Trace analysis of contraceptive drug levonorgestrel in wastewater samples by a newly developed indirect competitive enzyme-linked immunosorbent assay (ELISA) coupled with solid phase extraction

The behavior of pharmaceutically active compounds and contrast agents during wastewater treatment - Combining sampling strategies and analytical techniques: A critical review

Increasing consumption of pharmaceuticals and the respective consequences for the aquatic environment have been the focus of many studies over the last thirty years. Various aspects in this field were investigated, considering diverse pharmaceutical groups and employing a wide range of research methodologies. Various questions from the perspectives of different research areas were devised and answered, resulting in a large mix of individual findings and conclusions. Collectively, the results of the studies offer a comprehensive overview. The large variety of methods and strategies, however, demands close attention when comparing and combining information from heterogeneous projects. This review critically examines the application of diverse sampling techniques as well as analytical methods in investigations concerning the behavior of pharmaceutically active compounds (PhACs) and contrast agents (CAs) in wastewater treatment plants (WWTPs). The combination of sampling and analysis is discussed with regard to its suitability for specific scientific problems. Different research focuses need different methods and answer different questions. An overview of studies dealing with the fate and degradation of PhACs and CAs in WWTPs is presented, discussing their strategic approaches and findings. This review includes surveys of anticancer drugs, antibiotics, analgesics and anti-inflammatory drugs, antidiabetics, beta blockers, hormonal contraceptives, lipid lowering agents, antidepressants as well as contrast agents for X-ray and magnetic resonance imaging.

A Highly Sensitive and Group-Specific Enzyme-Linked Immunosorbent Assay (ELISA) for the Detection of AFB1 in Agriculture and Aquiculture Products

Aflatoxins (AFs) including AFB1, AFB2, AFG1 and AFG2 are widely found in agriculture products, and AFB1 is considered one of the most toxic and harmful mycotoxins. Herein, a highly sensitive (at the pg mL-1 level) and group-specific enzyme-linked immunosorbent assay (ELISA) for the detection of AFB1 in agricultural and aquiculture products was developed. The AFB1 derivative containing a carboxylic group was synthesized and covalently linked to bovine serum albumin (BSA). The AFB1-BSA conjugate was used as an immunogen to immunize mice. A high-quality monoclonal antibody (mAb) against AFB1 was produced by hybridoma technology, and the mAb-based ELISA for AFB1 was established. IC50 and limit of detection (LOD) of the ELISA for AFB1 were 90 pg mL-1 and 18 pg mL-1, respectively. The cross-reactivities (CRs) of the assay with AFB2, AFG1, and AFG2 were 23.6%, 42.5%, and 1.9%, respectively, revealing some degree of group specificity. Corn flour, wheat flour, and crab roe samples spiked with different contents of AFB1 were subjected to ELISA procedures. The recoveries and relative standard deviation (RSD) of the ELISA for AFB1 in spiked samples were 78.3-116.6% and 1.49-13.21% (n = 3), respectively. Wheat flour samples spiked with the mixed AF (AFB1, AFB2, AFG1, AFG2) standard solution were measured by ELISA and LC-MS/MS simultaneously. It was demonstrated that the proposed ELISA can be used as a screening method for evaluation of AFs (AFB1, AFB2, AFG1, AFG2) in wheat flour samples.

A sensitive monoclonal antibody-based ELISA integrated with immunoaffinity column extraction for the detection of zearalenone in food and feed samples

