Derivatization-based quadruplex LC/ESI-MS/MS method for high throughput quantification of serum dehydroepiandrosterone sulfate

Determination of three C18-oxygenated steroids in adrenal lesion segments in primary aldosteronism by super-selective adrenal venous sampling and LC/ESI-MS/MS

Super-selective adrenal venous sampling (ssAVS) can collect the adrenal tributary venous blood in the aldosterone (ALD)-hypersecreting segments in primary aldosteronism. The concentrations of the C18-oxygenated steroids, especially 18-oxocortisol (18-oxoF), in the lesion segments might be more useful indices than those in the peripheral or adrenal central veins (current candidate indexes) for the differential diagnosis of unilateral ALD-producing adenoma (APA) and bilateral adrenal hyperplasia (BAH). To verify this hypothesis, we developed a liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) method for simultaneously quantifying ALD, 18-oxoF and 18-hydroxycortisol in the adrenal tributary venous serum sample collected by ssAVS (ssAVS serum) and compared their concentrations between APA and BAH patients. Only deproteinization was required for a 10 μl sample prior to the LC/ESI-MS/MS analysis. Endogenous corticoids did not interfere with the quantifications, and the intra-assay and interassay precisions (≤ 8.3%) and accuracies (94.2-102.7%) were acceptable. The clinical study revealed that the 18-oxoF concentration was significantly higher in the ALD-producing tumor tissues (from APA patients) than in the hyperplastic tissues (from BAH patients). However, in conclusion, the 18-oxoF concentration in the ssAVS serum sample can be a rough indication but cannot be decisive for the differential diagnosis between APA and BAH owing to the significant individual difference.

Methylation of phase II metabolites of endogenous anabolic androgenic steroids to improve analytical performance

The study of intact phase II metabolites of endogenous anabolic androgenic steroids (EAAS) gives important information about metabolism and has the potential to improve the detection of doping with testosterone. For analysis with liquid chromatography-mass spectrometry (LC-MS), chemical derivatization at the steroid moiety is a technique to improve the positive ionization efficiency of glucuronidated/sulfated EAAS under collision-induced dissociation (CID) conditions. However, regarding the chromatographic performance, there are still challenges to address, for example, poor peak shape, which is mainly caused by nondefined adsorption in the chromatographic system. Here, we show a novel derivatization technique for the analysis of selected phase II metabolites of EAAS, where the acidic moiety of the glucuronide/sulfate is methylated with different methylation reagents to reduce nondefined adsorption. The methylation reagent trimethylsilyl-diazomethane (TMSD) was preferred over the other tested reagents methyl iodide (MeI) and dimethyl sulfate (DMS). Glucuronidated and sulfated testosterone and epitestosterone were methylated, and their chromatographic performance and CID ion mass spectra obtained in positive ionization mode were investigated. The peak width and peak height were significantly improved for all substances. Methylated testosterone sulfate showed the best results with a 3.5 times narrower peak and 14 times increased intensity compared with underivatized testosterone sulfate. Furthermore, CID ion mass spectra obtained in positive ionization mode showed product ions characteristically for the steroidal backbone for all substances. This preliminary study shows the potential of methylation as a supplementary derivatization technique, which can assist in the development of more sensitive methods due to the improvements in method performance.

Drugs possessing aryloxypropanamine pharmacophore, duloxetine, dapoxetine and propranolol, increase allopregnanolone in rat brain: Possible involvement of allopregnanolone in their central nervous system effects

Allopregnanolone (AP) is a neurosteroid synthesized in the brain and a positive allosteric modulator of γ-aminobutyric acid (GABA) type A receptors. Some drugs possessing the aryloxypropanamine (AOPA) pharmacophore, such as fluoxetine, exert their central nervous system (CNS) effects by increasing the brain AP. Although duloxetine (DLX), dapoxetine (DPX), atomoxetine (ATX) and propranolol (PRL) also possess the AOPA pharmacophore and are used to treat some psychiatric disorders, the capabilities of these drugs to increase the brain AP and the possible involvement of AP in their CNS effects remain to be fully elucidated. To clarify these points, we first developed a method for quantifying AP in the rat brain by liquid chromatography/electrospray ionization-tandem mass spectrometry. Analysis of the changes in the brain AP levels using this method revealed that the intraperitoneal administration of DLX (10 mg/kg), DPX (10 mg/kg) and PRL (20 mg/kg) significantly increased the brain AP (DLX: < 0.40-2.74 ng/g tissue, DPX: 1.48-3.83 ng/g tissue and PRL: < 0.40-2.09 ng/g tissue) compared to the saline administration (<0.40 ng/g tissue). These results suggested the possible involvement of the GABAergic neurosteroid, AP, in the central actions of DLX, DPX and PRL. In contrast, ATX (10 mg/kg) did not affect the AP levels in the brain. In addition, the brain and serum AP levels had a remarkably high positive correlation after the administration of DLX, DPX and PRL. Thus, this study proposed the AP-related novel mechanism of actions of DLX, DPX and PRL in the CNS.

Improved Ion Mobility Separation and Structural Characterization of Steroids using Derivatization Methods

Steroids are an important class of biomolecules studied for their role in metabolism, development, nutrition, and disease. Although highly sensitive GC- and LC-MS/MS-based methods have been developed for targeted quantitation of known steroid metabolites, emerging techniques including ion mobility (IM) have shown promise in improved analysis and capacity to better identify unknowns in complex biological samples. Herein, we couple LC-IM-MS/MS with structurally selective reactions targeting hydroxyl and carbonyl functional groups to improve IM resolution and structural elucidation. We demonstrate that 1,1-carbonyldiimidazole derivatization of hydroxyl stereoisomer pairs such as testosterone/epitestosterone and androsterone/epiandrosterone results in increased IM resolution with ΔCCS > 15%. Additionally, performing this in parallel with derivatization of the carbonyl group by Girard's Reagent P resulted in unique products based on relative differences in number of each functional group and C17 alkylation. These changes could be easily deciphered using the combination of retention time, collision cross section, accurate mass, and MS/MS fragmentation pattern. Derivatization by Girard's Reagent P, which contains a fixed charge quaternary amine, also increased the ionization efficiency and could be explored for its potential benefit to sensitivity. Overall, the combination of these simple and easy derivatization reactions with LC-IM-MS/MS analysis provides a method for improved analysis of known target analytes while also yielding critical structural information that can be used for identification of potential unknowns.

A method for determination of aldosterone concentrations of six adrenal venous serum samples during a single LC/ESI-MS/MS run using a sextet of Girard reagents

The accurate quantification of aldosterone (ALD) in adrenal tributary venous serum/plasma collected by a super-selective adrenal venous sampling (ssAVS) technique has become a definitive procedure to identify the forms (laterality) of primary aldosteronism (PA) and the location of the affected segment(s), and to subsequently make the treatment decision. In this study, a stable isotope-dilution LC/ESI-MS/MS-based method was developed and validated for the determination of the ALD concentrations of the six ssAVS serum samples during a single run. A sextet of Girard reagents was used to convert ALD to the derivatives having different masses for each sample. Based on the validation tests, satisfactory specificity, precision and accuracy were observed and the matrix effect was found to be acceptable. The developed method was used for the analysis of the ssAVS serum samples from eight PA patients. The batch analysis of the six samples permitted the direct comparison of the ALD concentrations between the samples and enhanced to determine the laterality and location of the affected segment(s). The total analysis time after the sample purification was also reduced to 1/3 for the 24 samples by the sample-sextuplex procedure, which was also an advantage of the developed method.