A high-performance liquid chromatography-electrospray-tandem mass spectrometry analysis of cortisol and metabolites in placental perfusate

Hydrogen sulfide measurement using sulfide dibimane: critical evaluation with electrospray ion trap mass spectrometry

Accurate measurement of hydrogen sulfide bioavailability remains a technical challenge due to numerous issues involving sample processing, detection methods used, and actual biochemical products measured. Our group and others have reported that reverse phase HPLC detection of sulfide dibimane (SDB) product from the reaction of H2S/HS(-) with monobromobimane allows for analytical detection of hydrogen sulfide bioavailability in free and other biochemical forms. However, it remains unclear whether possible interfering contaminants may contribute to HPLC SDB peak readings that may result in inaccurate measurements of bioavailable sulfide. In this study, we critically compared hydrogen sulfide dependent SDB detection using reverse phase HPLC (RP-HPLC) versus quantitative SRM electrospray ionization mass spectrometry (ESI/MS) to obtain greater clarity into the validity of the reverse phase HPLC method for analytical measurement of hydrogen sulfide. Using an LCQ-Deca ion-trap mass spectrometer, SDB was identified by ESI/MS positive ion mode, and quantified by selected reaction monitoring (SRM) using hydrocortisone as an internal standard. Collision induced dissociation (CID) parameters were optimized at MS2 level for SDB and hydrocortisone. ESI/MS detection of SDB standard was found to be a log order more sensitive than RP-HPLC with a lower limit of 0.25 nM. Direct comparison of tissue and plasma SDB levels using RP-HPLC and ESI/MS methods revealed comparable sulfide levels in plasma, aorta, heart, lung and brain. Together, these data confirm the use of SDB as valid indicator of H2S bioavailability and highlights differences between analytical detection methods.

Neuroactive steroids in pregnancy: key regulatory and protective roles in the foetal brain

Neuroactive steroid concentrations are remarkably high in the foetal brain during late gestation. These concentrations are maintained by placental progesterone synthesis and the interaction of enzymes in the placenta and foetal brain. 5α-Pregnane-3α-ol-20-one (allopregnanolone) is a key neuroactive steroid during foetal life, although other 3α-hydroxy-pregnanes may make an additional contribution to neuroactive steroid action. Allopregnanolone modulates GABAergic inhibition to maintain a suppressive action on the foetal brain during late gestation. This action suppresses foetal behaviour and maintains the appropriate balance of foetal sleep-like behaviours, which in turn are important to normal neurodevelopment. Neuroactive steroid-induced suppression of excitability has a key role in protecting the foetal brain from acute hypoxia/ischaemia insults. Hypoxia-induced brain injury is markedly increased if neuroactive steroid levels are suppressed and there is increased seizure activity. There is also a rapid increase in allopregnanolone synthesis and hence levels in response to acute stress that acts as an endogenous protective mechanism. Allopregnanolone has a trophic role in regulating development, maintaining normal levels of apoptosis and increasing myelination during late gestation in the brain. In contrast, chronic foetal stressors, including intrauterine growth restriction, do not increase neuroactive steroid levels in the brain and exposure to repeated synthetic corticosteroids reduce neuroactive steroid levels. The reduced availability of neuroactive steroids may contribute to the adverse effects of chronic stressors on the foetal and newborn brain. Preterm birth also deprives the foetus of neuroactive steroid mediated protection and may increase vulnerability to brain injury and suboptimal development. These finding suggest replacement therapies should be explored. This article is part of a Special Issue entitled 'Pregnancy and steroids'.

Determination of cortisol production rates with contemporary liquid chromatography-mass spectrometry to measure cortisol-d(3) dilution after infusion of deuterated tracer

OBJECTIVES

Measurement of 24-h cortisol production rate (CPR) using steady-state infusion of deuterated cortisol and analysis of stable-isotope dilution by MS is a valuable tool to examine hypothalamic-pituitary-adrenal axis activity in humans. We have developed and validated an improved method for measuring cortisol dilution with contemporary LC-MS technology.

DESIGN AND METHODS

Plasma samples and calibrators were extracted with ethylacetate. LC-MS was performed with a Surveyor HPLC and TSQ Quantum triple-quadrupole mass spectrometer equipped with an atmospheric pressure chemical ionization (APCI) source.

