The quantification of endogenous steroids in bovine aqueous humour and vitreous humour using isotope dilution GC-NCI-MS

The effects of female sex hormones on the human cornea across a woman's life cycle

The cornea is a hormone-responsive tissue that responds to changing levels of female sex hormones. This review focuses on the structural and functional changes in the human cornea associated with the hormonal milestones of menarche, pregnancy, and menopause, as well as consequences stemming from the use of exogenous sex hormones for fertility control and replacement. Articles were identified by searching PubMed without language or region restrictions. The primary outcomes evaluated were changes in central corneal thickness (CCT), intraocular pressure (IOP), and quality of the ocular tear film. The potential impact of hormone-associated changes on the diagnosis and surgical management of common eye diseases, as well as the potential use of sex hormones as therapeutic agents is also considered. Understanding the physiological effects of female sex hormones on the cornea is important because that knowledge can shape the management decisions physicians and women face about ocular health across their life stages.

Sex Hormones, Growth Hormone, and the Cornea

The growth and maintenance of nearly every tissue in the body is influenced by systemic hormones during embryonic development through puberty and into adulthood. Of the ~130 different hormones expressed in the human body, steroid hormones and peptide hormones are highly abundant in circulation and are known to regulate anabolic processes and wound healing in a tissue-dependent manner. Of interest, differential levels of sex hormones have been associated with ocular pathologies, including dry eye disease and keratoconus. In this review, we discuss key studies that have revealed a role for androgens and estrogens in the cornea with focus on ocular surface homeostasis, wound healing, and stromal thickness. We also review studies of human growth hormone and insulin growth factor-1 in influencing ocular growth and epithelial regeneration. While it is unclear if endogenous hormones contribute to differential corneal wound healing in common animal models, the abundance of evidence suggests that systemic hormone levels, as a function of age, should be considered as an experimental variable in studies of corneal health and disease.

Quantification and comparison of baseline cortisol levels between aqueous and plasma from healthy anesthetized hound dogs utilizing mass spectrometry

OBJECTIVE

The purpose of this study is to quantify and compare the resting cortisol levels between aqueous (Aq) and plasma of anesthetized hound dogs utilizing mass spectrometry.

ANIMALS

Nine hound breed dogs weighing between 20.8 and 29.2 kg (x = 26.3 kg, SD ± 2.6 kg) were utilized from a previous project.

PROCEDURES

All dogs underwent two anesthesia sessions to harvest Aq from each eye respectively. A paired blood sample was taken immediately after aqueous centesis. The Aq and plasma were analyzed for cortisol levels using mass spectrometry. Correlation of cortisol levels in dog serum and ocular fluid was determined with Sigma Stat using Pearson's correlation analysis. The level of significance for correlation analysis was set at P < 0.05.

RESULTS

The plasma resting cortisol levels in the dog ranged from 3.59 to 89.35 nm (x = 31.68 nm, SD ± 28.53 nm), while the Aq cortisol levels ranged from 0.82 to 5.62 nm (x = 2.73 nm, SD ± 1.94 nm). The correlation of cortisol levels in Aq compared to plasma was significant (P = 0.008) with a correlation coefficient of r = 0.779. Based on these results, 61% (r = 0.779(2) ) of the variation in Aq cortisol levels is explained by the variations in plasma cortisol levels.

CONCLUSION AND CLINICAL RELEVANCE

This study identified significant levels of cortisol in the Aq of the canine eye and positively correlated them with plasma cortisol levels. The dog may offer a representative model for further studies to help clarify the overall role of cortisol in the anterior chamber.

Use of novel picolinoyl derivatization for simultaneous quantification of six corticosteroids by liquid chromatography-electrospray ionization tandem mass spectrometry

Simultaneous quantification method of six corticosteroids, cortisone, cortisol, cortexolone, corticosterone, dehydrocorticosterone and deoxycorticosterone, by LC-electrospray ionization (ESI)-MS in a positive mode using novel picolinoyl derivatization was investigated. Conversion of each corticosteroid into the corresponding picolinoyl derivative was performed by mixed anhydride method using picolinic acids and 2-methyl-6-nitrobenzoic anhydride. Derivatization proceeded smoothly to afford the corresponding 21-monopicolinoyl derivatives. Positive ion-ESI mass spectra of the picolinoyl derivatives were dominated by the appearance of [M+H](+) as base peaks. The picolinoyl derivatives provided 5-10 times higher ESI response in the LC-ESI-MS-selected reaction monitoring (SRM) when compared to those of underivatized molecules in a positive LC-ESI-MS mode. The use of the picolinoyl ester, solid-phase extraction, and deuterium labeled internal standards enabled to determine the concentrations of these corticosteroids in human saliva simultaneously by LC-ESI-MS-SRM.