Zearalenone (ZEN) is one of the most toxic mycotoxins widely found in agricultural products. In this study, a sensitive enzyme-linked immunosorbent assay (ELISA) integrated with immunoaffinity column extraction for the detection of ZEN in food and feed samples was developed. A ZEN derivative containing a carboxylic group was first synthesized and then linked to bovine serum albumin (BSA). The formed ZEN-BSA conjugate was used as the immunogen for the production of the monoclonal antibody (mAb) against ZEN. The hybridoma clones (1G5) capable of secreting antibodies against ZEN were successfully selected. Based on this mAb, the IC50 and LOD of the ELISA for ZEN were 0.37 ng mL-1 and 0.04 ng mL-1, respectively, which were 1.6-308.1 times lower than those in the published ELISAs, indicating the high sensitivity of our assay. There was no cross-reactivity of the mAb with other four mycotoxins (patulin, AFB1, DON, and OTA). Due to the high similarity in molecular structures among ZEN and its homologs (α-zearalanol, β-zearalanol, zearalanone, α-zearalenol, β-zearalenol), the CR values of the mAb with the homologs were within 3.59%-105.71%. Taking advantage of plenty of mAb, the immunoaffinity column was prepared by immobilizing the mAb on Sepharose-4B gel and filling it into an SPE column. ZEN spiked samples (corn, wheat, feed) were extracted using an immunoaffinity column and measured by ELISA and HPLC-FLD simultaneously. The recoveries of the ELISA for ZEN in the spiked samples were 92.46-105.48% with RSDs of 4.87-10.11%. A good correlation between ELISA (x) and HPLC-FLD (y) with the linear regression equation y = 1.0589x + 1.43815 (R2 = 0.998, n = 6) was obtained. To verify the applicability, the proposed ELISA was also applied to some real samples randomly collected from a local market. It was proven that the newly produced mAb-based ELISA was a feasible and sensitive method for the detection of ZEN in food and feed samples.

Progestogen-induced alterations and their ecological relevance in different embryonic and adult behaviours of an invertebrate model species, the great pond snail (Lymnaea stagnalis)

The presence of oral contraceptives (basically applying estrogens and/or progestogens) poses a challenge to animals living in aquatic ecosystems and reflects a rapidly growing concern worldwide. However, there is still a lack in knowledge about the behavioural effects induced by progestogens on the non-target species including molluscs. In the present study, environmental progestogen concentrations were summarised. Knowing this data, we exposed a well-established invertebrate model species, the great pond snail (Lymnaea stagnalis) to relevant equi-concentrations (1, 10, 100, and 500 ng L-1) of mixtures of four progestogens (progesterone, drospirenone, gestodene, levonorgestrel) for 21 days. Significant alterations were observed in the embryonic development time, heart rate, feeding, and gliding activities of the embryos as well as in the feeding and locomotion activity of the adult specimens. All of the mixtures accelerated the embryonic development time and the gliding activity. Furthermore, the 10, 100, and 500 ng L-1 mixtures increased the heart rate and feeding activity of the embryos. The 10, 100, and 500 ng L-1 mixtures affected the feeding activity as well as the 1, 10, and 100 ng L-1 mixtures influenced the locomotion of the adult specimens. The differences of these adult behaviours showed a biphasic response to the progestogen exposure; however, they changed approximately in the opposite way. In case of feeding activity, this dose-response phenomenon can be identified as a hormesis response. Based on the authors' best knowledge, this is the first study to investigate the non-reproductive effects of progestogens occurring also in the environment on molluscan species. Our findings contribute to the global understanding of the effects of human progestogens, as these potential disruptors can influence the behavioural activities of non-target aquatic species. Future research should aim to understand the potential mechanisms (e.g., receptors, signal pathways) of progestogens induced behavioural alterations.

Immunoassay-based approaches for development of screening of chlorpyrifos

Chlorpyrifos (CPF) is an extensively used organophosphate pesticide for crop protection. However, there are concerns of it contaminating the environment and human health with estimated three lakh deaths annually. Detection of CPF in blood samples holds significance to avoid severe health outcomes due to continuous exposure. The most common techniques for CPF detection are Gas chromatography (GC) and high-performance liquid chromatography (HPLC). However, these techniques might not be feasible at the community healthcare level due to high-cost instrumentation, time-consuming sample preparation protocol and skilled analysts. Therefore, rapid, effective and economical methods such as immunoassay would be imperative for CPF detection in biological samples. The vital step in immunoassay development is the design of a potent immunogen from non-immunogenic molecules. The molecular modelling protocol could assist in redesigning known CPF linkers and inserting them at different substitutable positions of CPF to get distinctive CPF derivatives. Molecular docking and binding free energy analysis can be used to identify the CPF derivatives having a better binding affinity with carrier protein compared to CPF. The top-ranked CPF derivatives based on docking score and binding energy could be ideal for synthesis and immunogen development. The present review will comprehend technological trends in immunoassay kits for detecting chlorpyrifos from biological samples.

