brain development in F1 mice. However, BPA treatment (20 mg/kg) accelerated formation of the dentate gyrus in postnatal day 1 mice. Prenatal and postnatal BPA treatment did not affect adult hippocampal neurogenesis in the dentate gyrus in 8-wk-old mice. Data indicate that BPA stimulates neuronal differentiation and might disrupt neonatal brain development.

Effects of estrogens on proliferation and differentiation of neural stem/progenitor cells

We investigated the effect of the female hormone 17beta-estradiol (E2) and the hormone mimic bisphenol A (BPA) on the proliferation and differentiation of rat neural stem/progenitors cells (NS/PCs) cultured from the telencephalon of embryonic day-15 rats. Basic fibroblast growth factor (FGF-2) is a potent mitogen of early generated NS/PCs, and is used for the proliferation of NS/PCs in vitro. Administration of E2 or BPA alone to the NS/PCs stimulated their proliferation in the absence but not in the presence of FGF-2. E2- or BPA-treatment increased the ratio of the oligodendrocytes generated from the NS/PCs to total cells; however, this ratio did not change when the cells were stimulated with platelet-derived growth factor (PDGF), a mitogen for oligodendrocyte precursors, or with neurotrophin-3, an oligogenic factor for glial progenitor cells. These results suggest that estrogens would influence the fate of NS/PCs when the cells are poorly supplied with mitogens or differentiation factors during the early stages of neurogenesis.

The effect of vitamin C on bisphenol A, nonylphenol and octylphenol induced brain damages of male rats

Bisphenol A (BPA), nonylphenol (NP) and octylphenol (OP) are endocrine-disrupting chemicals that has been shown to exert both toxic and estrogenic effects on mammalian cells. The aim of this study was to investigate if BPA, NP and OP induce oxidative stress on the brain tissue of male rats and if co-administration of vitamin C, an antioxidant, can prevent any possible oxidative stress. The male rats were divided into seven groups as control (vehicle), BPA, NP, OP, BPA+C, NP+C, OP+C. BPA, OP and NP (25 mg/(kg day)) were administrated orally to male Wistar rats for 45 days. In vitamin C co-administration groups (BPA+C, NP+C, OP+C), vitamin C (60 mg/(kg day)) were administrated orally along with BPA, OP and NP (25 mg/(kg day)) treatments. The rats in the control group received olive oil orally. The final body and absolute organ weights of treated rats did not show any significant difference when compared with the control group. Also, there were no significant difference in relative organ weights of BPA, NP, OP, BPA+C and NP+C groups when compared with control group. Only, relative organ weights were increased significantly in OP+C group compared with control group. Decreased levels of reduced glutathione (GSH) were found in the brains of BPA, NP, OP treated rats. The end product of lipid peroxidation, malondialdehyde (MDA), appeared at significantly higher concentrations in the BPA, NP, and OP treated groups when compared to the control group. On the other hand, there were no changes in the brain MDA and GSH levels of BPA+C, NP+C and OP+C groups compared with BPA, NP and OP treatment groups, respectively. In histopathologic examination, the vitamin C co-administrated groups had much more hyperchromatic cells in the brain cortex than that observed in the groups treated with only BPA, NP, and OP. The results of this study demonstrate that BPA, NP and OP generate reactive oxygen species that caused oxidative damage in the brain of male rats. In addition, vitamin C co-administration along with BPA, NP, and OP aggravates this oxidative damage in the brain of rats.

Second-derivative Synchronous Fluorometric Method for the Simultaneous Determination of Cinnarizine and Domperidone in Pharmaceutical Preparations. Application to Biological Fluids

A rapid, simple and highly sensitive second derivative synchronous fluorometric method has been developed for the simultaneous analysis of binary mixture of cinnarizine (CN) and domperidone (DOM). The method is based upon measurement of the native fluorescence of these drugs at Deltalambda=80 nm in aqueous methanol (50% V/V). The different experimental parameters affecting the native fluorescence of the studied drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.1 to 1.3 microg mL(-1) and 0.1-3.0 microg mL(-1) for CN and DOM, respectively with lower detection limits of 0.017 and 5.77 x 10(-3) microg mL(-1) and quantification limits of 0.058 and 0.02 microg mL(-1) for CN and DOM. The proposed method was successfully applied for the determination of the studied compounds in synthetic mixtures and in commercial tablets. The results obtained were in good agreement with those obtained with reference methods. The high sensitivity attained by the synchronous fluorometric method allowed the determination of CN in real and spiked human plasma. The mean % recoveries in case of spiked human plasma (n=3) were 96.39+/-1.18 while that in real human plasma (n = 3) was 104.67+/-4.16.

