Testicular induced corticosterone synthesis in male rats under fasting stress

Testicular steroidogenesis is depressed by adrenal-secreted corticosterone (CORT) under stress. However, the mechanisms are not well understood. This study investigated the details of testicular steroidogenesis depression during fasting. Blood levels of adrenocorticotropic hormone secreted from the pituitary glands increased, but blood CORT was not changed in rats that fasted for 96 h, in spite of the rats being severely stressed. CORT in fasting adult male rats increased more than three times in the testis, but reduced testicular testosterone (T) and blood T levels to 5% and 2% of the control, respectively, was observed. The contents of T precursor (except PGN) were drastically reduced in the fasted-rat testes. Testicular CORT levels were elevated, but the enzymatic activity of cytochrome P45011β, which produces CORT, remained unchanged. The enzymatic activities of 3β-hydroxysteroid dehydrogenase (3β-HSD), mediating the conversion of pregnenolone to progesterone, decreased in the fasted-rat testes. Thus, fasting suppressed testicular steroidogenesis by affecting the enzyme activity of 3β-HSD in the testes and drastically reduced T and increased CORT synthesis. It can be considered that T synthesis involved in cell proliferation is suppressed due to lack of energy during fasting. Conversely, 11β-hydroxylase enzyme activity was induced and CORT synthesis is increased to cope with the fasting stress. Hence, it can be concluded that CORT synthesis in the testes plays a role in the local defense response.

Quantitative analysis of 11-dehydrocorticosterone and corticosterone for preclinical studies by liquid chromatography/triple quadrupole mass spectrometry

RATIONALE

The activity of the glucocorticoid activating enzyme 11β-hydroxysteroid dehydrogenase type-1 (11βHSD1) is altered in diseases such as obesity, inflammation and psychiatric disorders. In rodents 11βHSD1 converts inert 11-dehydrocorticosterone (11-DHC) into the active form, corticosterone (CORT). A sensitive, specific liquid chromatography/tandem mass spectrometry method was sought to simultaneously quantify total 11-DHC and total and free CORT in murine plasma for simple assessment of 11βHSD1 activity in murine models.

METHODS

Mass spectrometry parameters were optimised and a method for the chromatographic separation of CORT and 11-DHC was developed. Murine plasma was prepared by 10:1 chloroform liquid-liquid extraction (LLE) for analysis. Limits of quantitation (LOQs), linearity and other method criteria were assessed, according to bioanalytical method validation guidelines.

RESULTS

Reliable separation of 11-DHC and CORT was achieved using an ACE Excel 2 C18-AR (2.1 × 150 mm; 2 μm) fused core column at 25°C, with an acidified water/acetonitrile gradient over 10 min. Analytes were detected by multiple reaction monitoring after positive electrospray ionisation (m/z 345.1.1 ➔ 121.2, m/z 347.1 ➔ 121.1 for 11-DHC and CORT, respectively). The LOQs were 0.25 and 0.20 ng/mL for 11-DHC and CORT, respectively.

CONCLUSIONS

This LC/MS method is suitable for the reliable analysis of 11-DHC and CORT following simple LLE of murine plasma, bringing preclinical analysis in line with recommendations for clinical endocrinology and biochemistry.

Posthatching Parental Care and Offspring Growth Vary with Maternal Corticosterone Level in a Wild Bird Population

Corticosterone is the primary metabolic steroid in birds and is vital for maintaining homeostasis. However, the relationship between baseline corticosterone and reproduction is unclear, and we lack an understanding of how differences in baseline corticosterone at one stage of the breeding cycle influence reproductive effort at later stages. In a wild population of house wrens, we quantified the concentration of corticosterone in yolks of freshly laid eggs as an integrated measure of maternal physiology and related this to a behavioral measure of stress reactivity made during the nestling period, namely, the latency with which females resumed parental activities following a standardized disturbance at their nest (setting up a camera to record provisioning). Females that recently produced eggs containing higher corticosterone concentrations, which were significantly repeatable within females, took longer to resume activity related to parental care (i.e., feeding and brooding young) following the disturbance. Moreover, a female's latency to resume parental activities negatively predicted her provisioning of nestlings with food and the condition of these young at fledging but did not predict the number fledged. We cross-fostered offspring prior to hatching so these effects on maternal behavior are independent of any prenatal maternal effects on nestlings via the egg. These results are consistent with earlier findings, suggesting that females with higher baseline corticosterone during egg laying or early incubation tend to prioritize self-maintenance over reproduction compared with females with lower baseline corticosterone and suggest that a female's latency to return to her nest and resume parental care following a disturbance might represent a simple, functional measure of maternal stress reactivity.

Corticosterone in Lizard Egg Yolk Is Reduced by Maternal Diet Restriction but Unaltered by Maternal Exercise

When females face adverse environmental conditions, physiological changes, such as elevated corticosterone levels, to cope with the stressors may also impact their offspring. Such maternal effects are often considered adaptive and may "prime" the offspring for the same adverse environment, but maternal corticosterone levels do not always match that of the eggs produced. We examined how diet restriction and increased locomotor activity, via exercise training, affected steroid hormone levels of female green anole lizards, as well as the hormone levels in the yolk of their eggs. Diet restriction did not affect female hormone levels, but training increased corticosterone levels. Despite this, training did not affect yolk steroid levels, but eggs from females with diet restriction had lower corticosterone levels in yolk. This suggests that two common stressors, food shortage and increased locomotor activity, impact female physiology in a way that is not translated to her offspring.

Measurement of 11-dehydrocorticosterone in mice, rats and songbirds: Effects of age, sex and stress

Glucocorticoids (GCs) are secreted into the blood by the adrenal glands and are also locally-produced by organs such as the lymphoid organs (bone marrow, thymus, and spleen). Corticosterone is the primary circulating GC in many species, including mice, rats and birds. Within lymphoid organs, corticosterone can be locally produced from the inactive metabolite, 11-dehydrocorticosterone (DHC). However, very little is known about endogenous DHC levels, and no immunoassays are currently available to measure DHC. Here, we developed an easy-to-use and inexpensive immunoassay to measure DHC that is accurate, precise, sensitive, and specific. The DHC immunoassay was validated in multiple ways, including comparison with a mass spectrometry assay. After assay validations, we demonstrated the usefulness of this immunoassay by measuring DHC (and corticosterone) in mice, rats and song sparrows. Overall, corticosterone levels were higher than DHC levels across species. In Study 1, using mice, we measured steroids in whole blood and lymphoid organs at postnatal day (PND) 5, PND23, and PND90. Corticosterone and DHC showed distinct tissue-specific patterns across development. In Studies 2 and 3, we measured circulating corticosterone and DHC in adult rats and song sparrows, before and after restraint stress. In rats and song sparrows, restraint stress rapidly increased circulating levels of both steroids. This novel DHC immunoassay revealed major changes in DHC concentrations during development and in response to stress, which have important implications for understanding GC physiology, effects of stress on immune function, and regulation of local GC levels.