RESULTS

Selectivity was improved over previous methods via elimination of an interferent identified as 20β-dihydrocortisol. The LLOQ for cortisol-d(3) was 2.73nmol/L and LOD 1.37nmol/L. Plasma calibrators were linear over the concentration range 1.5-10% cortisol-d(3), with correlation coefficients >0.995.

CONCLUSIONS

This APCI LC-MS method offers simplified sample work-up and analysis and enables selective detection of the low concentration of cortisol-d(3) infused for determination of 24-h CPR.

Quantitative measurements of corticosteroids in ex vivo samples using on-line SPE-LC/MS/MS

Abnormal elevation of 11beta-HSD1 activities in tissues, such as fat and brain, may contribute to the development of the abdominal obesity and Alzheimer disease, and the inhibition of 11beta-HSD1 might be beneficial to the management of these diseases. To assess the effects of pharmacologic inhibitors of 11beta-HSD1, we developed a fast LC/MS/MS method to quantify corticosteroids in minced tissue samples in the presence of 11beta-HSD substrates. The novel on-line SPE-LC/MS/MS method was developed with dual binary gradient and a throughput of 4.5 min/sample. A total of six corticosteroids (cortisol, cortisone, corticosterone, dehydrocorticosterone, dexamethasone, and dehydrodexamethasone) were studied. The lower limit of quantitation from 0.40 to 11.4 fmol and 4.5 orders magnitude of dynamic range were obtained for these six compounds. Three novel enzymatic bi-products, all isomers of cortisol, were observed in the liver or fat samples. Two of them were identified by matching the HPLC retention times and MS/MS spectra with authentic compounds. The potential interferences of these isomers and their removal are discussed.

Determination of free tetrahydrocortisol and tetrahydrocortisone ratio in urine by liquid chromatography-tandem mass spectrometry

OBJECTIVE

Measurement of urinary free tetrahydrocortisol and tetrahydrocortisone ratio (allo-THF+THF)/THE is clinically important in the diagnosis of hypertension caused by congenital absence of 11beta-hydroxysteroid dehydrogenase type 2 (apparent mineralocorticoid excess, AME) or inhibition of the enzyme after licorice ingestion. Although gas chromatography-mass spectrometry (GC-MS) provides reliable results, it requires derivatization and is lengthy and time-consuming. The purpose of this study was to demonstrate that detection by liquid chromatography-mass spectrometry (LC-MS) is a potentially superior method.

MATERIAL AND METHODS

The analysis utilizes 1 mL urine. The samples were extracted with solid-phase extraction (SPE) using ethyl acetate as eluent. The extract was evaporated to dryness, and allo-tetrahydrocortisol (allo-THF), THF and THE concentrations were analyzed by LC-MS/MS operating in the negative mode after separation on a reversed-phase column. The calibration curves exhibited consistent linearity and reproducibility in the range of 7.5-120 nmol/L. Interassay CVs were 7.0-10 % at mean ratios of (allo-THF+THF)/THE of 0.54-1.9. The detection limit of the analytes was 0.4-0.8 nmol/L (signal-to-noise ratio = 3). The mean recovery of the three analytes ranged from 88 to 95 %. The regression equation for the free ratio using the LC-MS/MS (x) method and the total ratio using the GC-MS (y) method was: y = 0.30x+0.91 (r = 0.61; n = 25).

CONCLUSIONS

The sensitivity and specificity of the LC-MS/MS method offer an advantage over GC-MS by eliminating derivatization. The high costs of equipment are balanced by higher through-put, owing also to shorter chromatographic run times.

Cell-based assay for screening 11beta-hydroxysteroid dehydrogenase inhibitors using liquid chromatography/tandem mass spectrometry detection

Cortisol is an important glucocorticoid that regulates many physiological pathways by activating various intracellular receptors. The type 1 isozyme of 11beta-hydroxysteroid dehydrogenase (11beta-HSD1) functions in vivo predominantly as a reductase by converting cortisone into cortisol. A high-throughput liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed to screen for inhibitors of 11beta-HSD1 by monitoring cortisol and cortisone simultaneously. The injection cycle time can be as fast as 1 min/sample, making it amenable to the analysis of large numbers of the cell-assay samples in the screening of 11beta-HSD inhibitors. The reductase and dehydrogenase activities of 11beta-HSD1 are assessed separately.