Assessment of endocrine disruptor effects of levonorgestrel and its photoproducts: Environmental implications of released fractions after their photocatalytic removal

The presence of levonorgestrel (LNG) in water bodies via direct discharge and human excretion has been reported worldwide, but its effects on the reproduction of aquatic species and humans are still unknown. Owing to its recalcitrant properties, LNG is not completely removed during wastewater treatment plants, and many species may be exposed to low traces of this compound from discharged effluents. Thus, in this study, a photocatalytic process for removing LNG along with screening of endocrine disruptor effects for risk assessment was applied. Although the removal rate of LNG by ultraviolet C (UV-C) radiation was >90%, reproductive toxicity testing using the BeWo cell line exposed to LNG and its degraded fraction showed the reduced production of basal human chorionic gonadotropin hormone (β-hCG) by more than 73%, from 8.90 mIU mL^-1 to <2.39 mIU mL^-1, with both LNG and the degraded fraction. β-hCG hormone has been implicated in the viability of trophoblastic cells during the first trimester of pregnancy; therefore, degraded fractions and waterborne LNG may affect reproduction in some aquatic species and humans with low level of exposure.

Concentrations of levonorgestrel and ethinylestradiol in wastewater effluents: Is the progestin also cause for concern?

Synthetic hormones have been widely reported in treated sewage effluents, and consequently receiving aquatic environments. Ethinylestradiol (EE2) is a potent synthetic estrogen commonly used in conjunction with levonorgestrel in oral contraceptive pills. Both EE2 and levonorgestrel have been identified in the aquatic environment, but although there is a significant amount of literature on EE2, there is much less information on levonorgestrel. Using Australian prescription data as well as excretion and predicted wastewater removal rates, the concentrations of EE2 and levonorgestrel in Australian wastewater were calculated at 0.1 ng/L to 0.5 ng/L and 0.2 ng/L to 0.6 ng/L, respectively. Both compounds were analyzed in treated wastewater and surface water grab samples from 3 Southeast Queensland, Australia sites. The predicted no-effect concentration (PNEC) for EE2 of 0.1 ng/L was exceeded at most sites, with EE2 concentrations up to 2 ng/L in treated effluent, albeit quickly diluted to 0.1 ng/L to 0.2 ng/L in the receiving environment. A provisional PNEC for levonorgestrel of 0.1 ng/L derived in the present study was slightly lower than predicted effluent concentrations of 0.2 ng/L to 0.6 ng/L, indicating a potential risk of endocrine-related effects in exposed aquatic species. The detection limit for levonorgestrel in the present study was 2.5 ng/L, and all samples were below detection limit. The present study's results suggest that improvements in analytical capabilities for levonorgestrel are warranted to more accurately quantify the risk of this compound in the receiving environment. Environ Toxicol Chem 2016;35:1378-1385. © 2015 SETAC.

Plasmonic-ELISA: expanding horizons

Convergence of localized surface plasmon resonance of metal nanoparticles with classical ELISA has emerged as a new class of immunoassays, i.e. plasmonic ELISA, enabling biocatalysis mediated ultrasensitive naked-eye detection of disease biomarkers.