Challenges, pitfalls and surprises: development and validation of a monoclonal antibody for enzyme immunoassay of the steroid 1α-hydroxycorticosterone in elasmobranch species

Sharks and rays are popular species used in wildlife ecotourism and aquariums to educate the public on the behavior, ecology and conservation challenges of elasmobranchs. To understand long-term physiological health and welfare under varying social and husbandry conditions, we developed and validated an enzyme immunoassay (EIA) to measure stress/ionoregulatory hormones in managed and semi-free range southern rays (Hypanus americanus). Banked serum and interrenal samples from 27 female rays managed at Disney's The Seas with Nemo and Friends® and Castaway Cay were used to evaluate measurement of 1α-hydroxycorticosterone (1αOHB) relative to corticosterone (B). Although commercial EIAs are available for B, those tested exhibit only low relative cross-reactivity to 1αOHB (3-5%). To improve measurement of 1αOHB, we developed a monoclonal antibody using a synthesized 1αOHB-derivative for evaluation using high-performance liquid chromatography (HPLC) and EIA. Relative displacements of cross-reactant compounds showed that the antibody had good sensitivity for the target antigen 1αOHB, and low sensitivity to related steroids (desoxycorticosterone and B), but greater sensitivity to 11-dehydrocorticosterone. Tests of competitive vs. noncompetitive EIA formats, reagent titration, and incubation times of the antibody and conjugate were used to optimize sensitivity, repeatability and precision of measured 1αOHB in standards and samples (4 ng/ml, 90% binding). Tests of sample pre-treatment (pH adjustment) and extraction with varying solvent polarity were used to optimize measurement of 1αOHB in <1 ml (serum) or 1 g (interrenal) samples. HPLC analysis revealed the 1αOHB EIA to be superior for measurement of 1αOHB compared to use of a B EIA with or without HPLC fractioning. Results may prove useful for extrapolation to guide best practices for 1αOHB measurement in other elasmobranch species. Improved measurement of stress/ionoregulatory hormones in sharks and rays will be important for many aspects of collection, transport, medical treatment in aquaria and conservation management of these charismatic and ecologically important species.

Bioconversion of Corticosterone into Corticosterone-Glucoside by Glucosyltransferase

Glucosylation of the 21-hydroxyl group of glucocorticoid changes its solubility into hydrophilicity from hydrophobicity and, as with glucocorticoid glucuronides as a moving object in vivo, it is conceivable that it exhibits the same behavior. Therefore, glucosylation to the 21-hydroxyl group while maintaining the 11β-hydroxyl group is particularly important, and glucosylation of corticosterone was confirmed by high-resolution mass spectrometry and 1D (¹H and ¹³C) and 2D (COSY, ROESY, HSQC-DEPT and HMBC) NMR. Moreover, the difference in bioactivity between corticosterone and corticosterone 21-glucoside was investigated in vitro. Corticosterone 21-glucoside showed greater neuroprotective effects against H₂O₂-induced cell death and reactive oxygen species (ROS) compared with corticosterone. These results for the first time demonstrate that bioconversion of corticosterone through the region-selective glucosylation of a novel compound can present structural potential for developing new neuroprotective agents.

The impact of the clinical CYP11B2 mutation V386A strongly depends on the enzyme's genetic background

Human cytochrome P450 11B2 (CYP11B2) is an essential enzyme in the steroid hormone biosynthesis, which catalyzes the last three reaction steps of the aldosterone synthesis. These reactions comprise a hydroxylation at position C11 of the steroid intermediate deoxycorticosterone yielding corticosterone, followed by a hydroxylation at position C18 yielding 18-hydroxy-corticosterone and a subsequent oxidation of the hydroxyl group at C18, which results in the formation of aldosterone. Alterations in the amino acid sequence of CYP11B2 often cause severe disease patterns. We previously described a procedure for expression and purification of human CYP11B2 employing recombinant E. coli, which allows the rapid characterization of CYP11B2 mutants on a molecular level. This system was now utilized for the examination of the influence of the polymorphism at position 173 in combination with the mutation V386A on the activity of CYP11B2. Our in vitro findings show that the combination of the V386A mutation with the variant CYP11B2 173^Arg only slightly reduces the 18-hydroxylase and 18-oxidase activity, whereas the V386A mutation with the CYP11B2 173^Lys variant almost abolishes the 18-hydroxylation and 18-oxidation. In both cases the 11-hydroxylase activity is not affected. These findings highlight the importance of the genetic background of an enzyme when regarding the effect of clinical mutations.

An experimental examination of interindividual variation in feather corticosterone content in the house sparrow, Passer domesticus in southeast Australia

Non-invasive techniques for measuring glucocorticoids (GCs) have become more prevalent, due to the advantage of eliminating the effects of animal disturbance on GC levels and their potential to provide an integrated, historic estimate of circulating GC levels. In the case of birds, corticosterone (CORT) is deposited in feathers, and may reflect a bird's GC status over the period of feather synthesis. This technique thus permits a retrospective view of the average circulating GC levels during the moult period. While it is generally assumed that differences in feather CORT content (CORT_f) between individuals reflects their different stress histories during either natural or induced moult, it is not clear how much of this variation is due to extrinsic versus intrinsic factors. We examined this question by determining CORT_f in free-living house sparrows (Passer domesticus) from two populations, one urban and the other rural, that were plucked before and after exposure to different plasma CORT levels while held captive. We experimentally manipulated plasma CORT by implanting birds with either a corticosterone-filled, metyrapone-filled, or empty ('sham') silastic capsule as replacement feathers first emerged. The pattern of post-treatment CORT_f was consistent with our expectations, based on plasma CORT levels of an experimentally implanted reference group. However, there was no statistically significant difference in CORT_f between these treatment groups unless sex, population origin, and CORT_f of original feathers for each individual were included in a model. Thus, birds with higher CORT_f in feathers removed for this experiment tended to have higher CORT_f in post-treatment replacement feathers, irrespective of treatment. In addition, we found that feather fault bar scores were significantly higher in CORT-treated birds than in the other two treatment groups, but did not vary directly with CORT_f level. Our study therefore broadly confirms the use of feathers as a non-invasive tool to estimate plasma CORT during moult in birds, but importantly demonstrates the potential for intrinsic differences in stress characteristics between populations and individuals to obscure the effects extrinsic stressors might have on CORT_f.

Steroid 17-hydroxylase and 17,20-lyase deficiencies, genetic and pharmacologic

Steroid 17-hydroxylase 17,20-lyase (cytochrome P450c17, P450 17A1, CYP17A1) catalyzes two major reactions: steroid 17-hydroxylation followed by the 17,20-lyase reactions. The most severe mutations in the cognate CYP17A1 gene abrogate all activities and cause combined 17-hydroxylase/17,20-lyase deficiency (17OHD), a biochemical phenotype that is replicated by treatment with the potent CYP17A1 inhibitor abiraterone acetate. The adrenals of patients with 17OHD synthesize 11-deoxycorticosterone (DOC) and corticosterone but no 19-carbon steroids, similar to the rodent adrenal, and DOC causes hypertension and hypokalemia. Loss of 17,20-lyase activity precludes sex steroid synthesis and leads to sexual infantilism. Rare missense CYP17A1 mutations minimally disrupt 17-hydroxylase activity but cause isolated 17,20-lyase deficiency (ILD), Mutations in the POR gene encoding the required cofactor protein cytochrome P450-oxidoreductase causes a spectrum of disease from ILD to 17OHD combined with 21-hydroxylase and aromatase deficiencies, sometimes including skeletal malformations. Mutations in the CYB5A gene encoding a second cofactor protein cytochrome b₅ also selectively disrupt 17,20-lyase activity and cause the purest form of ILD. The clinical manifestations of these conditions are best understood in the context of the biochemistry of CYP17A1.