A novel HPLC fluorescence method for the quantification of methylphenidate in human plasma

A number of analytical methods have been established to quantify methylphenidate (MPH). However, to date no HPLC methods are applicable to human pharmacokinetic studies without the use of mass spectrometry (MS) detection. We developed a sensitive and reliable HPLC-fluorescence method for the determination of MPH in human plasma using 4-(4,5-diphenyl-1H-imidazol-2-yl) benzoyl chloride (DIB-Cl) as the derivatizing agent. An established GC-MS method was adopted in this study as a comparator assay. MPH was derivatized using DIB-Cl, and separated isocratically on a C18 column using a HPLC system with fluorescence detection (lambda(ex)=330 nm, lambda(em)=460 nm). The lower limit of quantification was found to be 1 ng/mL. A linear calibration curve was obtained over the concentrations ranging from 1 ng/mL to 80 ng/mL (r=0.998). The relative standard deviations of intra-day and inter-day variations were <or=9.10% and <or=7.58%, respectively. The accuracy ranged between 92.59% and 103.06%. The method was successfully applied to the pharmacokinetic study of a subject who received a single oral dose (0.3 mg/kg) of immediate-release MPH and yielded consistent results with that of the GC-MS method. This method is the first HPLC assay with non-MS detection providing sufficient reliability and sensitivity for both pre-clinical and clinical studies of MPH.

Suppressive effects of bisphenol A on the proliferation of neural progenitor cells

Endocrine disruptors (EDs) exert adverse effects on reproductive and immune function or neurological behavior. Bisphenol A (BPA), one of the environmental EDs, is widely used in the manufacture of plastics and epoxy resins. Studies reported that BPA affects reproductive organ growth and development. However, the potential adverse effects of BPA on neuronal development have not been fully explored. In this study, the potent harmful effects of BPA were investigated on the murine-derived multipotent neural progenitor cells (NPCs). Pretreatment of BPA significantly decreased proliferation of NPCs in a concentration-dependent manner. Moreover, at a high concentration (> 400 microM), BPA was cytotoxic to NPCs. However, the low concentrations of BPA, previously shown to exert estrogenic actions, did not affect the proliferation of NPCs. BPA altered the activation of extracellular signal-regulated kinases and c-Jun-N-Kinases in a different manner without affecting activities of p38 kinases. It was also found that reactive oxygen species (ROS) were elevated in NPCs exposed to high concentrations of BPA, indicating oxidative stress-related cytotoxicity. These data show adverse effects of BPA on the nervous system and potentially on neonatal brain development.

Sensitive quantification of atomoxetine in human plasma by HPLC with fluorescence detection using 4-(4,5-diphenyl-1H-imidazole-2-yl) benzoyl chloride derivatization

The first HPLC-fluorescence method for the determination of atomoxetine in human plasma was developed and validated. Atomoxetine was derivatized with 4-(4,5-diphenyl-1H-imidazol-2-yl) benzoyl chloride (DIB-Cl) under mild conditions, and separated isocratically on a C18 column using a HPLC system with fluorescence detection (lambdaex: 318 nm, lambdaem: 448 nm). A linear calibration curve was obtained over the concentration range 1-1000 ng/mL (r=0.999). The limit of detection (S/N=3) was 0.3 ng/mL. The relative standard deviations of intra-day and inter-day variations were < or =8.30% and 7.47%, respectively. This method is rapid, sensitive, and suitable for both basic and clinical studies of atomoxetine.