Comparison of the use of anionic and cationic surfactants for the separation of steroids based on MEKC and sweeping-MEKC modes

In attempts to improve the selectivity and sensitivity of steroid separation and to determine their migration order, a comparison of the use of anionic and cationic surfactants based on the MEKC and sweeping-MEKC modes was made. A mixture of six steroids (progesterone, 17-hydroxy progesterone, 11-deoxycortisol, corticosterone, cortisone, and cortisol) could be separated and detected by means of the CE/UV-absorption method. The order of migration time for these steroids was compared under various conditions, including acidic/alkaline buffers, anionic/cationic surfactants, and positive/negative applied voltage, causing the direction of the EOF and the migration of micelles to change. The major rules for generally predicting the migration order of steroids are summarized. The detection limits were significantly improved when the sweeping-MEKC mode was applied.

Determination of corticosterone and 17-hydroxycorticosterone in plasma and urine samples by sweeping techniques using micellar electrokinetic chromatography

The analysis of corticosterone in mouse blood serum (metabolic-stress experiment) and 17-hydroxycorticosterone in human urine (exercise-stress experiment) samples by means of capillary electrophoresis/UV absorbance in conjunction with online sample concentration techniques is described. The use of normal MEKC had an analyte detection limit of 7 microg/ml (S/N=3); whereas when online sample concentration methods, including sweeping-micellar electrokinetic chromatography (Sweeping-MEKC) and cation-selective exhaustive injection-sweep-micellar electrokinetic chromatography (CSEI-sweep-MEKC) were used, the detection limits could be improved to 3 and 5 ng/ml, respectively. In the analysis of actual samples from animal metabolic-stress experiments (39 mouse), chronically stressed animals showed a higher level (552+/-152 ng/ml) and acute stressed animals showed an intermediate level (375+/-105 ng/ml). In comparison, normal animals show a lower concentration level of corticosterone (153+/-109 ng/ml). In addition, based on a human exercise-stress experiment (seven volunteers), the acute stressed humans (after exercise, 800 m of running) show a higher concentration of 17-hydroxycorticosterone (113+/-55 ng/ml for males; 128+/-25 for females) and the non-stressed humans (before exercise) show a lower concentration (63+/-37 ng/ml for male; 60+/-20 for female), respectively.

Determination of corticosterone in rat and mouse plasma by gas chromatography-selected ion monitoring mass spectrometry

A simple, highly sensitive and specific method based on gas-chromatography-selected ion monitoring (SIM) mass spectrometry has been developed for the quantitation of corticosterone in rat and mouse plasma. After extraction of the plasma with ethyl acetate, the residue was trimethy-silylated with pentafluorobenzyl hydroxylamine-trimethylsilyl (PFBO-TMS). Detection of the derivatives was accomplished by a quadruple mass spectrometer in the selected ion monitoring mode (m/z of 316, 648, 663 and 678). The detection limit of the assay was 0.1 pg on column. The results show that in the plasma of non-stressed animals, only minor amounts of corticosterone were found; whereas in the plasma of stressed animals, it was dramatically increased. The method developed here can be used to examine corticosterone levels as a marker of stress in rats and mice and may also be used for estimation of the effect of stress-release medications.

Relationship between the concentration of copper and iron in the aqueous humour and intraocular pressure in rabbits treated with topical steroids

PURPOSE

To evaluate the concentration of copper and iron in the aqueous humour of steroid-treated eyes, particularly to study the concentration of these metals in relation to steroid-induced increases in intraocular pressure (IOP).

METHODS

Adult rabbits of both sexes were selected in order to study the effect of steroids on the concentrations of copper and iron in the aqueous humour and on IOP. The rabbits were acclimatised for 2 weeks prior to the instillation of various drugs into the eyes. Then a steroid (dexamethasone, betamethasone or fluoromethalone) was instilled in both eyes of the rabbits, for about 1 month. Intraocular pressure was measured twice a week. When IOP was significantly increased, the animals were killed. The aqueous humour was collected and analysed for copper and iron using atomic absorption spectrophotometry coupled with graphite fumace.

RESULTS

After about 30 days of steroid treatment the mean (+/- SD) IOP in dexamethasone, betamethasone and fluoromethalone treated groups was 17.5 (+/- 4.81) mmHg, 18.48 (+/- 4.5) mmHg and 21.8 (+/- 5.7) mmHg, respectively. These values were significantly higher compared to the control group where the mean IOP was 11.6 (+/- 2.2) mmHg. The concentration of copper in the aqueous humour of steroid-treated rabbits was significantly lower (P < 0.001) compared to the control group. However, the concentration of iron was not significantly different between the control and steroid treated rabbits.

CONCLUSION

A greater increase in IOP was observed in the fluoromethalone-treated group compared to the dexamethasone and betamethasone-treated groups, but the difference was not significant. The lower concentrations of copper in aqueous humour in steroid-treated eyes may play an important role in the maintenance of IOP. The concentration of iron was not significantly different compared to the control group. These results may help to explain the role of these metals in the pathogenesis of open angle glaucoma.