Corticosterone metabolites originating as a consequence of solvated electron (e(-)aq) emission

Corticosterone in water-ethanol solution can eject "solvated electrons" (eaq(-)) when excited into the singlet state by monochromatic UV-light (λ=254 nm). As a consequence of this process free radicals and H(+) ions were also generated. Hence, the objectives of this study were to determine the quantum yield, Q, at different corticosterone concentrations, and elucidate the fate of the generated free radicals and the involved reaction mechanisms. Because of the formation of associates, which consume a part of the emitted eaq(-), the Q decrease with increase of cortisone concentration. Additionally the H(+) ions scavenge and convert a part of the ejected eaq(-) into H-atoms. In comparsion with progesterone, the Q of corticosterone is much higher. Evidently, this effect is due to the two OH groups of corticosterone, which act as intense emission centres for eaq(-). Thereby, the generated free radicals from corticosterone lead to formation of metabolites, which were analyzed by combination of liquid-chromatography with mass spectrometry (LC/MS) method. Two of them were identified: 5α-pregnan-3α, 21-diol-11, 20-dione and 20β-dihydroxycortisone. Both have the same mass number of 348.230. To explain the involved, rather complicated processes, a probable reaction mechanism is suggested.

Determinants of parental care and offspring survival during the post-fledging period: males care more in a species with partially reversed sex roles

Sexual conflict is magnified during the post-fledging period of birds when the sexes face different trade-offs between continuing parental care or investing in self maintenance or other mating opportunities. Species with reversed sex roles provide a unique opportunity to study the relationship between mating systems and investment in parental care. Here, we provide the first detailed study of the length of care by males versus females (n = 24 pairs) during the post-fledging period, assessing factors that may promote care within and between the sexes. In the northern flicker Colaptes auratus, a species with partly reversed sex roles, males cared longer than females (average 16 versus 12 days, respectively). Overall, 36% of females but no males deserted the brood prior to fledgling independence. Parents that provisioned nestlings at a high rate also spent more days feeding fledglings. Among males, age and nestling feeding rates were positively associated with the length of care. Among females, a low level of feather corticosterone (CORTf) was associated with a longer length of care. About 45% of fledglings died within the first week, but fledglings with intermediate body mass had the highest survival suggesting stabilizing selection on mass. Fledgling survival was also higher in individuals with larger broods and lower levels of CORTf. We demonstrate that because females can be polyandrous they often desert the brood before males, and that the sexes respond to different cues relating to their energy balance when deciding the length of care given to their offspring.

Are motorways potential stressors of roadside wood mice (Apodemus sylvaticus) populations?

Linear infrastructures represent one of the most important human impacts on natural habitats and exert several effects on mammal populations. Motorways are recognized as a major cause of habitat fragmentation and degradation and of biodiversity loss. However, it is unknown whether motorways lead to increased physiological stress reactions in wild animal populations. We analysed faecal corticosterone metabolites (FCM) in wild populations of wood mice (Apodemus sylvaticus) living in a well-preserved Mediterranean agro-pastoral woodland at different distances (verge, 500 m and 1000 m) from the AP-51 motorway in Spain. Wood mice were captured with Sherman live traps, and fresh faecal samples from 424 individuals were collected and analyzed in the laboratory. The quantification of FCM was performed by a 5α-pregnane-3β,11β, 21-triol-20-one enzyme immunoassay. Results showed that females had higher FCM levels than males, and these levels were higher in breeding females. In addition, FCM levels were positively correlated with body weight of individuals. Wood mice captured where cattle were present showed higher FCM levels than individuals living where cattle were not detected. FCM levels were higher in non-breeding individuals living close to the motorway compared with FCM levels in those individuals captured further from the motorway. This is the first study showing evidence of the motorways' impact on physiological stress reactions in wild wood mice populations. Understanding how free-living animals are influenced by human interventions could help to understand other subtle changes observed in wild animal populations. Since mice are used world-wide as research models these results could open new perspectives testing human influence on the natural environment and trade-offs of species in degraded ecosystems.

An alternative explanation of hypertension associated with 17α-hydroxylase deficiency syndrome

The syndrome of 17α-hydroxylase deficiency is due to the inability to synthesize cortisol and is associated with enhanced secretion of both corticosterone and 11-deoxy-corticosterone (DOC). In humans, corticosterone and its 5α-Ring A-reduced metabolites are excreted via the bile into the intestine and transformed by anaerobic bacteria to 21-dehydroxylated products: 11β-OH-progesterone or 11β-OH-(allo)-5α-preganolones (potent inhibitors of 11β-HSD2 and 11β-HSD1 dehydrogenase). Neomycin blocks the formation of these steroid metabolites and can blunt the hypertension in rats induced by either ACTH or corticosterone. 3α,5α-Tetrahydro-corticosterone, 11β-hydroxy-progesterone, and 3α,5α-tetrahydro-11β-hydroxy-progesterone strongly inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase activity; all these compounds are hypertensinogenic when infused in adrenally intact rats. Urine obtained from a patient with 17α-hydroxylase deficiency demonstrated markedly elevated levels of endogenous glycyrrhetinic acid-like factors (GALFs) that inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase activity (>300 times greater, and >400 times greater, respectively, than those in normotensive controls). Thus, in addition to DOC, corticosterone and its 5α-pathway products as well as the 11-oxygenated progesterone derivatives may play a previously unrecognized role in the increased Na(+) retention and BP associated with patients with 17α-hydroxylase deficiency.

Ligand structural motifs can decouple glucocorticoid receptor transcriptional activation from target promoter occupancy

Glucocorticoid (GC) induction of the tyrosine aminotransferase (TAT) gene by the glucocorticoid receptor (GR) is a classic model used to investigate steroid-regulated gene expression. Classic studies analyzing GC-induction of the TAT gene demonstrated that despite having very high affinity for GR, some steroids cannot induce maximal TAT enzyme activity, but the molecular basis for this phenomenon is unknown. Here, we used RT-PCR and chromatin immunoprecipitation to determine TAT mRNA accumulation and GR recruitment to the TAT promoter (TAT-GRE) in rat hepatoma cells induced by seven GR ligands: dexamethasone (DEX), cortisol (CRT), corticosterone (CCS), 11-deoxycorticosterone (DOC), aldosterone (ALD), progesterone (PRG) and 17-hydroxyprogesterone (17P). As expected, DEX, CRT, CCS and ALD all induced both TAT mRNA and GR recruitment to the TAT-GRE, while PRG and 17P did not. However, while DOC could not induce significant TAT mRNA, it did induce robust GR occupancy of the TAT-GRE. DOC also induced recruitment of the histone acetyltransferase p300 to the TAT-GRE as efficiently as DEX. These DOC-induced effects recapitulated at another GR target gene (sulfonyltransferase 1A1), and DOC also failed to promote the multiple changes in gene expression required for glucocorticoid-dependent 3T3-L1 adipocyte differentiation. Structural simulations and protease sensitivity assays suggest that DOC and DEX induce different conformations in GR. Thus, although steroids that bind GR with high affinity can induce GR and p300 occupancy of target promoters, they may not induce a conformation of GR capable of activating transcription.