The challenge presented by progestins in ecotoxicological research: a critical review

Around 20 progestins (also called gestagens, progestogens, or progestagens) are used today in assisting a range of medical conditions from endometrial cancer to uterine bleeding and as an important component of oral contraception. These progestins can bind to a wide range of receptors including progestin, estrogen, androgen, glucocorticoid, and mineralocorticoid receptor, as well as sex hormone and corticosteroid binding globulins. It appears that only five of these (four synthetic and one natural) progestins have so far been studied in sewage effluent and surface waters. Analysis has reported values as either nondetects or low nanograms per liter in rivers. Seven of the progestins have been examined for their effects on aquatic vertebrates (fish and frogs). The greatest concern is associated with levonorgestrel, norethisterone, and gestodene and their ability to reduce egg production in fish at levels of 0.8-1.0 ng/L. The lack of environmental measurements, and some of the contradictions in existing values, however, hampers our ability to make a risk assessment. Only a few nanograms per liter of ethynodiol diacetate and desogestrel in water would be needed for fish to receive a human therapeutic dose for these progestins according to modeled bioconcentration factors. But for the other synthetic progestins levels would need to reach tens or hundreds of nanograms per liter to achieve a therapeutic dose. Nevertheless, the wide range of compounds, diverse receptor targets, and the effect on fish reproduction at sub-nanogram-per-liter levels should prompt further research. The ability to impair female reproduction at very low concentrations makes the progestins arguably the most important pharmaceutical group of concern after ethinylestradiol.

Effects of progesterone and norethindrone on female fathead minnow (Pimephales promelas) steroidogenesis

As knowledge of contaminants capable of adversely modulating endocrine functions increases, attention is focused on the effects of synthetic progestins as environmental endocrine disrupters. In the present study, effects of exposure to a synthetic progestin (norethindrone, 168 ± 7.5 ng/L) and endogenous progestogen (progesterone, 34 ± 4.1 ng/L) on steroidogenesis in adult female fathead minnows were examined. In vivo exposure to either compound lowered expression (nonsignificant) of luteinizing hormone (LHβ) levels in the brain along with significantly down-regulating the beta isoform of membrane progesterone receptor (mPRβ) in ovary tissue. The correspondence between lowered LHβ levels in the brain and mPRβ in the ovary is suggestive of a possible functional association as positive correlations between LHβ and mPR levels have been demonstrated in other fish species. In vitro exposure of ovary tissue to progesterone resulted in significantly elevated progestogen (pregnenolone, 17α-hydroxyprogesterone, and 17α,20β-dihydroxypregnenone) and androgen (testosterone) production. Whereas in vitro exposure to norethindrone did not significantly impact steroid hormone production but showed decreased testosterone production relative to solvent control (however this was not significant). Overall, this study showed that exposure to a natural progestogen (progesterone) and synthetic progestin (norethindrone), was capable of modulating LHβ (in brain) and mPRβ expression (in ovary).

A time-resolved fluorescence immunoassay for the ultrasensitive determination of diethylstilbestrol based on the double-codified gold nanoparticles

An ultrasensitive and selective method is presented for the determination of diethylstilbestrol (DES) using time-resolved fluorescence immunoassay (TRFIA) based on double-codified gold nanoparticles (DC-AuNPs). In this system, the DC-AuNPs, that are gold nanoparticles (AuNPs) modified with anti-DES antibody and SH-dsDNA-biotin, was regarded as signal amplifier. A competitive immunoreaction was performed on polystyrene microtitration plates, where the DES compete with the immobilized DES-ovalbumin on polystyrene microtitration plates to bind to anti-DES antibodies on DC-AuNPs, and the europium(III)-labeled streptavidin was added to link to the SH-dsDNA-biotin as a tracer. Fluorescence signal was amplified via the AuNPs and the biotin-streptavidin double amplification systems. Under the optimized condition, DES can be quantified by TRFIA. The linear range and the limit of detection of DES were 1.0×10(-6)-10ngmL(-1) and 0.4fgmL(-1), respectively. This method was applied to determine DES in beef sample, with the recoveries ranging from 88% to 105%.