Determination of donepezil hydrochloride in human and rat plasma, blood and brain microdialysates by HPLC with a short C30 column

A simple and sensitive HPLC method with fluorescence (FL) detection for determination of donepezil (DP) in plasma and microdialysate samples was developed. A rapid isocratic separation of DP could be achieved by a short C30 column using mobile phases of 25 mM citric acid/50 mM Na2HPO4 (pH 6.0)-CH3CN (73:27%, v/v) containing 3.5 mM sodium 1-octanesulfonate for plasma and H2O-CH3CN-CH3OH (80:17:3%, v/v/v) containing 0.01% acetic acid for microdialysate. The eluate was monitored at 390 nm with an excitation at 325 nm. The detection limits (S/N = 3) of DP for human plasma, rat plasma and rat brain or blood microdialysates were 0.2, 1.0 and 2.1 ng/ml, respectively. Reproducible results could be obtained by using (+/-)-2-[(1-benzyl-piperidine-4-yl)ethyl]-5,6-dimethoxyindan-1-one hydrochloride as an internal standard (IS). The method was successfully applied for monitoring of DP levels in rat plasma, blood and brain microdialysates and patient plasma.

Evaluation of Oral and Intravenous Route Pharmacokinetics, Plasma Protein Binding, and Uterine Tissue Dose Metrics of Bisphenol A: A Physiologically Based Pharmacokinetic Approach

Bisphenol A (BPA) is a weakly estrogenic monomer used in the production of polycarbonate plastic and epoxy resins, both of which are used in food contact and other applications. A physiologically based pharmacokinetic (PBPK) model of BPA pharmacokinetics in rats and humans was developed to provide a physiological context in which the processes controlling BPA pharmacokinetics (e.g., plasma protein binding, enterohepatic recirculation of the glucuronide [BPAG]) could be incorporated. A uterine tissue compartment was included to allow the correlation of simulated estrogen receptor (ER) binding of BPA with increases in uterine wet weight (UWW) in rats. Intravenous- and oral-route blood kinetics of BPA in rats and oral-route plasma and urinary elimination kinetics in humans were well described by the model. Simulations of rat oral-route BPAG pharmacokinetics were less exact, most likely the result of oversimplification of the GI tract compartment. Comparison of metabolic clearance rates derived from fitting rat i.v. and oral-route data implied that intestinal glucuronidation of BPA is significant. In rats, but not humans, terminal elimination rates were strongly influenced by enterohepatic recirculation. In the absence of BPA binding to plasma proteins, simulations showed high ER occupancy at doses without uterine effects. Restricting free BPA to the measured unbound amount demonstrated the importance of including plasma binding in BPA kinetic models: the modeled relationship between ER occupancy and UWW increases was consistent with expectations for a receptor-mediated response with low ER occupancy at doses with no response and increasing occupancy with larger increases in UWW.

Stimulation of catecholamine synthesis by environmental estrogenic pollutants

Environmental estrogenic pollutants are compounds that have been shown to have estrogenic effects on fetal development and reproductive systems. Less attention, however, has been paid to their influence on neuronal functions. We report here the effects of estrogenic pollutants on catecholamine synthesis in bovine adrenal medullary cells used as a model system of noradrenergic neurons. Treatment of cultured bovine adrenal medullary cells with p-nonylphenol and bisphenol A at 10 nM for 3 d stimulated [14C]catecholamine synthesis from [14C]tyrosine and tyrosine hydroxylase activity, an effect that was not inhibited by ICI 182,780, an antagonist of estrogen receptors. Significant effects of p-nonylphenol on [14C]catecholamine synthesis were observed at 0.1 nM, which is 45 times lower than that of the international regulatory standard (4.5 nM), and the maximum effects were around 10-100 nM. The concentrations (0.1-10 nM) used in the present study are similar to the range observed in rivers in the United States or Europe. On the other hand, short-term treatment of cells with 10 nM p-nonylphenol for 10 min also activated tyrosine hydroxylase, which was suppressed by U0126, an inhibitor of MAPK kinase. Furthermore, treatment of cells with p-nonylphenol for 5 min increased the phospho-p44/42MAPK in a concentration-dependent (1-1000 nM) manner, whereas p-nonylphenol (100 nm, 2 d) enhanced both levels of non-phospho- and phospho-p44/42MAPK. These findings suggest that short-term and long-term treatment of cells with estrogenic pollutants at environmental concentrations stimulates catecholamine synthesis and MAPK through an estrogen receptor-independent pathway.