Stress coping styles and singing behavior in the short-tailed singing mouse (Scotinomys teguina)

Stress coping styles have been characterized as a proactive/reactive dichotomy in laboratory and domesticated animals. In this study, we examined the prevalence of proactive/reactive stress coping styles in wild-caught short-tailed singing mice (Scotinomys teguina). We compared stress responses to spontaneous singing, a social and reproductive behavior that characterizes this species. To establish proactive/reactive profiles for singing mice, we measured exploratory and anxiety behavior using an open-field behavioral test. We examined correlations between open-field behaviors and fecal corticosterone (CORT) metabolites, baseline plasma CORT, and stress-induced CORT. Mice with proactive behavioral responses in the open-field had higher fecal CORT titers than reactive males, but did not differ in baseline or stress-induced plasma CORT. We suggest that individual differences in CORT metabolism may contribute to this surprising pattern. Males that sang in the open-field were behaviorally proactive and had lower stress-induced CORT, indicating a link between stress responses and singing in this species. Overall, the data demonstrate that singing mice offer an interesting model for exploring how stress reactivity can shape social behaviors.

Hexose-6-phosphate dehydrogenase modulates the effect of inhibitors and alternative substrates of 11beta-hydroxysteroid dehydrogenase 1

Intracellular glucocorticoid reactivation is catalyzed by 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1), which functions predominantly as a reductase in cells expressing hexose-6-phosphate dehydrogenase (H6PDH). We recently showed that the ratios of cortisone to cortisol and 7-keto- to 7-hydroxy-neurosteroids are regulated by 11beta-HSD1 and very much depend on coexpression with H6PDH, providing cosubstrate NADPH. Here, we investigated the impact of H6PDH on the modulation of 11beta-HSD1-dependent interconversion of cortisone and cortisol by inhibitors and alternative substrates. Using HEK-293 cells expressing 11beta-HSD1 or coexpressing 11beta-HSD1 and H6PDH, we observed significant differences of 11beta-HSD1 inhibition by natural and pharmaceutical compounds as well as endogenous hormone metabolites. Furthermore, we show potent and dose-dependent inhibition of 11beta-HSD1 by 7-keto-DHEA in differentiated human THP-1 macrophages and in HEK-293 cells overexpressing 11beta-HSD1 with or without H6PDH. In contrast, 7-ketocholesterol (7-KC) did not inhibit 11beta-HSD1 in HEK-293 cells, even in the presence of H6PDH, but inhibited 11beta-HSD1 reductase activity in differentiated THP-1 macrophages (IC(50) 8.1+/-0.9microM). 7-Keto-DHEA but not 7-KC inhibited 11beta-HSD1 in HEK-293 cell lysates. In conclusion, cellular factors such as H6PDH can significantly modulate the effect of inhibitors and alternative 7-oxygenated substrates on intracellular glucocorticoid availability.

The corticosteroid metabolic profile of the mouse

Data are presented on the urinary corticosteroid metabolic profile of the mouse strain 129/svJ. Through the use of GC/MS we have characterized, or tentatively identified corticosterone (Kendall's compound B) metabolites of both the 11beta-hydroxy and 11-carbonyl (compound A) series in urine. Full mass spectra of the methyloxime-trimethylether derivatives of 15 metabolites are included in the paper as an aid to other researchers in the field. Metabolites ranged in polarity from tetrahydrocorticosterone (THB) to dihydroxy-corticosterone with dominance of highly polar steroids. We found that prior to excretion corticosterone can undergo oxidation at position 11beta, reduction at position 20 and A-ring reduction. Metabolites retaining the 3-oxo-4-ene structure can be hydroxylated at position 6beta- as well as at an unidentified position, probably 16alpha-. Saturated steroids can be hydroxylated at positions 1beta-, 6alpha-, 15alpha- and 16alpha. A pair of hydroxy-20-dihydro-corticosterone metabolites (OH-DHB) were the most important excretory products accounting for about 40% of the total. One metabolite of this type was identified as 6beta-hydroxy-DHB; the other, of similar quantitative importance was probably 16alpha-hydroxy-DHB. The ratio of metabolites of corticosterone (B) to those of 11-dehydro-corticosterone (A) was greater than 9:1, considerably higher than that for the equivalent "human" ratio of 1:1 for cortisol to cortisone metabolites. Results from this study allowed the evaluation of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) activity in mice with deleted glucose-6-phosphate transporter (G6PT). These mice had attenuated back-conversion of A to B resulting in an increased ratio of A-metabolites to B-metabolites [Walker EA, Ahmed A, Lavery GG, Tomlinson JW, Kim SY, Cooper MS, Stewart PM, 11beta-Hydroxysteroid dehydrogenase type 1 regulation by intracellular glucose-6-phosphate, provides evidence for a novel link between glucose metabolism and HPA axis function. J Biol Chem 2007;282:27030-6]. We believe this study is currently the most comprehensive on the urinary steroid metabolic profile of the mouse. Quantitatively less steroid is excreted in urine than in feces by this species but urine analysis is more straightforward and the hepatic metabolites are less subject to microbial degradation than if feces was analyzed.

Lack of interference of common phytoecdysteroids with production of nitric oxide by immune-activated mammalian macrophages

Effects of selected common phytoecdysteroids on immunobiological responses triggered by lipopolysaccharide and interferon-gamma (IFN-gamma) were tested under in vitro conditions using murine resident peritoneal macrophages. Namely, production of nitric oxide was investigated. The series of test agents encompassed ecdysteroids occurring often as major components of the ecdysteroid fraction in numerous plant extracts: 20-hydroxyecdysone (20E), polypodine B, ajugasterone C, ponasterone A and inokosterone. Their structural variability concerns only variation in the number and position of hydroxyls. Two additional side-chain modified ecdysteroids: makisterone A (with a methyl substituent at position 24) and carthamosterone (with a cyclic side-chain lactone), and three ecdysteroid analogs: poststerone, rubrosterone and dihydrorubrosterone (devoid of side chains) were included into the test series. All test compounds, except of ponasterone A, represent natural substances isolated from the medicinal plant Leuzea carthamoides and are supposed to be significant for the often reported pharmacological activities of preparations derived from this species. However, the tested ecdysteroids did not interfere with the immunobiological activity of the immunocompetent cells. Our results thus differ from the so far reported information.

Comparison of the effects of chemical permeation enhancers on the lipoidal pathways of human epidermal membrane and hairless mouse skin and the mechanism of enhancer action

Previously, the effects of chemical permeation enhancers upon the permeability of the lipoidal pathway of hairless mouse skin (HMS) were investigated and a quantitative structure enhancement relationship was established. The present study was to study the effects of these enhancers on human epidermal membrane (HEM) using the same experimental method employed in the previous HMS studies. The effects of enhancers on the permeability coefficients of the lipoidal pathways of HEM and HMS for corticosterone were found to be essentially the same. In the equilibrium uptake studies of the enhancers and beta-estradiol, it was found that the amounts of enhancers taken up and the partitioning of beta-estradiol into the HEM stratum corneum (SC) intercellular lipid under the E = 10 conditions were different from those of HMS. Despite these differences, the HEM data show a correlation between the intercellular lipid/PBS partition coefficients of the enhancers and the enhancer n-octanol/PBS partition coefficients. This correlation is consistent with the observed chemical microenvironment of the site of enhancer action in the HMS SC in previous studies. Therefore, provided with proper experimental protocols, HMS can be a reliable model for the evaluation of the effects of skin permeation enhancers on the lipoidal pathway of HEM.