Determination of corticosteroids in tissue samples by liquid chromatography-tandem mass spectrometry

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of corticosterone and 11-dehydrocorticosterone (11-DHC) levels in KKA(y) mouse liver and adipose tissue, and hydrocortisone and cortisone levels in human adipose tissue has been developed. The corticosteroids were extracted from liver tissue with methanol/water and ethyl acetate for adipose tissue samples. Corticosterone and 11-DHC were separated with a methanol gradient and hydrocortisone and cortisone with an acetonitrile gradient containing trifluoroacetic acid on a reversed-phase column within 15 min. The corticosteroids were detected after electrospray ionization in positive mode with multiple reaction monitoring (MRM). The limits of quantification (LOQ) were estimated to be 15 nmol/kg liver and 1.6 nmol/kg adipose tissue for corticosterone and 5.4 nmol/kg liver and 0.92 nmol/kg adipose tissue for 11-DHC. The LOQ was estimated to be 0.2 nmol/kg adipose tissue for hydrocortisone and 0.4 nmol/kg adipose tissue for cortisone. The limits of detection (LOD) at 3 times S/N were estimated to be 0.07 nmol/kg adipose tissue for hydrocortisone 0.1 nmol/kg adipose tissue for cortisone. The variation of endogenous levels in KKA(y) mouse from different animals (CV%) was high with mean liver tissue levels of 117+/-25 (S.D.)nmol/kg for corticosterone and 62+/-19 (S.D.)nmol/kg for 11-DHC (n=5) and adipose tissue levels of 39+/-20 (S.D.)nmol/kg for corticosterone and 2.4+/-0.9 (S.D.)nmol/kg for 11-DHC (n=9). Endogenous levels in human biopsy samples from adipose tissue were 12+/-7.0 (S.D.)nmol/kg for hydrocortisone and 3.0+/-1.6 (S.D.)nmol/kg for cortisone (n=16). The new LC-MS/MS methods showed sufficient sensitivity and selectivity for determination of endogenous levels of corticosteroids in both KKA(y) mouse liver and adipose tissue samples and human adipose tissue samples. The selectivity of the methods was verified by analysis of two different productions from each analyte.

Human hair follicles display a functional equivalent of the hypothalamic-pituitary-adrenal axis and synthesize cortisol

The skin and its major appendages are prominent target organs and potent sources of key players along the classical hypothalamic-pituitary axis, such as corticotropin releasing hormone (CRH), adrenocorticotropic hormone (ACTH), and alpha melanocyte stimulating hormone (alpha-MSH), and even express key steroidogenic enzymes. Therefore, it may have established local stress response systems that resemble the hypothalamic-pituitary-adrenal (HPA) axis. However, functional evidence that this is indeed the case in normal human skin in situ has still been missing. We show that microdissected, organ-cultured human scalp hair follicles respond to CRH stimulation by up-regulating proopiomelanocortin (POMC) transcription and immunoreactivity (IR) for ACTH and alpha-MSH, which must have been processed from POMC. CRH, alpha-MSH, and ACTH also modulate expression of their cognate receptors (CRH-R1, MC1-R, MC2-R). In addition, the strongest stimulus for adrenal cortisol production, ACTH, also up-regulates cortisol-IR in the hair follicles. Isolated human hair follicles secrete substantial levels of cortisol into the culture medium, and this activity is further up-regulated by CRH. CRH also modulates important functional hair growth parameters in vitro (hair shaft elongation, catagen induction, hair keratinocyte proliferation, melanin production). Finally, human hair follicles display HPA axis-like regulatory feedback systems, since the glucocorticoid receptor agonist hydrocortisone down-regulates follicular CRH expression. Thus, even in the absence of endocrine, neural, or vascular systemic connections, normal human scalp hair follicles directly respond to CRH stimulation in a strikingly similar manner to what is seen in the classical HPA axis, including synthesis and secretion of cortisol and activation of prototypic neuroendocrine feedback loops.

