Clotting factor changes during the first cycle of oral contraceptive use.

OBJECTIVES: The risk of venous thromboembolism (VTE) is highest during the initial months of oral contraceptive (OC) use. We sought to evaluate the extent of hemostatic variable changes during the initial OC cycle and if such changes are related to systemic ethinyl estradiol (EE2) exposure. STUDY DESIGN: Participants provided multiple blood samples during a 21-day OC cycle (30mcg EE2; 150mcg levonorgestrel) and after a single dose following a washout period. Analytes included D-dimer, factor VIII activity, protein C total antigen and the hepatic proteins corticosteroid-binding globulin (CBG) and sex-hormone-binding globulin (SHBG). EE2 pharmacokinetic analyses related to the 24h after the first OC tablet (OC1) and at steady state (OC21). RESULTS: Seventeen women completed the study. D-dimer more than doubled by OC6 (p=.013) and remained elevated at OC21 (p=.012). D-dimer levels within women varied widely from day to day. Factor VIII increased 27% by OC2 (p<.001) but declined to a 9% increase by OC21. Protein C increased only 6%. EE2 steady-state area-under-the-curve ranged from 488 to 1103pg∙h/mL; higher levels were not correlated with greater increases in clotting variables. CBG and SHBG increased significantly but were not significantly correlated with levels of EE2 or with the hemostatic variables. CONCLUSIONS: D-dimer increases during the first OC cycle were at least as great as increases seen with longer OC use. These results provide support for the increased VTE risk during initial OC use. The extreme variability in D-dimer levels may be an important component of this risk. IMPLICATIONS: This study showed that increases in D-dimer are clearly evident in the first cycle of OC use and may be larger than are seen after a longer duration of use and thus provide biological support for the increased VTE risk during initial OC use found in epidemiological studies.

Bridging the Gap: The Potential Role of Corticosteroid Binding Globulin in Cardiac Steroid Facilitation.

Corticosteroid (glucocorticoids [GCs] and mineralcorticoids [MCs]) interact directly with cells of the cardiovascular system. Their signaling affects genomic and non-genomic receptors and comprises a multitude of alternative and interfering levels of interaction, which influence the physiological response. This review describes genomic and non-genomic pathways of steroid facilitation and portrays the current body of knowledge regarding corticosteroid-binding globulin (CBG). The latter is a carrier protein facilitating corticosteroid availability in the circulation and has recently been discovered intrinsically in cardiomyocytes. Thought experiments highlight potential areas of clinical research and hypotheses are presented for steroid- carrier interaction. Furthermore, this review comprises a conclusive overview of disease conditions and substances that influence CBG levels and summarizes the potential of CBG as a potential future biomarker.

Atom-based stochastic and non-stochastic 3D-chiral bilinear indices and their applications to central chirality codification.

Non-stochastic and stochastic 2D bilinear indices have been generalized to codify chemical structure information for chiral drugs, making use of a trigonometric 3D-chirality correction factor. In order to evaluate the effectiveness of this novel approach in drug design we have modeled the angiotensin-converting enzyme inhibitory activity of perindoprilate's sigma-stereoisomers combinatorial library. Two linear discriminant analysis models, using non-stochastic and stochastic linear indices, were obtained. The models had shown an accuracy of 95.65% for the training set and 100% for the external prediction set. Next the prediction of the sigma-receptor antagonists of chiral 3-(3-hydroxyphenyl)piperidines by multiple linear regression analysis was carried out. Two statistically significant QSAR models were obtained when non-stochastic (R(2)=0.953 and s=0.238) and stochastic (R(2)=0.961 and s=0.219) 3D-chiral bilinear indices were used. These models showed adequate predictive power (assessed by the leave-one-out cross-validation experiment) yielding values of q(2)=0.935 (s(cv)=0.259) and q(2)=0.946 (s(cv)=0.235), respectively. Finally, the prediction of the corticosteroid-binding globulin binding affinity of steroids set was performed. The obtained results are rather similar to most of the 3D-QSAR approaches reported so far. The validation of this method was achieved by comparison with previous reports applied to the same data set. The non-stochastic and stochastic 3D-chiral linear indices appear to provide a very interesting alternative to other more common 3D-QSAR descriptors.

QSAR study of steroid benchmark and dipeptides based on MEDV-13.