The in vitro interference of synthetic progestogens with carp steroidogenic enzymes

Synthetic progestogens represent a class of pharmaceuticals widely used in oral contraceptives and in hormone replacement therapies. They reach the aquatic environment through wastewater effluents; however, environmental concentrations and effects on non-target organisms are poorly known. Given the important role of progestogens regulating fish spawning processes, this study aimed at assessing the in vitro interference of four currently used progestogens-drospirenone (DRO), levonorgestrel (LNG), norethindrone (NOR) and cyproterone acetate (CPA) - with key enzymatic activities involved in the synthesis of active steroids in carp (Cyprinus carpio). The enzymatic pathways investigated were (a) CYP17 (C17,20-lyase) and CYP11β involved in the synthesis of androgens, (b) CYP19 that catalyses the aromatization of androgens to estrogens, and (c) 20β-hydroxysteroid dehydrogenase (20β-HSD) responsible for the synthesis of maturation-inducing hormones. All tested progestogens significantly inhibited the synthesis of androgens: DRO (IC50: 3.8 μM) was the strongest inhibitor of CYP17 followed by CPA (IC50s: 183 μM). Moreover, NOR (IC50: 0.4 μM), DRO (IC50: 1.8 μM) and CPA (IC50s: 87 μM) inhibited CYP11β. An inhibition by NOR of ovarian CYP19 activity, and by DRO and CPA of 20β-HSD was also observed, but at rather high concentrations (500 μM). Overall, this study highlights the potential of synthetic progestogens, and particularly DRO and NOR, to interfere with the biosynthesis of androgens in carp gonads.

Phytoremediation of levonorgestrel in aquatic environment by hydrophytes

Adsorption and degradation of levonorgestrel (LNG) by two hydrophytes, Cyperus alternifolius (CA) and Eichhornia crassipes (EC), were investigated under light-shielding conditions in the water column. Variations of LNG concentrations in water, plant root epidermis, root, stem and leaf of the plants were analyzed. The results indicated that the removal efficiency of LNG by hydrophytes over the period of 50days was significantly greater than the blank control (p<0.05), with the removal rates of 79.80%±3.10% and 78.86%±2.55% for CA and EC, respectively. Compared with bio-adsorption, bio-conversion of LNG was found to be the dominant elimination pathway, evidenced by relatively high conversion rates (77.31%±2.68% for CA and 77.82%±2.95% for EC), while the adsorption rates were lower (1.77%±0.90% for CA and 1.05%±0.40% for EC). The bio-adsorption and conversion of LNG showed no significant differences between the two hydrophytes. Additionally, the mineralization on root epidermis played an important role in the reduction of LNG in water.

The synthetic progestin megestrol acetate adversely affects zebrafish reproduction

Synthetic progestins contaminate the aquatic ecosystem, and may cause adverse health effects on aquatic organisms. Megestrol acetate (MTA) is present in the aquatic environment, but its possible effects on fish reproduction are unknown. In the present study, we investigated the endocrine disruption and impact of MTA on fish reproduction. After a pre-exposure period of 14 days, reproductively mature zebrafish (Danio rerio) (F0) were exposed to MTA at environmental concentrations (33, 100, 333, and 666 ng/L) for 21 days. Egg production was decreased in F0 fish exposed to MTA, with a significant decrease at 666 ng/L. The exposure significantly decreased the circulating concentrations of estradiol (E2) and testosterone (T) in female fish or 11-keto testosterone (11-KT) in male fish. MTA exposure significantly downregulated the transcription of certain genes along the hypothalamic-pituitary-gonadal (HPG) axis. MTA did not affect early embryonic development or hatching success in the F1 generation. The present study showed that MTA is a potent endocrine disruptor in fish, and short-term exposure to MTA could significantly affect reproduction in fish and negatively impact the fish population.

Metabolic and reproductive effects of relatively low concentrations of beclomethasone dipropionate, a synthetic glucocorticoid, on fathead minnows