Studies on neurosteroids XXIII. Analysis of tetrahydrocorticosterone isomers in the brain of rats exposed to immobilization using LC-MS

The identification and quantification of tetrahydrocorticosterone isomers (THBs; 3alpha,5alpha-, 3beta,5alpha-, 3alpha,5beta- and 3beta,5beta-THB) in rat brains using liquid chromatography (LC)-mass spectrometry (MS) are described. For the identification, the THBs were converted to the atmospheric pressure chemical ionization (APCI)-active derivatives, i.e., the dinitrobezoyl esters and 2-nitro-4-trifluoromethylphenyl hydrazones, and detected in the negative-ion mode. These derivatives showed 60- and 40-fold higher sensitivities, respectively, than intact steroids measured in the positive-APCI-MS. The derivatized THBs were satisfactorily separated from the others during the reversed-phase LC. The THBs were not detected at all in the brains of the unstressed rats. When the rats were exposed to the immobilization for 20 min, 3alpha,5alpha- and 3beta,5alpha-THB were detected as the major metabolites together with small amounts of 3alpha,5beta- and 3beta,5beta-THB in the male rat brain, while only 3alpha,5alpha-THB was detected in the female rats. Thus, the steroid variety found in the brains was different between the sexes. In the next step, 3alpha,5alpha-THB, a major metabolite found in the brains of the stressed rats, was quantified as its dinitrobezoyl ester. This method was accurate and reproducible, and the limit of quantitation was 1.0 ng/g tissue when a 50 mg tissue sample was used. There was also a sex difference in the brain 3alpha,5alpha-THB level; it was significantly higher in the female rats than in the male rats (P<0.05), although the brain corticosterone level was not higher in the stressed female rats than in the male rats (no statistical difference).

Quantification of dexamethasone and corticosterone in rat biofluids and fetal tissue using highly sensitive analytical methods: assay validation and application to a pharmacokinetic study

A sensitive, specific, accurate and precise LC/MS/MS method was developed for the simultaneous measurement of dexamethasone and corticosterone in rat plasma. The method was extended to dexamethasone analysis in rat plasma ultrafiltrate and fetal tissues. Samples were processed using SPE involving Oasis HLB cartridges, which offered complete extraction recovery for the analytes. Samples were subsequently analyzed using LC/MS/MS. A structurally related corticosteroid, prednisolone, was used as the internal standard. Using a 500 microL plasma sample, limits of quantification of 0.2 and 2.0 ng/mL were achievable for dexamethasone and corticosterone. This level of sensitivity allowed characterization of maternal/fetal dexamethasone profiles after administration of multiple doses of dexamethasone sodium phosphate to rats. However, this sensitivity was not satisfactory for corticosterone during pharmacokinetic studies involving dexamethasone due to its strong adrenosuppressive effect. This led us to investigate the suitability of a commercially available radioimmunoassay kit, which through extensive testing and minor modifications was found to offer extremely sensitive, specific, accurate and precise analysis of corticosterone. Knowledge of the steroid profiles captured using these highly sensitive analytical tools may potentially help in the optimization of corticosteroid therapy during pregnancy.

Towards a correlation between drug properties and in vitro transdermal flux variability

Over recent years, there has been growing evidence that the permeability coefficient variability describing any specific transdermal drug delivery system is not always normally distributed. However, since different researchers have used different test compounds, methodologies and skin types, it has been difficult to identify any general correlation between drug properties and flux variability. The aim of the present study was to investigate whether there was a relationship between these two variables. To this end, six different compounds (sucrose, adenosine, aldosterone, corticosterone, oestradiol and testosterone) exhibiting a range of partition coefficients but relatively similar molecular weights were screened by taking multiple replicate measurements of their permeation profiles as they penetrated across porcine skin in vitro. It was found that for relatively hydrophilic solutes (log P(o/w)< or = approximately 2.5), physicochemical properties that facilitated slow transdermal flux were associated with more positively skewed permeability coefficient distributions while rapid flux was associated with more symmetric distributions. However, no correlation could be found between molecular properties and the extent of statistical fit to either the normal or log-normal distribution.

Effect of drug type on the degradation rate of PLGA matrices

We compare the rate of drug release through the degradation of 50:50 polylactic-co-glycolic acid polymer pellets, for six different drugs: Thiothixene, Haloperidol, Hydrochlorothiozide, Corticosterone, Ibuprofen, and Aspirin. Despite using the same polymer matrix and drug loading (20% by weight), we find that the rate of polymer degradation and the drug release profile differ significantly between the drugs. We conclude that the design of biodegradable polymeric drug carriers with high drug loadings must account for the effect of the drug on the polymer degradation and drug release rate.

Faecal corticosterone concentrations indicate that separately housed male mice are not more stressed than group housed males

Mice account for over 80% of all animals used in experimentation. This study investigated how different housing conditions affected stress levels by measuring both corticosterone levels, using non-invasive faecal collection, and behaviour. Sixty outbred MF1 male mice were used which were separated into five different housing conditions at the beginning of the study, (A) individually housed, floor area 490 cm(2) per individual, (B) groups of three mice, floor area 163 cm(2) per individual, (C) groups of three mice, floor area 320 cm(2) per individual, (D) groups of six mice, floor area 160 cm(2) per individual, (E) groups of six mice, floor area 230 cm(2) with extra height per individual to allow visual contact. Mice in all housing conditions were provided with a basic enrichment of paper bedding and a plastic house. The results from this study showed that singly housed mice reduced their corticosterone levels over time after separation reaching a minimum from 14 days onwards. Groups of 6 mice housed together showed no difference over time. Also there was no significant difference in corticosterone levels between the different housing densities, with no differences for aggression or stereotypical behaviour suggesting that there is no ideal group density for this strain and sex of mouse. Providing additional enrichment to the cages caused a significant decrease in corticosterone levels for group housed mice, but individually housed mice remained unaffected by increasing their enrichment level. They spent significantly more time sleeping in the enhanced cage but without any reduction in stereotypical behaviour. For group housed mice, additional enrichment should be mandatory to reduce stress levels and therefore increase their welfare standards, while singly housed mice required only basic levels of enrichment and should be separated from their group for a minimum of 2 weeks before measurements are taken.

Crystal structure of murine 11 beta-hydroxysteroid dehydrogenase 1: an important therapeutic target for diabetes

11Beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) catalyzes the conversion of 11-dehydrocorticosterone to its active form corticosterone in rodents (or cortisone to cortisol in humans). The reductive reaction of the 11-keto to 11-hydroxyl is the pivotal switch in the activation of glucocorticoids. An excess of active glucocorticoids has been shown to play a key role in metabolic disorders such as diabetes and obesity. Therefore, 11beta-HSD1 represents an important therapeutic target for the treatment of these diseases. To facilitate the iterative design of inhibitors, we have crystallized and determined the three-dimensional structures of a binary complex of murine 11beta-HSD1 with NADP(H) to a resolution of 2.3 A and of a ternary complex with corticosterone and NADP(H) to a resolution of 3.0 A by X-ray crystallography. The enzyme forms a homodimer in the crystal and has a fold similar to those of other members of the family of short chain steroid dehydrogenases/reductases (SDRs). The structure shows a novel folding feature at the C-terminus of the enzyme. The C-terminal helix insertions provide additional dimer contacts, exert an influence on the conformations of the substrate binding loops, and present hydrophobic regions for potential membrane attachment. The structure also reveals how 11beta-HSD1 achieves its selectivity for its substrate.