A molecular electronegativity distance vector based on 13 atomic types, called MEDV-13, is a descriptor for predicting the biological activities of molecules based on the quantitative structure-activity relations (QSAR). The MEDV-13 uses a modified electrotopological state (E-state) index to substitute for the relative eletronegativity (q) of non-hydrogen atoms in the molecule of interest in the MEDV and a topological distance for the relative distance (d) in the MEDV. For an organic molecule containing several chemical elements such as C, H, O, N, S, F, Cl, Br, I, and P, the MEDV-13 includes at best 91 descriptors. Then it is essential to employ a principal component regression (PCR) technique to derive a QSAR model relating the biological activities to the MEDV-13. The MEDV-13 is used to study the QSAR of the corticosteroid-binding globulin (CBG) binding affinity of the steroids and the activity inhibiting angiotensin-converting enzyme (ACE) of dipeptides, and resulting models have a comparable quality to the current three-dimensional (3D) methods such as CoMFA though the MEDV-13 is a descriptor based on two-dimensional topological information.

Influence of an aziridine precursor on the in vitro binding parameters of rat and ovine corticosteroid-binding globulin (CBG).

Aziridines are highly reactive alkylating compounds used in cancer treatment. Salsola tuberculatiformis Botsch., which causes prolonged gestation in sheep and contraception in rats, contains a very labile hydroxy-phenylaziridine or its precursor. A less labile analogue, 2-(4-acetoxyphenyl)-2-chloro-N-methyl-ethylammonium chloride (Compound I), was synthesized and has been shown to be contraceptive in rats and to be stabilized by corticosteroid-binding globulin (CBG). The current study compared the binding parameters of rat and ovine CBG and evaluated the effect of the aziridine precursor, Compound I, on these parameters. Kd and Bmax values of 0.646 and 578 nM for corticosterone binding to rat CBG and 0.577 and 19.8 nM for cortisol binding to sheep CBG, respectively, were measured. In competitive binding studies with rat plasma, Ki values of 3.48 nM, 0.856 nM, 22.2 nM, 722 microM, and > 1,000,000 microM for cortisol, corticosterone, progesterone, Compound I, and synephrine (Compound II), respectively, were found, while in sheep plasma the values were 0.409 nM, 1.78 nM, 5.28 nM, 594 microM, and > 1,000,000 microM, respectively. Concentrations of Compound I equivalent to an effective pharmacological dose resulted in a significant (P < 0.01) decrease in CBG bound corticosterone and a significant (P < 0.01) increase in free corticosterone in rat plasma. In sheep, a similar effect was observed with cortisol. Progesterone binding, however, did not appear to be affected significantly by Compound I in either rat or sheep plasma. Compound I was found to be a competitive inhibitor of glucocorticoid binding to CBG. These results suggest that binding of Compound I to CBG with concomitant displacement of endogenous glucocorticoids, but not progesterone, may be part of the mechanism of action of these phenylaziridine compounds.

Effect of prenatal betamethasone administration on maternal and fetal corticosteroid-binding globulin concentrations.

OBJECTIVE: This study was undertaken to examine the effects of prenatal betamethasone administration on corticosteroid-binding globulin concentrations in maternal and fetal plasma and amniotic fluid. STUDY DESIGN: Two groups of patients with preterm labor at 24 to 35 weeks' gestation who were receiving prenatal betamethasone (2 intramuscular doses of 12 mg) were studied. Maternal plasma was obtained before and at variable intervals until 1 week after betamethasone administration. Umbilical cord blood and amniotic fluid samples were collected at the time of delivery. Samples were also collected from patients at risk for preterm delivery who did not receive glucocorticoids. RESULTS: Betamethasone suppressed maternal cortisol concentration by >70% within 24 hours of injection but did not significantly alter corticosteroid-binding capacity or relative concentrations of corticosteroid-binding globulin isoforms in either maternal or umbilical cord plasma. Betamethasone reduced corticosteroid-binding capacity in amniotic fluid within 24 hours of injection, and values remained suppressed 1 week after treatment. CONCLUSION: Maternal and fetal plasma corticosteroid-binding globulin concentrations were unchanged after maternal betamethasone administration at 24 to 32 weeks' gestation but amniotic fluid corticosteroid-binding globulin concentrations decreased significantly, suggesting different sites of either corticosteroid-binding globulin production or regulation or both.

The glucocorticoid receptor is essential for maintaining basal and dexamethasone-induced repression of the murine corticosteroid-binding globulin gene.