Inhibition of the norepinephrine transporter function in cultured bovine adrenal medullary cells by bisphenol A

We report here the effects of an environmental estrogen, bisphenol A, on norepinephrine (NE) transporter function in cultured bovine adrenal medullary cells. The effects of bisphenol A were compared to those of 17beta-estradiol. Bisphenol A significantly inhibited [3H]NE uptake by the cells in a concentration-dependent manner (1-100 microM). Kinetic analysis revealed that bisphenol A, as well as 17beta-estradiol, noncompetitively inhibited [3H]NE uptake. Bisphenol A and 17beta-estradiol inhibited the specific binding of [3H]desipramine to plasma membranes isolated from bovine adrenal medulla. As shown by Scatchard analysis of [3H]desipramine binding, bisphenol A increased the dissociation constant (K(d)) and decreased the maximal binding (B(max)), indicating a mixed type of inhibition. 17beta-Estradiol increased the K(d) without altering the B(max), thereby indicating competitive inhibition. The present findings suggest that bisphenol A inhibits the function of the NE transporter by acting on a site different from that of 17beta-estradiol in the adrenal medulla and probably in the brain noradrenergic neurons.

Lophine derivatives as versatile analytical tools

Lophine (2,4,5-triphenylimidazole) derivatives as versatile analytical tools in biomedical sciences are described. Chemiluminescence (CL) and fluorescence (FL) properties of the lophine derivatives are first demonstrated including the CL reaction mechanism, effects of substituents on CL yields, FL spectral behaviors, etc. Next, analytical applications to the determination of metal ions such as cobalt (II) and chromium (VI) are discussed. Finally, the application studies of lophine derivatives as CL and FL reagents for the determination of organic substances in biological materials are presented. Among the derivatives, 2-(4-hydrazinocarbonylphenyl)-4,5-diphenylimidazole (HCPI) and 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) are studied, with their excellent properties as labeling reagents for fatty acids and amines and/or phenols, respectively, in high-performance liquid chromatography. The utility of boronic acid derivatives as CL enhancers is also discussed in this review.

Measurement of bisphenol A levels in human blood serum and ascitic fluid by HPLC using a fluorescent labeling reagent

A sensitive column-switching HPLC method with fluorescence detection was developed for the determination of bisphenol A (BPA) in human blood serum and ascitic fluid samples. 4-(4,5-Diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) was used as the fluorescent label, and the excess reagent was removed by a column-switching technique. Liquid-liquid extraction with chloroform was used for the pretreatment of serum and ascitic fluid samples. BPA in both the samples could be determined in the concentration range of 0.1-7.0 ppb with the detection limit of 0.04 ppb at a signal-to-noise ratio of 3. The recoveries of BPA spiked to serum and ascitic fluid were 78.6 and 77.7%, respectively. The mean concentrations of BPA (n=9) in maternal and umbilical cord blood sera obtained from healthy pregnant women were 0.46+/-0.20 and 0.62+/-0.13 ppb, respectively. BPA levels (n=21) in blood sera and ascitic fluid obtained from the patients with sterility were also determined to be 0.46+/-0.20 and 0.56+/-0.19 ppb, respectively. Relationships of BPA concentrations were observed between maternal and umbilical cord blood serum samples (r=0.626), as well as blood serum and ascitic fluid samples (r=0.785).

Recent progress in derivatization methods for LC and CE analysis

The derivatization procedure with a suitable fluorescence or chemiluminescence reagent is performed for the purpose of increasing the detection sensitivity and selectivity, in high-performance liquid chromatography (HPLC) and/or capillary electrophoresis (CE). In this article, recent derivatization methods and their applications to biosamples are described. In HPLC, femto mol order of mass detection limits are obtained by derivatization. Regarding the fluorescence reagents, the use of water-soluble reagents has been effective to avoid an undesired adsorption in the process of determination of peptides. In CE, the advantages of having extremely low mass detection limits (ranging from atto to yocto mol level) and requiring only a very short analysis time (less than a few minutes) are made possible by using laser-induced fluorescence or near infra-red detections.