Simultaneous analysis of twenty-one glucocorticoids in equine plasma by liquid chromatography/tandem mass spectrometry

A method for the simultaneous separation, identification, quantification and confirmation of the presence of 21 glucocorticoids (GCC) in equine plasma by liquid chromatography coupled with triple stage quadrupole tandem mass spectrometry (LC/TSQ-MS/MS) is described. Plasma sample augmented with the 21 GCC was extracted with methyl tert-butyl ether (MTBE) and analyzed by positive electrospray ionization. Desoxymetasone or dichlorisone acetate was used as the internal standard (IS). Quantification was performed by IS calibration. For each drug, one major product ion was chosen and used for screening for that drug. Analyte confirmation was performed by using the three most intense product ions formed from the precursor ion and the corresponding mass ratios. The recovery of the 21 GCC when spiked into blank plasma at 5 ng/mL was 45-200% with coefficient of variation (CV) from 0.3-18%. The limit of detection (LOD) and that of quantification (LOQ) for most of the analytes were 50-100 pg/mL and 1 ng/mL, respectively, whereas that of confirmation (LOC) was 100-300 pg/mL depending on the analyte. Intra- and inter-day precisions expressed as CV for quantification of 1 and 10 ng/mL was 1.0-17%, and 0.51-19%, respectively, and the accuracy was from 84-110%. The linear concentration range for quantification was 0.1-100 ng/mL (r(2) > 0.997). Estimated measurement uncertainty was from 11-37%. This study was undertaken to develop a method for simultaneous screening, identification, quantification and confirmation of these agents in post-race equine plasma samples. The method has been successfully applied to screening of a large number of plasma samples obtained from racehorses in competition and in pharmacokinetic studies of dexamethasone in the horse and concurrent changes in endogenous GCC, hydrocortisone and cortisone. The method is simple, sensitive, selective and reliably reproducible.

Development and Evaluation of a Candidate Reference Method for the Determination of Total Cortisol in Human Serum Using Isotope Dilution Liquid Chromatography/Mass Spectrometry and Liquid Chromatography/Tandem Mass Spectrometry

Cortisol is an important diagnostic marker for the production of steroid hormones, and accurate measurements of serum cortisol are necessary for proper diagnosis of adrenal function. A candidate reference method involving isotope dilution coupled with liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) has been developed and critically evaluated. An isotopically labeled internal standard, cortisol-d(3), was added to serum, followed by equilibration and solid-phase and ethyl acetate extractions to prepare samples for liquid chromatography/mass spectrometry electrospray ionization (LC/MS-ESI) and liquid chromatography/tandem mass spectrometry electrospray ionization (LC/MS/MS-ESI) analyses. (M + H)(+) ions at m/z 363 and 366 for cortisol and its labeled internal standard were monitored for LC/MS. The transitions of (M + H)(+) --> [(M + H)(+) - 2H(2)O] at m/z 363 --> 327 and 366 --> 330 were monitored for LC/MS/MS. The accuracy of the measurement was evaluated by a comparison of results of this candidate reference method on lyophilized human serum reference materials for cortisol [Certified Reference Materials 192 and 193] with the certified values determined by gas chromatography/mass spectrometry reference methods and by a recovery study for the added cortisol. The results of this method for total cortisol agreed with the certified values within 1.1%. The recovery of the added cortisol ranged from 99.8% to 101.0%. This method was applied to the determination of cortisol in samples of frozen serum pools. Excellent precision was obtained with within-set CVs of 0.3%-1.5% and between-set CVs of 0.04%-0.4% for both LC/MS and LC/MS/MS analyses. The correlation coefficients of all linear regression lines ranged from 0.998 to 1.000. The detection limits (at a signal-to-noise ratio of approximately 3-5) were 10 and 15 pg for LC/MS and LC/MS/MS, respectively. This method, which demonstrates good accuracy and precision, and is free from interferences from structural analogues, qualifies as a candidate reference method and can be used as an alternative reference method to provide an accuracy base to which the routine methods can be compared.