Molecular surface point environments for virtual screening and the elucidation of binding patterns (MOLPRINT 3D)

A novel method (MOLPRINT 3D) for virtual screening and the elucidation of ligand-receptor binding patterns is introduced that is based on environments of molecular surface points. The descriptor uses points relative to the molecular coordinates, thus it is translationally and rotationally invariant. Due to its local nature, conformational variations cause only minor changes in the descriptor. If surface point environments are combined with the Tanimoto coefficient and applied to virtual screening, they achieve retrieval rates comparable to that of two-dimensional (2D) fingerprints. The identification of active structures with minimal 2D similarity ("scaffold hopping") is facilitated. In combination with information-gain-based feature selection and a naive Bayesian classifier, information from multiple molecules can be combined and classification performance can be improved. Selected features are consistent with experimentally determined binding patterns. Examples are given for angiotensin-converting enzyme inhibitors, 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, and thromboxane A2 antagonists.

Models of Steroid Binding Based on the Minimum Deviation of Structurally Assigned 13C NMR Spectra Analysis (MiDSASA)

This paper develops a quantitative k-nearest neighbors modeling technique. The technique is used to demonstrate that a compound's biological binding activity to a receptor can be calculated from the minimum of the square root of the sum of squared deviations (SSSD) of a structurally assigned chemical shift on a template between the unknown compound to be predicted and a set of known compounds with known activities. When building models of biological activity, nonlinear relationships are built into the input training data. If a model is developed by selecting only compounds with minimum structurally assigned chemical shift deviations from the unknown compound, some of the nonlinear relationships can be removed. The smaller the total chemical shift deviation between a compound with known activity and another compound with unknown activity, the more likely it will have similar biological, chemical, and physical properties. This means that a model can be produced without rigorous statistics or neural networks. This technique is similar to structure-activity relationship (SAR) modeling, but instead of relying on substructure fragments to produce a model, this new model is based on minimum chemical shift differences on those substructure fragments. We refer to this method as minimum deviation of structurally assigned spectra analysis (MiDSASA) modeling. Modeling by the minimum deviation concept can be applied to other chemoinformatic data analyses such as metabolite concentrations in metabolic pathways for metabolomics research. A MiDSASA template model for 30 steroids binding the corticosterone binding globulin based on the activity factors of the two nearest compounds had a correlation of 0.88. A MiDSASA template model for 50 steroids binding the aromatse enzyme based on the average activity of the four nearest compounds had a correlation of 0.71.

Mechanistic studies of the effect of hydroxypropyl-beta-cyclodextrin on in vitro transdermal permeation of corticosterone through hairless mouse skin

Literature reports reveal that the issue of whether cyclodextrins may act as skin permeation enhancers has not been resolved. Accordingly, in vitro skin transport studies were conducted to address this question. Corticosterone (3H-CS and/or non-radiolabeled CS) was chosen as the model permeant for transport experiments with hairless mouse skin (HMS) and with a synthetic cellulose membrane of 500 molecular weight cut off (MWCO), the latter to help establish baseline behavior. Hydroxypropyl-beta-cyclodextrin (HPbetaCD) was selected as the representative cyclodextrin. The CS/HPbetaCD complexation constant was determined both from solubility data (saturation conditions) in phosphate buffered saline (PBS), pH 7.4 and with data obtained from PBS/silicone polymer partitioning experiments, the latter experiments permitting the determination of the complexation constant at low CS concentrations. These results were used in the calculations of the free CS concentrations in the donor chamber of the transport experiments. The CS transport experiments were conducted at CS solubility saturation and under supersaturation (resulting from autoclaving at 121 degrees C) conditions as well at very low (tracer level) concentrations. The effect of polyvinylpyrrolidone as a solution additive was also evaluated. The following were the key outcomes of this study. Contrary to literature reports, there was no evidence that HPbetaCD is an enhancer for CS transport through HMS. The CS permeability coefficient values obtained with HMS in all of the experiments were found to be the same within experimental error when calculated on the basis of the free CS concentration as the driving force for permeation. The constancy of the permeability coefficient in the presence and absence of HPbetaCD is interpreted to mean that, in these experiments, HPbetaCD did not alter the barrier properties of HMS stratum corneum to any significant extent nor did it enhance CS transport in any other manner such as by a carrier mechanism involving the aqueous boundary layer or by a carrier mechanism within the stratum corneum.

Penetration of endogenous steroid hormones corticosterone, cortisol, aldosterone and progesterone into the brain is enhanced in mice deficient for both mdr1a and mdr1b P-glycoproteins

Numerous investigations have confirmed an important role for multidrug-resistance gene 1-type P-glycoproteins (MDR1-type P-gps) in the blood-brain barrier, protecting the brain against the accumulation of a wide range of toxic xenobiotics and drugs. Several studies have provided evidence in vitro that certain steroid hormones are transported by MDR1-type P-gps; however, the question of whether this might also apply to the situation in vivo still remained to be determined. We used mice deficient for both murine mdr1a and mdr1b P-gps [mdr1a/1b(-/-)] to determine the uptake of [3H]-cortisol, [3H]-corticosterone, [3H]-aldosterone and [3H]-progesterone into the plasma, brain, testes, liver, spleen, pituitary and adrenal glands. We provide evidence that the access of the endogenous steroid hormones corticosterone, cortisol and aldosterone is regulated by MDR1-type P-gps in vivo. As peripherally administered steroid hormones accumulate in the brain of mice deficient for MDR1-type P-gps, mdr1a/1b proteins are likely to transport these hormones out of the brain, providing a kinetic barrier to their entry. Intracerebral progesterone concentrations are influenced by MDR1-type P-gp function as well; however, the effects are only small. In addition, all four endogenous glucocorticoid hormones accumulated in the testes of mdr1a/1b(-/-) mice. Our findings underline the importance of MDR1-type P-gps as an endogenous barrier system controlling the access of endogenous steroid hormones at the blood-brain barrier to maintain homeostatic control and to protect central nervous system neurones.

Substrate specificity of human 3(20)alpha-hydroxysteroid dehydrogenase for neurosteroids and its inhibition by benzodiazepines

In this report, we compared kinetic constants and products in the reduction of the neurosteroids, 3alpha,5alpha-tetrahydroprogesterone (3alpha,5alpha THP) and 3alpha,5alpha-tetrahydrodeoxycorticosterone (3alpha,5alpha-THDOC), and their precursors, 5alpha-dihydroprogesterone (5alpha-DHP), 5alpha-dihydrodeoxycorticosterone (5alpha-DHDOC) and progesterone, by three isoenzymes (AKR1C1, AKR1C2 and AKR1C3) of human 3alpha-hydroxysteroid dehydrogenase. AKR1C1 efficiently reduced 3alpha,5alpha-THP, 5alpha-DHP and progesterone to their 20alpha-hydroxy metabolites, and slowly converted 5alpha-DHDOC to 3alpha,5alpha-THDOC. AKR1C2 exhibited low 20-ketoreductase activity for 3alpha,5alpha-THP and moderate 3-ketoreductase activity for 5alpha-DHP and 5alpha-DHDOC. 3alpha,5alpha-THDOC was not reduced by the two isoenzymes. No significant activity for the steroids was detected with AKR1C3. The results suggest that AKR1C2 is involved in the neurosteroid synthesis, but AKR1C1 decreases the neurosteroid concentrations in human brain by inactivating 3alpha,5alpha-THP and eliminating the precursors from the synthetic pathways. In addition, we found that the several benzodiazepines inhibited the three isoenzymes noncompetitively with respect to the substrate. Although cloxazolam was a potent and specific inhibitor of AKR1C3, diazepam, estazolam, flunitrazepam, medazepam and nitrazepam, that inhibited AKR1C1 and AKR1C2, may influence the neurosteroid metabolism.