We have investigated hepatic expression and glucocorticoid regulation of the corticosteroid-binding globulin (CBG) gene in mice lacking a functional glucocorticoid receptor (GR). GR-/- mice show impaired negative feedback in the hypothalamic-pituitary-adrenal axis, resulting in elevated circulating levels of ACTH and corticosterone. This is seen in the neonatal period and continues into adulthood where ACTH and corticosterone levels are increased up to 4-5 fold. Despite high elevation of corticosterone we find no change in mean arterial blood pressure in GR-/- mice and no change in the renal activity of the glucocorticoid-metabolising enzymes 11beta-hydroxysteroid dehydrogenase type-1 (HSD1) and type-2 (HSD2). We do find markedly increased hepatic expression of CBG with a 50% increase in plasma CBG levels. Increased expression of CBG was detected in adult GR-/- mice and also at birth with a greater than 10-fold increase in CBG hepatic mRNA in day-18.5 embryonic GR-/- mice. Adult GR-/- mice were also resistant to dexamethasone-induced repression of CBG expression in the liver. These results indicate that in mice, GR is essential for maintaining the basal level of CBG gene expression in the liver, and is also required for dexamethasone-induced repression of the CBG gene in the adult.

Chronic exposure to morphine increases corticosteroid-binding globulin.

Although it appears that corticosterone may play an important role in determining vulnerability to drugs of abuse, few studies have examined drug effects on factors that affect corticosterone efficacy. Thus, studies were carried out to assess the effects of morphine on corticosteroid-binding globulin (CBG), the major glucocorticoid binder in blood. Since CBG-bound hormone is thought to be physiologically inactive, changes in CBG levels could affect corticosterone action independently of hormone levels per se. We found that morphine caused a marked naltrexone-preventable increase (approximately 160%) in CBG in adult male rats. Elevated levels were seen by three days and were maximal at seven days after morphine pellet (75 mg) implantation. CBG levels remained elevated while morphine was detectable in blood and returned toward normal as the drug cleared from the system. A single morphine pellet was sufficient to induce a marked increase in the concentration of CBG and two or more pellets caused maximal upregulation. Baseline and stress levels of total corticosterone (bound and unbound) were normal after chronic exposure to morphine. However, due to the elevated level of CBG, the amount of free, physiologically active hormone was dramatically reduced. These results suggest that morphine may exert potent effects on corticosterone action that are not revealed by measurement of corticosterone alone. Furthermore, the increase in CBG resulting from chronic exposure to morphine might contribute to the perpetuation of drug use and to adverse effects of drug exposure by impairing normal functions of corticosterone.

The effects of estradiol-17 beta infusion into fetal sheep in late gestation.

Activation of the hypothalamic-pituitary-adrenal (HPA) axis of fetal sheep during late gestation is associated with increases in plasma concentrations of adrenocorticotropic hormone (ACTH) and cortisol, and ultimately results in parturition. However, the mechanisms contributing to the concurrent increases in ACTH and cortisol are unclear. Plasma estradiol-17 beta (E2) concentrations increase progressively in the prepartum ovine fetus, and we hypothesized that E2 may influence HPA activity by affecting either basal and/or hypoxemia-stimulated ACTH release. We examined potential mechanisms, including altered expression of pro-opiomelanocortin (POMC) in fetal pituitary corticotrophs, and changes in corticosteroid binding globulin (CBG) and/or the enzymes 11 beta hydroxy steroid dehydrogenase (11 beta HSD)-1 or 11 beta HSD-2 in liver and placenta, that could alter negative feedback control. We infused fetal sheep at 127 d of gestation with either E2 (100 micrograms/24 h) or saline for 100 h. Fetal arterial blood samples were collected at 8 h intervals during the infusion of E2 or saline (n = 4), for measurement of basal plasma ACTH and cortisol concentrations, as well as plasma corticosteroid binding capacity (CBC). Placenta and fetal liver samples were collected at 100 h for measurement of placental 11 beta HSD-1 and 11 beta HSD-2 mRNA and hepatic CBG and 11 beta HSD-1 mRNA, by Northern blotting. Fetal pituitary samples were collected for measurement of POMC mRNA by in situ hybridization. In a separate experiment, fetuses were exposed to 2 h of hypoxemia at 75 h of E2 or saline infusion (n = 4), and fetal arterial blood samples were collected during the period of hypoxemia for measurement of plasma ACTH and cortisol concentrations. E2 infusion had no effect on basal plasma concentrations of ACTH or total cortisol, or on the stimulated levels of ACTH or total cortisol achieved in response to hypoxemia. Basal fetal pituitary POMC mRNA also did not change significantly with E2 infusion. No significant increases were observed in plasma CBC during E2 administration. However, hepatic CBG and 11 beta HSD-1 mRNA were significantly elevated in the livers of E2-treated fetuses. Placental 11 beta HSD-1 mRNA; but not 11 beta HSD-2 mRNA was increased by E2 treatment. These data do not support a direct effect of exogenous E2 at the level of basal or hypoxemia-stimulated ACTH output, but suggest that elevated E2 concentrations may alter the expression of genes encoding proteins implicated in tonic regulation of fetal HPA function.