Fourier transform ion cyclotron resonance mass spectrometry using atmospheric pressure photoionization for high-resolution analyses of corticosteroids

Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) was coupled with atmospheric pressure photoionization (APPI) for the first time and used for the analysis of several corticosteroids.1 The analytes showed excellent response using APPI when compared with both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). APPI has the advantage of requiring less heat for desolvation, resulting in less thermal degradation of the analytes and higher signal-to-noise than APCI. In terms of ultimate sensitivity, APPI is more efficient than either ESI or APCI for the analysis of corticosteroids. With some compounds, the high-resolution capability of FTICRMS was necessary to obtain an accurate mass due to contributions of the M(+.) (13)C isotope in the [M+H](+) ion peak.

Validation of a High-Throughput Liquid Chromatography–Tandem Mass Spectrometry Method for Urinary Cortisol and Cortisone

Background: Urinary free cortisol and cortisone measurements are useful in evaluation of Cushing syndrome, apparent mineralocorticoid excess, congenital adrenal hyperplasia, and adrenal insufficiency. To reduce analytical interference, improve accuracy, and shorten the analysis time, we developed a liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for urinary cortisol and cortisone.

Methods: We added 190 pmol (70 ng) of stable isotope cortisol-9,11,12,12-d4 to 0.5 mL of urine as an internal standard before extraction. The urine was extracted with 4.5 mL of methylene chloride, washed, and dried, and 10 μL of the reconstituted extract was injected onto a reversed-phase C18 column and analyzed using a tandem mass spectrometer operating in the positive mode.

Results: Multiple calibration curves for urinary cortisol and cortisone exhibited consistent linearity and reproducibility in the range 7–828 nmol/L (0.25–30 μg/dL). Interassay CVs were 7.3–16% for mean concentrations of 6–726 nmol/L (0.2–26.3 μg/dL) for cortisol and cortisone. The detection limit was 6 nmol/L (0.2 μg/dL). Recovery of cortisol and cortisone added to urine was 97–123%. The regression equation for the LC-MS/MS (y) and HPLC (x) method for cortisol was: y = 1.11x + 0.03 μg cortisol/24 h (r2 = 0.992; n = 99). The regression equation for the LC-MS/MS (y) and immunoassay (x) methods for cortisol was: y = 0.66x − 12.1 μg cortisol/24 h (r2 = 0.67; n = 99).

Conclusion: The sensitivity and specificity of the LC-MS/MS method for urinary free cortisol and cortisone offer advantages over routine immunoassays or chromatographic methods because of elimination of drug interferences, high throughput, and short chromatographic run time.

Rapid screening assay of congenital adrenal hyperplasia by measuring 17 alpha-hydroxyprogesterone with high-performance liquid chromatography/electrospray ionization tandem mass spectrometry from dried blood spots

A rapid, simple, and specific method was developed for the diagnosis of congenital adrenal hyperplasia (CAH) from dried blood spots on newborn screening cards based on high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS). The usefulness of 17 alpha-hydroxyprogesterone (17 OH-P) determination on dried filter-paper blood samples from patients with CAH caused by 21-hydroxylase deficiency was evaluated. The LC/MS/MS detection of 17 OH-P was rapid, <4 min. The intra- and interday accuracy and precision of the method were <7%. Our procedure maintained good linearities (R(2) > 0.992) and recovery rate (>83%). We used this new method to directly determine the 17 OH-P levels in dried blood specimens from abnormal children of various ages, with a detection limit of 20 ng/ml (approximately 240 pg), to avoid the time-consuming derivatization steps required by the gas-chromatography/mass spectrometry (GC/MS) method. Four dried filter-paper blood samples of CAH patients (three girls and one boy, 1-14 years old) were all quantified in an LC/MS/MS study and revealed high 17 OH-P levels (>90 ng/ml). After treatment, all of the elevated 17 OH-P levels either decreased or disappeared. Compared with CAH patients, 17 OH-P was nearly undetectable (<20 ng/ml) in the normal infants by LC/MS/MS. This LC/MS/MS assay is not only useful for both diagnosis and monitoring of treatment of CAH in all other age groups, it also can be used as a screening test for CAH infants. In this study, we provided the first data on 17 OH-P in dried blood specimens affected with CAH using HPLC/ESI-MS/MS.