Homology modelling of the ligand-binding domain of glucocorticoid receptor: binding site interactions with cortisol and corticosterone

Glucocorticoids are involved in the growth, development and homeostasis of a number of tissues. The physiological effects of this class of lipophilic steroids are mediated by ligand-inducible nuclear transcription factor, the glucocorticoid receptor/mineralocorticoid receptor, a member of the steroid/nuclear receptor superfamily. The glucocorticoid receptor interacts specifically with glucocorticoids, whereas the mineralocorticoid receptor interacts with both glucocorticoids and mineralocorticoids. The molecular structure of progesterone complexed to its receptor obtained from X-ray crystal structure analysis is used to build up a homology model of mouse glucocorticoid receptor ligand-binding domain (mGR LBD). The secondary structure of mGR LBD contains 11 helices, nine turns and four sheets. The mGR LBD contains a long helix, H9, with 30 residues, and exhibits slight deformation when the receptor protein binds with its cognate ligands. The mGR LBD has a 12-residue C-terminal extension (residues 772-783) that is essential for hormone binding. This extension is tightly fixed in position by an antiparallel beta-sheet interaction between amino acids 680-682 (S3) and 775-777 (S4). The three-dimensional model reveals two polar sites located at the extremities of the elongated hydrophobic ligand-binding pocket. Cortisol and corticosterone are docked to this ligand-binding pocket. The difference accessible surface area study revealed the steroid-binding region of mGR LBD.

18-Vinyldeoxycorticosterone: a potent inhibitor of the bovine cytochrome P-450(11) beta

18-Vinylprogesterone (18-VP) and 18-ethynylprogesterone (18-EP) have proved to be potent suicide inhibitors of P-450(11) beta, the last enzyme of aldosterone biosynthesis (Delorme, C.; Piffeteau, A.; Viger, A.; Marquet, A. Eur. J. Biochem. 1995, 232, 247; Delorme, C.; Piffeteau, A.; Sobrio, F.; Marquet, A. Eur. J. Biochem. 1997, 248, 252). This paper describes the synthesis of 18-vinyldeoxycorticosterone (18-VDOC), an analogue of deoxycorticosterone (DOC), the physiological substrate of the enzyme, and the evaluation of its reversible inhibiting properties for deoxycorticosterone and corticosterone oxidation by the bovine enzyme. 18-VDOC has been obtained by hydroxylation at C-21 of a 18-VP precursor. Its reversible Ki values are, respectively, 0.3 microM for the 11 beta-hydroxylation and 0.8 microM for the 18-hydroxylation. Hence, 18-VDOC is the strongest competitive inhibitor of bovine P-450(11) beta described so far, but in contrast with 18-VP, it does not inhibit more efficiently the 18-hydroxylation than the 11-hydroxylation.

11 beta-Hydroxysteroid dehydrogenase enzyme activity in granulosa cells derived from ovarian follicles of in vitro fertilization patients

11 beta-Hydroxysteroid dehydrogenase (HSD) activity was measured in freshly frozen granulosa cells isolated from follicles of twenty-one infertility patients undergoing in vitro fertilization-embryo transfer (IVF-ET). A total of 213 follicles were analyzed for 11 beta-HSD activity. Both nicotinamide-adenine dinucleotide (NAD) and nicotinamide-adenine dinucleotide phosphate (NADP) dependent 11 beta-dehydrogenase activities were measured in granulosa cells. The activity in reductive direction (11-oxoreductase activity) was not measurable either with NADH or NADPH as cofactors. NAD- and NADP-dependent dehydrogenase activities are in comparable levels at 100 nmol/l and 1 mumol/l corticosteroid concentrations. For comparing enzyme activities of individual follicles, significant enzyme activity was considered to be a level of > 2 nmol/l/min/mg. 41.3% of the follicles demonstrated enzyme activity, 58.7% did not. The mean 11 beta-dehydrogenase (11 beta-DH) activity was calculated for each patient. Those patients with levels > 2 nmol/l/min/mg were considered enzyme positive; those with mean levels < 2 nmol/l/min/mg were considered negative. No significant association was noted between follicle size, oocyte maturity or fertilization rates and 11 beta-DH activity. This study noted the presence of 11 beta-DH activity in granulosa cells, however, no association with oocyte maturity and fertilization was found.

Membrane-mediated inhibition of corticosterone on the release of arginine vasopressin from rat hypothalamic slices

The arginine vasopressin (AVP) released from the hypothalamic slices containing paraventricular and supraoptic nuclei of Sprague-Dawley rats sectioned with vibratome and incubated in static microchambers was measured by radioimmunoassay. The effect of bovine serum albumin-conjugated corticosterone (B-BSA) on the AVP release was investigated. The results were as follows: (1) B-BSA, within 20 min, significantly inhibited AVP release in a dose-dependent manner from 10(-7) to 10(-4) mol/l. (2) RU38486 (10(-4)-10(-3) mol/l) could partially block the inhibitory effect of B-BSA although it by itself did not change the AVP release. (3) With the elevation of Ca2+ concentration in the incubation medium, the AVP release was increased and the inhibitory effect of B-BSA enhanced; while in the absence of Ca2+, the AVP release decreased and the effect of B-BSA attenuated. (4) The inhibitory effect of B-BSA was enhanced in the presence of neomycin which itself had no influence on AVP release. These results indicated that the inhibitory effect of corticosterone is rapid and membrane-mediated which is non-genomic rather than classical genomic, and that the extracellular Ca2+ play a role in this rapid inhibitory effect.

The effect of temperature upon the permeation of polar and ionic solutes through human epidermal membrane

The temperature dependence of in vitro permeation through human epidermal membrane (HEM) was determined for urea, mannitol, tetraethylammonium ion (TEA), and corticosterone. The effect of temperature upon HEM electrical resistance was also measured. The majority of the experiments involved measuring the permeability coefficients of a specific permeant at 27 degrees C and 39 degrees C for a given HEM sample, the electrical resistance was also measured at each temperature. Similar experiments were also conducted with a model synthetic porous membrane. The effect of temperature was quantitated as the ratio of the permeability at 39 degrees C to the permeability at 27 degrees C for each permeant. These ratios observed for HEM with urea, mannitol, and TEA as the permeants were 1.66 +/- 0.05, 1.76 +/- 0.14, and 1.71 +/- 0.11, respectively. The change in temperature was shown to have a similar effect upon the electrical conductance of the HEM samples. The observed ratio for corticosterone permeation was 4.5 +/- 0.4. The experimental ratios observed for the three polar/ionic permeants were shown to approach those obtained from the model porous membrane and differed greatly from the ratio observed for the more lipophilic corticosterone, indicating differences in the effective transport mechanism/pathway for these classes of permeants. The permeability of urea was also observed to be inversely proportional to the electrical resistance of the HEM samples; this relationship was shown to be independent of temperature over the temperature range studied. The temperature dependence data and the observed relationship between urea permeability and electrical resistance strongly support the existence of a porous permeation pathway through the HEM as an operative diffusional route for polar-ionic permeants.