Inhibition of ovulation by an oral contraceptive containing 100 micrograms levonorgestrel in combination with 20 micrograms ethinylestradiol.

Twenty-four healthy female volunteers with normal ovulatory cycles, aged between 20 and 34 years (27.5 +/- 4.3), were included in a single-center, non-comparative study to investigate the effect on inhibition of ovulation of an oral contraceptive containing 20 micrograms ethinylestradiol in combination with 100 micrograms levonorgestrel. At baseline, during three treatment cycles and post-treatment, ultrasonography was used to examine the ovaries, to measure follicular size, and to measure the thickness of the endometrium. Serum levels of LH, FSH, estradiol, progesterone, total testosterone, free testosterone, SHBG, and CBG were also measured. Compared with treatment cycle 1, an increase in residual ovarian activity (follicle grades 4-5) was observed in cycles 2 and 3. Mean levels of LH, FSH, 17 beta-estradiol and progesterone remained suppressed during treatment. No escape ovulation was observed during the treatment phase of the study and there were no pregnancies. Ovulation was noted to return rapidly in the posttreatment cycle. Subjective and objective tolerance of the present regimen was noted to be good. Results indicate that the monophasic oral contraceptive containing 100 micrograms levonorgestrel combined with 20 micrograms ethinylestradiol effectively inhibits ovulation, providing adequate suppression of ovarian activity.

Differential effects of betamethasone and dexamethasone fetal administration of parturition in sheep.

OBJECTIVE: We tested the hypothesis that betamethasone is more potent than dexamethasone in inducing the essential mechanisms of parturition in sheep. METHODS: Twenty-one sheep were instrumented under general anesthesia with maternal and fetal arterial and venous catheters and myometrial electromyogram electrodes at 117 days' gestation (dGA). At 125 dGA at 12:00 PM, after 2 days of baseline recording, either saline (n = 7, control group), betamethasone (n = 7), or dexamethasone (n = 7) was administered into the fetal jugular vein at a rate of 10 micrograms/hour. A total dose of 0.48 mg was given over the next 48 hours. The animals underwent autopsy 3 days after the end of the infusion period (130 dGA), or earlier if labor resulted from the glucocorticoid administration. Daily maternal and fetal arterial blood samples (4 mL) for hormone measurement were taken at 10:00 AM throughout the study period. Additional arterial blood samples were taken if the animal developed labor. Maternal plasma progesterone and fetal ACTH and cortisol concentrations were measured by radioimmunoassay, and corticosteroid-binding globulin (CBG) binding capacity was determined by saturation analysis. Myometrial activity was monitored continuously throughout the experimental protocol. RESULTS: All seven betamethasone-treated animals developed labor after the glucocorticoid infusion regimen. In contrast, only two of seven dexamethasone-treated animals developed labor. Fetal treatment with betamethasone produced a greater and earlier fall in maternal plasma progesterone than fetal treatment with dexamethasone. Both betamethasone and dexamethasone treatments elevated fetal plasma CBG to similar binding capacities. Elevated fetal plasma ACTH and cortisol concentrations at the end of the infusion period in both betamethasone-and dexamethasone-treated animals were not related to the development of labor-type contractions. CONCLUSION: These data support the hypothesis that betamethasone is more potent than dexamethasone in inducing the essential mechanisms of parturition in sheep.

Regulation of corticosteroid-binding globulin synthesis by 1alpha,25-dihyroxy-vitamin D3 (calcitriol), 9-cis-retinoic acid and triiodothyronine in cultured rat fetal hepatocytes.