Pharmaceuticals present in the aquatic environment could adversely affect aquatic organisms. Synthetic glucocorticoids (GC) are used in large quantities as anti-inflammatory drugs and have been reported to be present in river water. In order to assess the impact of environmental concentrations of GCs, an in vivo experiment was conducted with adult fathead minnows. Fish were exposed to 0.1 μg/L, 1 μg/L, or 10 μg/L beclomethasone dipropionate (BCMD) via a flow-through system over a period of 21 days. Similar duplicate tanks served as control, with no chemical added. There was a concentration-related increase in plasma glucose concentration and a decrease in blood lymphocyte count. Induction of male secondary sexual characters and a decreasing trend in plasma vitellogenin (Vtg) concentrations in female fish were observed with increasing exposure concentration of BCMD. Expression profiles of selected genes (phosphoenolpyruvate carboxykinase - PEPCK, glucocorticoid receptor - GR, and Vtg) in liver also demonstrated concentration-related effects at all three tested concentrations. The results suggest that GCs could cause effects in lower micrograms per liter concentrations that could be environmentally relevant for total GCs present in the environment. Therefore, studies to determine the environmental concentrations of GCs and no effect concentrations are needed to assess if GCs pose a risk to the aquatic environment.

Progestins and antiprogestins affect gene expression in early development in zebrafish (Danio rerio) at environmental concentrations

Progesterone (P4) and synthetic progestins (gestagens) from contraceptives and hormone therapy occur in treated wastewater and surface water, and they may have adverse effects on aquatic organisms. Little is known about the molecular and reproductive effects of P4 and synthetic progestins in fish, and effects of the antiprogestin mifepristone (RU486, an abortive) are unknown. We aimed at elucidating effects on the hormone system by quantitative determination of transcriptional changes of target genes induced by 2, 20, and 200 ng/L P4, RU486, norethindrone (NET), and levonorgestrel (LNG). We exposed zebrafish embryos for 144 h post fertilization (hpf) to these compounds and analyzed expressional changes of ar, esr1, vtg1, hsd17ß3, and progesterone (pgr), mineralo- (mr), and glucocorticoid (gr) receptors, each at 48, 96, and 144 hpf. Concentrations of NET and LNG were constant during exposure, while P4 and RU486 decreased. P4 and RU486 were the most potent steroids. Significant up to 4-fold induction of pgr, ar, mr, and hsd17b3 occurred at 2 ng/L P4 and higher, while RU484 inhibited pgr expression. NET and LNG modulated some transcripts mainly above 2 ng/L. The expressional chances occurring at environmental levels may translate to negative interference with differentiation of brain and gonads, and consequently reproduction.

Occurrence, fate and removal of synthetic oral contraceptives (SOCs) in the natural environment: a review

Synthetic oral contraceptives (SOCs) are a group of compounds with progestagenic and/or androgenic activities, with some also possessing estrogenic activities. Recent research has documented that some of these emerging contaminants have adverse effects on aquatic organisms at very low concentrations. To facilitate the evaluation of their latent risks, published works on their occurrence and fate in the environment are reviewed. Androgenic/progestagenic relative potencies or relative binding affinity of these SOCs as well as their physicochemical properties and toxicity are summarized. Appropriate analytical methods are outlined for various environmental sample types, including methods of sample preparation and limit of detection/quantification (LOD/LOQ). Finally results on their occurrence and fate in wastewater treatment plants (WWTPs) and other environments are critically examined.

In vivo treatment with progestogens causes immunosuppression of carp Cyprinus carpio leucocytes by affecting nitric oxide production and arginase activity

In this study, carp Cyprinus carpio were injected with various steroid compounds, including synthetic and natural progestogens and the glucocorticoid cortisol, to investigate effects on leucocytes isolated from their kidneys. Injection of cortisol led to an increased spleeno-somatic index (I(S)) on day 21 post-injection (pi) and immunosuppressive effects measured as decreased nitric oxide (NO) production and increased arginase activity in isolated leucocytes on days 14 and 21 pi, respectively. Moreover, reduced NO production was also observed after injection of the synthetic progestogens, levonorgestrel (LEV) and medroxyprogesterone acetate. In addition, LEV influenced arginase activity in head kidney cells on day 14 and day 21 pi. This study is the first demonstration in fishes that the application of these steroid compounds in vivo affects NO production and arginase activity of isolated leucocytes.