Identification of Trp-371 as the main site of specific photoaffinity labeling of corticosteroid binding globulin using delta 6 derivatives of cortisol, corticosterone, and progesterone as unsubstituted photoreagents

Immunopurified human corticosteroid binding globulin (CBG) was photolabeled with delta 6-[3H]cortisol, delta 6-[4-14C]cortisol, delta 6-[3H]corticosterone, and delta 6-[3H]progesterone. The maximal levels of specific incorporation, as estimated with tritiated photoreagents, were 0.21, 0.14, and 0.08 mol of label/mol of CBG, respectively. Tryptic cleavage of photolabeled CBG gave in all cases a major radioactive peptide that was no longer detectable when a 100-fold molar excess of cortisol was added to the photoreagents. Edman sequencing of tryptic peptides photolabeled with delta 6-[3H]cortisol or delta 6-[3H]corticosterone showed that these peptides correspond to residues 357-378 of the human CBG sequence. The major peak of radioactivity of these peptides was eluted at the 15th cycle (Trp-371). The radioactive tryptic peptides photolabeled with the four steroid photoreagents were subcleaved with alpha-chymotrypsin. The major part of radioactivity was recovered in the T-[*X]-S-S-L-F hexapeptide 370-375 (major peptide) and in the D-H-F-T-[*X]-S-S-L-F nonapeptide 367-375, at the second and fifth Edman cycles, respectively, whereas no PTH derivative could be identified at these cycles, thus suggesting Trp-371 as the main site of photolabeling for all tested photoreagents. Mass spectrometry of tryptic peptides photolabeled with delta 6-[3H]cortisol and delta 6-[3H]corticosterone and of chymotryptic peptides photolabeled with delta 6-[3H]cortisol, delta 6-[3H]corticosterone, and delta 6-[3H]progesterone showed molecular masses corresponding to the addition of delta 6-steroid photoreagents to the peptide.

Synthesis and identification of twelve A-ring reduced 6 alpha- and 6 beta-hydroxylated compounds derived from 11-deoxycortisol, corticosterone and 11-dehydrocorticosterone

The synthesis and identification of 12 A-ring reduced 6 alpha-(and 6 beta-)hydroxylated compounds derived from 11-deoxycortisol (S), corticosterone (B) and 11-dehydrocorticosterone (A) are reported here. These steroids were prepared in two steps from the corresponding 6 6 alpha-(and 6 beta-)hydroxy-4-pregnene-3-ones. Selective reduction of the 4,5 double bond yielded 12 6 alpha-(and 6 beta)hydroxy-5 alpha-(and 5 beta)pregnane-3,20-diones. Enzymatic reduction of these compounds with NADH and 3 alpha-hydroxysteroid dehydrogenase yielded the corresponding tetrahydro steroids. The steroids were characterized by high performance liquid chromatography (HPLC), gas chromatography mass spectrometry (GC and GC/MS) and in part by 1H-NMR. 6 beta OH-THS and 6 beta OH-5 alpha THS were identified by 1H-NMR. The structures of the two precursors, i.e. 6 beta OH-5 beta DHS and 6 beta OH-5 alpha DHS were confirmed by 1H-NMR using two-dimensional spectra. 6 alpha OH-THS was identified by comparing its HPLC, GC and MS data with those of the steroid obtained by enzymatic oxidation of the standard reference steroid 6 alpha OH-20 beta HHS to the corresponding 20-ketosteroid. The other steroids, e.g. 6 alpha OH-THB and 6 alpha OH-5 alpha THB were identified by using the proved sequence of elution of each of the epimer pairs on the normal phase HPLC column (5 alpha < 5 beta), and by the reversed order of elution of the same epimer pair as the methoxime-trimethylsilyl ethers on the GC column (5 alpha > 5 beta) and by the mass spectra, with the exception of 6 beta OH-THA.

Synthesis and characterization of the 6 alpha- and 6 beta-hydroxylated derivatives of corticosterone, 11-dehydrocorticosterone, and 11-deoxycortisol

This report describes the synthesis of 6 alpha, 17,21- and 6 beta, 17,21-trihydroxypregn-4-ene-3,20-dione, 6 alpha, 7,21- and 6 beta, 11 beta, 21-trihydroxypregn-4-ene-3,20-dione, and--for the first time--that of 6 alpha, 21- and 6 beta, 21-dihydroxypregn-4-ene-3,11,20-trione. The former four compounds were prepared by 6-hydroxylation of 17,21-trihydroxypregn-4-ene-3,20-dione and 11 beta, 21-dihydroxypregn-4-ene-3,20-dione, respectively. This was achieved by autoxidation or by oxidation with 3-chloroperbenzoic acid, of the 3-methoxy-pregna-3,5-dienes of the latter two steroids. The yield of the 6 beta-hydroxylated steroids, but not of their corresponding 6 alpha-epimers, was higher using autoxidation than the peracid. The two 6-hydroxylated pregnenetriones were prepared from 6 alpha, 21-diacetoxy-11 beta-hydroxypregn-4-ene-3,20-dione and 6 beta, 21-diacetoxy-11 beta-hydroxypregn-4-ene-3,20-dione, respectively, by oxidation with pyridinium chlorochromate. The above-mentioned six steroids were identified and characterized by nuclear magnetic resonance, infrared, ultraviolet, high performance liquid chromatography, gas chromatography, and mass spectrometry.

[The kinetic characteristics and stoichiometry of corticosterone interaction with cytosol receptors]

The interaction of molybdate-stabilised cytosol receptor of the rat brain and liver with corticosterone was studied in conditions of equilibrium and non-equilibrium in vitro. The hormone-receptors complexes with varying number of the receptor molecules were found to form consequentially. During their formation the complexes revealed the properties of disperse phases. The concentration of the receptors seems to be one of the regulating factors of activity of the complexes. An original experimental technique is described.

Steroidal fatty acid esters

Several years ago we discovered an unexpected family of steroidal metabolites, steroidal fatty acid esters. We found that fatty acid esters of 5-ene-3 beta-hydroxysteroids, pregnenolone and dehydroisoandrosterone are present in the adrenal. Subsequently, others have shown the existence of these non-polar 5-ene-3 beta-hydroxysteroidal esters in blood, brain and ovaries. Currently, almost every family of steroid hormone is known to occur in esterified form. We have studied the esters of the estrogens and glucocorticoids in some detail, and have found that these two steroidal families are esterified by separate enzymes. In a biosynthetic experiment performed simultaneously with estradiol and corticosterone, we established that the fatty acid composition of the steroidal esters is quite different. The corticoid is composed predominantly of one fatty acid, oleate, while the estradiol esters are extremely heterogeneous. Our studies have demonstrated that the estrogens are extremely long-lived hormones, that they are protected by the fatty acid from metabolism. They are extremely potent estrogens, with prolonged activity. Esterification appears to be the only form of metabolism that does not deactivate the biological effects of estradiol. We have demonstrated the biosynthesis of fatty acid esters of estriol, monoesters at both C-16 alpha and C-17 beta. They too are very potent estrogens. These fatty acid esters of the estrogens are the endogenous analogs of estrogen esters, like benzoate, cypionate, etc., which have been used for decades, pharmacologically because of their prolonged therapeutic potency. We have found that the estradiol esters are located predominantly in hydrophobic tissues, such as fat. Sequestered in these tissues, they are an obvious reservoir of estrogenic reserve, requiring only an esterase for activation. To the contrary the biological activity of the fatty acid esters of the glucocorticoid, corticosterone, is not different from that of its free parent steroid. We have shown that the rapid kinetics of its induction of gluconeogenic responses is caused by its labile C-21 ester which is rapidly hydrolyzed by esterase enzymes. While it appears that the physiological role of the estrogen esters may be related to their long-lived hormonal activity, the role of the other families of steroidal esters is not yet apparent. They, and perhaps the estrogen esters as well, must serve other purposes. Indeed they may serve important biological functions beyond those which we ordinarily associate with steroid hormones.