Gas chromatography and high-performance liquid chromatography of natural steroids

This review article underlines the importance of gas chromatography (GC), high-performance liquid chromatography (HPLC) and their hyphenated techniques using mass spectrometry (MS) for the determination of natural steroids, especially in human biological fluids. Steroids are divided into eight categories based on their structures and functions, and recent references using the above methodologies for the analysis of these steroids are cited. GC and GC-MS are commonly used for the determination of volatile steroids. Although HPLC is a widely used analytical method for the determination of steroids including the conjugated type in biological fluids, LC-MS is considered to be the most promising one for this purpose because of its sensitivity, specificity and versatility.

Detection of metabolites using high-performance liquid chromatography and mass spectrometry

This unit provides a discussion of high-pressure liquid chromatography-atmospheric pressure ionization mass spectrometry (LC-API-MS) for separation, detection, and identification of products from xenobiotic metabolism. It includes an introduction and important technical information for electrospray and atmospheric pressure chemical ionization methods as well as scan modes. Emphasis has been placed on each method as related to phase I and phase II metabolite identification and there are listings of specific applications (and references) to reduce method development time.

Rapid monitoring assay of congenital adrenal hyperplasia with microbore high-performance liquid chromatography/electrospray ionization tandem mass spectrometry from dried blood spots

17-hydroxyprogesterone (17OHP) is the most important plasma parameter for diagnosing and monitoring congenital adrenal hyperplasia (CAH) caused by 21-hydroxylase deficiency. A rapid, simple, and specific method based on microbore high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (micro-HPLC/ESI-MS/MS) was developed to determine the presence of 17OHP on dried filter-paper blood samples from patients with CAH caused by 21-hydroxylase deficiency. 17OHP from dried blood spots formed by the action of Girard reagent P (GirP) turned out to be a water-soluble hydrazone complex. Derivatization with GirP led to higher ESI sensitivity for 17OHP. The LC/MS/MS detection of GirP-derivatized 17OHP (GirP-17OHP) was rapid (<3 min). The method is repeatable and reproducible, with CVs <7% and 12%, respectively. This new method was used for direct determination of 17OHP in dried blood specimens obtained from abnormal children and infants of various ages with a detection limit of 10 ng/mL ( approximately 12 microL blood). The method described allows for rapid and reliable measurements of 17OHP in dried blood specimens from patients affected by CAH.

Simultaneous determination of urinary free cortisol and 6beta-hydroxycortisol by liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry and its application for estimating hepatic CYP3A induction

A reversed-phase high-performance liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry (HPLC-APCI-MS-MS) assay was developed to simultaneously determine monkey urinary free cortisol (C) and 6beta-hydroxycortisol (6beta-OHC) in 8 min. Urine sample (0.5 ml) containing fludrocortisone acetate (F-C) as the internal standard was extracted with ethyl acetate for 5 min with an extraction efficiency of 90% and 75% for C and 6beta-OHC, respectively. A Perkin-Elmer Sciex API 3000 triple quadruple instrument was used for mass spectrometric detection and the column eluent was directed to a heated nebulizer probe. The assay was linear over the range 0.25-10 microM for each analyte. The intra- and inter-day relative standard deviation (RSD) over the entire concentration range for both analytes was less than 10%. Accuracy determined at three concentrations (0.8, 2.0 and 8.0 microM) ranged between 95.5 and 108%. The method described herein is suitable for the rapid and efficient measurement of 6beta-OHC/C ratio in Rhesus monkey urine following administration of known hepatic CYP3A inducers and can be used to estimate potential CYP3A induction by drug candidates in the process of early drug development.

Collision-induced dissociation of corticosteroids in electrospray tandem mass spectrometry and development of a screening method by high performance liquid chromatography/tandem mass spectrometry