Determination of diethylstilbestrol based on biotin-streptavidin-amplified time-resolved fluoro-immunoassay

A rapid and sensitive time-resolved fluoroimmunoassay (TR-FIA) based on the biotin-streptavidin amplification system was developed for the determination of diethylstilbestrol (DES). Europium-labelled streptavidin derivatives combined with europium and anhydride of diethylene triamine penta-acetic acid were used to label streptavidin; biotin was coupled with goat anti-rabbit IgG to form a biotin-goat anti-rabbit IgG bridge between streptavidin-europium and the anti-DES antibody in the immunoassay. The DES assay was carried out by measuring the fluorescence of Eu(3+) -SA at 615 nm. The presented method produced a wide linear range, 0.001-1000.0 ng/mL, and a detection limit up to 0.81 pg/mL for DES. The method was applied to determine DES in serum samples, with recoveries of 97.4-107.8% and RSD 1.32-4.04%. The assay results by the present method showed that biotin-streptavidin amplified TR-FIA for DES detection; it may offer high sensitivity and promising alternative special methods in biological samples.

Current approaches to trace analysis of pharmaceuticals and personal care products in the environment

A large number of xenobiotics including pharmaceuticals and personal care products are continuously released into the environment. Effluents from sewage treatment plants are well known to be the major source for introduction of pharmaceuticals and personal care products into the aquatic system. In recent years, reliable methods have been established for residue analysis of these pollutants down to low ng/L levels. In this review, the different approaches to their trace determination are reviewed with special attention being paid to sample preparation procedures, state-of-the-art high-performance separation methods hyphenated with mass spectrometry, and immunochemical methods.

A sensitive and specific enzyme-linked immunosorbent assay for the detection of lincomycin in food samples

BACKGROUND

Lincomycin (LIN) is an antibiotic widely used in veterinary medicine to cure infections caused by Gram-positive pathogens. Although the toxicity of LIN is not serious, it will cause adverse effects in humans, such as pseudomembranous enteritis and bacterial resistance. In this study, for the preparation of a LIN derivative, a novel modification method was adopted. The LIN derivative modified at 2-position with a carboxylic group at the end of the spacer was synthesised and coupled to carrier proteins. A LIN polyclonal antibody-based enzyme-linked immunosorbent assay (ELISA) was developed and characterised.

RESULTS

The ELISA standard curve was constructed with concentrations of 0.1-1000 ng mL(-1). The IC(50) value for nine standard curves was in the range 23.7-29.3 ng mL(-1) and the limit of detection at a signal-to-noise ratio of 3 was 0.15-0.98 ng mL(-1). The cross-reactivity value of the LIN antibody with clindamycin hydrochloride, a homologue of LIN with similar molecular structure, was 18.9%, while less than 0.1% cross-reactivity was found with seven other compounds. For LIN-spiked food samples, the recoveries and relative standard deviation (RSD) were 76.6-117.6% and 1.7-34.6%, respectively.

CONCLUSION

The proposed ELISA can be utilised as a sensitive and specific analytical tool for the detection of LIN in food samples.

Reproductive responses in fathead minnow and Japanese medaka following exposure to a synthetic progestin, Norethindrone

Synthetic progestins, such as Norethindrone (NET), are common ingredients in oral contraceptives and in treatment for post-menopausal problems. Given the widespread use of oral contraceptives and post-menopausal treatments, several reports have targeted and identified progestins in aquatic environments. In fish, progestins play an important role in the stimulation of oocyte final maturation and ovulation in females, stimulation of spermiation and sperm motility in males, and the initiation of meiosis in both sexes. They also have a role as pheromones in some species. Given the pivotal role that progestins play in reproduction, their appreciable daily dose (i.e. microg to mg range in contraceptives and hormone replacement therapies) and continuous use pattern, it is important to understand the potential risk these compounds pose once discharged into the aquatic environment. Since little published data are available on this class of compounds, our research focused on the reproductive effects of NET on the fathead minnow and Japanese medaka. A 28 day static-renewal reproduction study with Japanese medaka indicated that NET produces a significant decrease in fecundity at aqueous concentrations >or=25 ng/L. A 21 day flow-though fathead minnow reproduction study also demonstrated that NET causes a significant decrease in fecundity in the low ng/L range. Fathead minnow morphological changes (i.e. female fin spots) suggest that NET exposure may have a potent androgenic effect on fish; however, plasma 11-Ketotestosterone (11-KT) concentrations were reduced in males at the highest exposure concentration. Collectively, these data indicate that further investigation of reproductive responses associated with synthetic progestins is warranted.