Evidence regarding the nature of the regulatory factors which directly act upon liver cells and extra-hepatic tissues to alter CBG synthesis is scarce. The present study used cultured rat fetal hepatocytes to investigate the involvement and possible interplay in this process of several members of the nuclear receptors superfamily: vitamin D (VDR), retinoic acids (RAR/RXR) and thyroid hormones (TR). Treatment of cells with 1alpha,25-(OH)2D3 (1,25-D) elicited a dose-dependent inhibition of basal CBG concentration in culture medium. Maximum inhibition to about 15% of control level was achieved with 0.1-1.0 nM, with an IC50 of 3.8 x 10(-12) M and with no significant change in binding affinity. Differential activation of RAR and RXR with either 9-cis-retinoic acid (9-cis-RA) or the RAR-selective synthetic retinoid TTNPB revealed that high doses of both drugs diminished CBG expression, though the former proved about 10-times more potent than the latter in this regard. Amplification by triiodothyronine (T3) of CBG synthesis failed to block the inhibitory effects of either 1,25-D or retinoids, as revealed by both binding capacity and mRNA measurements. Relative to CBG, 1,25-D similarly depressed the synthesis of alpha-fetoprotein (AFP), while on the contrary, retinoids and T3 were shown to cause opposite effects, as 9-cis-RA and TTNPB elevated and T3 decreased AFP expression. The present findings identify for the first time ligands of VDR and RAR/RXR as powerful negative regulators of both basal and T3-stimulated CBG biosynthesis in fetal hepatocytes and suggest lack of a functional interplay between TR and VR or RAR/RXR in these processes.

[The functional characteristics of the hypophyseal-adrenal system in female mice with a hereditary autoimmune pathology]. / Osobennosti funktsionirovaniia gipofizarno-nadpochechnikovoi sistemy u samok myshei s nasledstvennoi autoimmunnoi patologiei.

Functional activity of the pituitary-adrenal axis was studied in genetically autoimmune mice (NZB strain). Young and healthy females (2-3-month old) had high total plasma corticosteroids which sharply decreased by the 6-7th month when the first anti-erythrocyte autoantibodies appeared. At the same time, their ACHT plasma concentration significantly increased compensating, probably, for the low level of corticosteroids. At 6-7 month of age, the amount of corticosteroid-binding globulin was significantly increased therefore decreasing the pool of the active hormones. Low doses of dexamethasone increased the pool of free active glucocorticoids and prevented development of autoimmune processes. The data obtained suggest a possible role of endogenous glucocorticoids in the protection against autoimmune disease.

[The characteristics of the programming action of androgens on the formation of sexual dimorphism in the level of corticosteroid-binding globulin in rats]. / Osobennosti programmiruiushchego deistviia androgenov na formirovanie polovogo dimorfizma urovnia kortikosteroidsviazyvaiushchego globulina u krys.

The role of sex steroids in the programming of the level of serum corticosteroid binding globulin (CBG) of male and female rats has been studied at different stages of ontogenesis. It was shown that castration of adult males lead to the increase of the level of CBG, but not to the elimination of sex differences. Gonadectomy of males up to 28th day of postnatal life results in complete feminization of the CBG content in these animals at the age of 10-12 weeks. The castration after 35th day of life does not prevent the formation of the male phenotype of CBG content. The results of administration of testosterone-propionate (TP) to castrated males at different periods of ontogenesis suggests that the sensitivity to irreversible negative action of androgens appears after 28th day of life and disappears after the puberty. It was concluded that short period of ontogenesis from 29th to 35th days of life is critical for the realization of the irreversible masculinization of CBG level upon the influence of androgens in the physiological conditions. It was found that injections of both synthetic estrogens diethylstilbestrol or TP in the sensitive period of ontogenesis lead to the expression of male phenotype of CBG level in a similar fashion.

[The hormonal mechanisms of the programming and regulation of liver function differentiation by sex]. / Gormonal'nye mekhanizmy programmirovaniia i reguliatsii differentsirovki funktsii pecheni po polu.

Crucial role of androgens and estrogens in programming and regulation of the sex-dependent expression of a specific estrogen-binding protein, androgenous and estrogenous receptors and corticosteroid-binding globulin, was shown. Both types of the sex steroids effects were shown to be realized in the hepatocytes through respective hormonal receptors. The realization of physiological effects of the sex hormones demands the participation of STH as a permissive factor. Some theoretical and practical aspects of the sex differentiation of the liver functions, are discussed.