A screening method based on liquid chromatography/electrospray tandem mass spectrometry was developed in order to control the illegal use of corticosteroids as growth promoters in cattle. The objective was the detection of low residue levels of corticosteroids or metabolites in biological matrices. Relative to other studies published on this subject, the present work focused on enhancing specificity and sensitivity. Firstly, fragmentation of corticosteroids by collision-induced dissociation was studied. In positive mode, the losses of H(2)O for each hydroxyl group fixed on the molecule, as well as the loss of HF or HCl for halogenated compounds, were observed. For higher collision energy, fragmentations in the B, C and D rings were induced. The negative mode was found to be more specific, inducing a cleavage of the C(20)-C(21) bond with concomitant loss of formaldehyde (CH(2)O). Secondly, three acquisition methods in the negative mode were studied and evaluated, recorded signals being the parent ion [M + acetate](-) and the two daughter ions, [M - H](-) and [M - H - CH(2)O](-). For dexamethasone, MS/MS instrumental detection limits of fragment ion and neutral loss scans, and of multiple reaction monitoring (MRM), were 250, 20 and 5 pg injected, respectively. The MRM method was then evaluated with the objective of use for the detection of corticosteroid residues in biological samples (urine, hair, muscle) and for a metabolism study.

Separation and identification of corticosterone metabolites by liquid chromatography--electrospray ionization mass spectrometry

High-performance liquid chromatography coupled to atmospheric pressure ionization-electrospray ionization mass spectrometry (API-ESI-MS) was investigated for the analysis of corticosterone metabolites; their characterization was obtained by combining the separation on Zorbax Eclipse XDB C18 column (eluted with a methanol-water-acetic acid gradient) with identification using positive ion mode API-ESI-MS and selected ion analysis. The applicability of this method was verified by monitoring the activity of steroid converting enzymes (20beta-hydroxysteroid dehydrogenase and 11beta-hydroxysteroid dehydrogenase) in avian intestines.

A reference method for the analysis of aldosterone in blood by high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry

A high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (HPLC-APCI-MS/MS) reference method for the quantitation of aldosterone in serum and plasma has been developed. Samples were extracted with dichloromethane/diethyl ether, containing flumethasone as internal standard (IS). Chromatography was performed on a phenyl column using 50 mm ammonium formate (pH 7.1)/methanol (50/50, v/v) as mobile phase. Analysis was in negative-ionization mode by selected reaction monitoring (aldosterone m/z 359.2 --> 331.2; IS m/z 455.0 --> 379.0). The assay was linear over the range 15-500 pg/mL, with limits of detection and quantitation of 10 and 15 pg/mL, respectively. Imprecisions of the assay at 15, 20, 150, and 450 pg/mL were 18.5, 8. 8, 10.6, and 9.5%, respectively. The accuracy of the method ranged from 93.1 to 98.9% with absolute recoveries between 84.0 and 91.3% (aldosterone) and 88.0 and 92.3% (IS). We present a case study of a patient admitted, with suspected primary hyperaldosteronism, on the basis of a high radioimmunoassay (RIA) aldosterone concentration. The results suggest that RIA was unreliable, causing unnecessary patient discomfort and a costly 6-day hospital stay. The specific HPLC-API-MS/MS assay described offers the sensitivity and accuracy required to assess abnormal aldosterone production in hypertensive patients.

Cortisol metabolism and its inhibition by glycyrrhetinic acid in the isolated perfused human placental lobule

We have previously reported the placental metabolism of prednisolone to prednisone, 20alpha- and beta-dihydroprednisone and 20beta-dihydroprednisolone. In this study, the disposition of cortisol was investigated in vitro in the dual perfused, isolated human placental lobule after the addition of cortisol (1.2 micromol, n = 3 and 12 micromol, n = 4) to the maternal compartment. Analysis of 5 h maternal and fetal perfusate samples by high performance liquid chromatography-electrospray-tandem mass spectrometry (HPLC-ESI-MS/MS) revealed that cortisol was mainly metabolized to cortisone, but a significant production of 20alpha-dihydrocortisone, 20beta-dihydrocortisone, 20alpha-dihydrocortisol and 20beta-dihydrocortisol was also detected. Saturability of metabolism but not transfer was demonstrated. Metabolism was eliminated by co-perfusion with the potent 11beta-hydroxysteroid dehydrogenase (11beta-HSD) enzyme inhibitor 18beta-glycyrrhetinic acid (GA). The disposition of GA was analysed using HPLC-atmospheric pressure chemical ionisation-MS/MS (HPLC-APCI-MS/MS). GA was found to transfer from the maternal to the fetal circulations without detectable metabolism during 6 h of perfusion.