Gas chromatographic-mass spectrometric identification of 16alpha-hydroxy-dehydroepiandrosterone in human seminal plasma

Occurrence and reproductive roles of hormones in seminal plasma

Only 2-5% of seminal fluid is composed of spermatozoa, while the rest is seminal plasma. The seminal plasma is a rich cocktail of organic and inorganic compounds including hormones, serving as a source of nutrients for sperm development and maturation, protecting them from infection and enabling them to overcome the immunological and chemical environment of the female reproductive tract. In this review, a survey of the hormones found in human seminal plasma, with particular emphasis on reproductive hormones is provided. Their participation in fertilization is discussed including their indispensable role in ovum fertilization. The origin of individual hormones found in seminal plasma is discussed, along with differences in the concentrations in seminal plasma and blood plasma. A part of review is devoted to methods of measurement, emphasising particular instances in which they differ from measurement in blood plasma. These methods include separation techniques, overcoming the matrix effect and current ways for end-point measurement, focusing on so called hyphenated techniques as a combination of chromatographic separation and mass spectrometry. Finally, the informative value of their determination as markers of male fertility disorders (impaired spermatogenesis, abnormal sperm parameters, varicocele) is discussed, along with instances where measuring their levels in seminal plasma is preferable to measurement of levels in blood plasma.

Determination of seven selected neuro- and immunomodulatory steroids in human cerebrospinal fluid and plasma using LC-MS/MS

Dehydroepiandrosterone (DHEA) and its 7-oxo- and 7-hydroxy-metabolites occurring in the brain are considered neurosteroids. Metabolism of the latter is catalysed by 11β-hydroxysteroid dehydrogenase (11β-HSD) which also interconverts cortisol and cortisone. The concurrent metabolic reaction to DHEA 7-hydroxylation is the formation of 16α-hydroxy-DHEA. The LC-MS/MS method using triple stage quadrupole-mass spectrometer was developed for simultaneous quantification of free DHEA, 7α-hydroxy-DHEA, 7β-hydroxy-DHEA, 7-oxo-DHEA, 16α-hydroxy-DHEA, cortisol and cortisone in human plasma and cerebrospinal fluid (CSF). The method employs 500 μL of human plasma and 3000 μL of CSF extracted with diethyl ether and derivatized with 2-hydrazinopyridine. It has been validated in terms of sensitivity, precision and recovery. In plasma, the following values were obtained: limit of detection: 2-50p g/mL; limit of quantification: 5-140 pg/mL; within-day precision 0.58-14.58%; between-day precision: 1.24-13.89% and recovery: 85-113.2%). For CSF, the values of limit of detection: 2-28 pg/mL; limit of quantification: 6-94 pg/mL; within-day precision; 0.63-5.48%; between-day precision: 0.88-14.59% and recovery: 85.1-109.4% were acquired. Medians and concentration ranges of detected steroids in plasma and CSF are given in subjects with excluded normal pressure hydrocephalus (n=37; 65-80 years). The method enables simultaneous quantification of steroids important for the estimation of 11β-HSD activity in human plasma and CSF. It will be helpful in better understanding various degenerative diseases development and progression.

Mechanistic aspects of rearrangement of 16alpha-hydroxy-17-keto steroids to the 17beta-hydroxy-16-keto isomers

The mechanistic aspects of the alkali-catalyzed rearrangement of 16alpha-hydroxy-17-keto steroid 1 to 17beta-hydroxy-16-keto steroid 2 are elucidated by use of (18)O- and deuterium-labeling experiments. The (18)O-labeling experiments refute the gem-hydration-quasi-diaxial dehydration mechanism for the rearrangement previously proposed and support the conventional enolization mechanism. Moreover, equilibrium by gem-hydration-dehydration occurs at the C-17 carbonyl more efficiently than at the C-16 carbonyl. Enolization rate of a carbonyl group at C-16 of 17beta-ketol 2 toward the C-17 position (k(16,17)) was about 8-10 times higher than those of 16alpha-ketol 1 toward the C-16 position (k(17,16)) and ketol 2 toward the C-15 position (k(16,15)). The marked deuterium-isotope effect on each enolization was observed with k(H)/k(D) ranging between 5.4 and 8.8. The present findings reveal that the initial hydration-dehydration equilibration at the C-17 carbonyl of ketol 1 followed by enolization of the carbonyl gives the ene-diol intermediate that isomerizes quantitatively to the 16-keto isomer of which the 16-carbonyl moiety enolizes preferentially toward the C-17 position rather than the C-15 position, yielding the ene-diol. Computational calculations of ground state energies of ketols 1-M and 2-M, trans-cyclohexane/cyclopentane structures, and their activation energies in the rearrangement support the dynamic aspects of the rearrangement as well as the kinetics data of the enolization.

A novel radioimmunoassay of 16alpha-hydroxy-dehydroepiandrosterone and its physiological levels

16alpha-Hydroxy-dehydroepiandrosterone (16alpha-OH-DHEA) belongs to the products of extensive DHEA metabolism in mammalian tissues. It is a precursor of 16alpha-hydroxylated estrogens, increased levels of which are associated with autoimmune disorders. A highly specific radioimmunoassay of unconjugated 16alpha-OH-DHEA was developed and evaluated. Polyclonal rabbit antisera were raised against 3beta,16alpha-dihydroxy-17,19-dione-19-O-(carboxymethyloxime) and 3beta,16alpha-dihydroxy-7,17-dione-7-O-(carboxymethyloxime) BSA conjugates. Two methods were used for preparation of the conjugates. Homologous radioiodinated derivatives with tyrosine methyl ester were prepared as tracers. While antisera to 7-CMO cross-reacted with DHEA as much as by 58%, the cross-reaction of the chosen antiserum prepared via 19-oxogroup by micellar conjugation technique with 16beta-OH-DHEA was only 0.13% and with all other structurally related steroids, including DHEA were lower than 0.01%. The detection limit was 0.017 pmol (5.7 pg)/tube, the average intra- and inter-assay coefficients of variation were 8.2 and 11.4%, respectively. Mean recovery of serum spiked with 16alpha-OH-DHEA varied between 80 and 110%, the results were independent on sample dilution. 16alpha-OH-DHEA concentrations in 18 randomly selected sera, including 6 samples from patients with thyroid cancer were compared with results obtained by earlier GC-MS method. Physiological levels of 16alpha-OH-DHEA in 316 sera (184 females and 132 males) analyzed so far varied between 0.0 and 1.86 nmol/l.