The role of the maturation-inducing steroid, 17,20beta-dihydroxypregn-4-en-3-one, in male fishes: a review

The major progestin in teleosts is not progesterone, as in tetrapods, but 17,20beta-dihydroxypregn-4-en-3-one (17,20beta-P) or, in certain species, 17,20beta,21-trihydroxy-pregn-4-en-3-one (17,20beta,21-P). Several functions for 17,20beta-P and 17,20beta,21-P have been proposed (and in some cases proved). These include induction of oocyte final maturation and spermiation (milt production), enhancement of sperm motility (by alteration of the pH and fluidity of the seminal fluid) and acting as a pheromone in male cyprinids. Another important function, initiation of meiosis (the first step in both spermatogenesis and oogenesis), has only very recently been proposed. This is a process that takes place at puberty in all fishes and once a year in repeat spawners. The present review critically examines the evidence to support the proposed functions of 17,20beta-P in males, including listing of the evidence for the presence of 17,20beta-P in the blood plasma of male fishes and discussion of why, in many species, it appears to be absent (or present at low and, in some cases, unvarying concentrations); consideration of the evidence, obtained mainly from in vitro studies, for this steroid being predominantly produced by the testis, for its production being under the control of luteinizing hormone (gonadotrophin II) and, at least in salmonids, for two cell types (Leydig cells and sperm cells) being involved in its synthesis; discussion of the factors involved in the regulation of the switch from androgen to 17,20beta-P production that seems to occur in many species just at the time of spermiation; discussion of the effects of in vivo injection and application of 17,20beta-P (and closely related compounds) in males; a listing of previously published evidence that supports the proposed new function of 17,20beta-P as an initiator of meiosis; finally, discussion of the evidence for environmental endocrine disruption by progestins in fishes.

Progestogens cause immunosuppression of stimulated carp (Cyprinus carpio L.) leukocytes in vitro

The involvement of steroid hormones in direct and indirect regulation and modulation of immune responses is well recognized in mammals. Here, we demonstrate that progestogens are capable of influencing the innate immunity in fish as well. Therefore, we confirmed the known immunosuppressive effects of natural progesterone (P4), and compared them to influences of 17alpha,20beta-dihydroxy progesterone (DHP4) and the synthetic progestins, medroxyprogesterone acetate (MPA) and levonorgestrel (LEV), on NO release by in vitro-stimulated carp leukocytes derived from both, head and trunk kidney, respectively. DHP4 known as the main maturation-inducing steroid in many teleosts potently inhibited the NO release by carp leukocytes. The synthetic progestin MPA, which may also be environmentally relevant due to its world-wide use in hormonal contraception, significantly decreased NO formation by head and trunk kidney cells. In contrast, LEV showed no significant influence on NO release by head and trunk kidney leukocytes. The observed immunosuppressive actions of progestogens on NO production were compared to the known impairment by natural and synthetic glucocorticoids. Determining the potential impact of progestogens on mRNA expression of iNOS by means of semi-quantitative reverse transcription polymerase chain reactions (RT-PCR) revealed downregulation of proinflammatory type I immune response characteristics at high concentrations. These findings demonstrate for the first time that similar to the known effects of natural progesterone synthetic progestogens are also able to influence immune signaling cascades in fish, and provide evidence that these steroids are capable of influencing mRNA expression of iNOS. The induction of a regulatory type II immune response by progestogens is a striking example of interference of female steroid-mediated events with the piscine immune system. Furthermore, the identification of a partial sequence of a membrane-associated progestogen receptor (mPR) in carp leukocytes by RT-PCR indicates a specific mechanism underlying the observed effects of progestogens on these immune cells.