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PubMed1996

Changes in plasma adrenocorticotropin, corticosterone, corticosteroid-binding globulin, and hippocampal glucocorticoid receptor occupancy/translocation in rat pups in response to stress.

Pituitary-adrenal responses to stress in the neonatal rat have been reported to be substantially reduced compared to older animals (i.e. a stress hyporesponsive period). This supposed period of endocrine quiescence is characterized by reduced stress-induced increases in both plasma ACTH and corticosterone. At the same time a number of authors have noted the decreased plasma corticosteroid-binding globulin (CBG) levels of the neonate, and there is evidence for an increased percentage of free corticosterone as well as age-related changes in the volume of distribution for corticosterone. These findings suggest that the reduced CBG levels might enhance the biological significance of existing glucocorticoid levels, beyond that assumed on the basis of plasma total corticosterone levels. We examined this question by estimating hippocampal glucocorticoid receptor occupancy and 'translocation' in Day 6, Day 15, and adult animals under basal and stressful conditions. The results showed that: 1) plasma ACTH levels were elevated in Day 6 animals in response to acute exposure to ether, maternal separation, and maternal separation + ether, however, ACTH responses were substantially lower than in Day 15 or adult animals; 2) Plasma total corticosterone levels followed a similar pattern; most noteworthy was the potent glucocorticoid response in Day 15 animals to the combination of maternal separation + ether; 3) Plasma CBG levels in Day 6 animals were extremely low (< 3% adult values); by Day 15 CBG levels were about 25% of adult levels. Interestingly, maternal separation was associated with a substantial decrease in plasma CBG levels; 4) Hippocampal glucocorticoid receptor occupancy/translocation was similar at all ages under both basal and stress conditions. The only notable exception occurred during maternal separation in Day 15 animals, where the percentage of hippocampal glucocorticoid receptor occupancy/translocation was higher than that observed at any time in either Day 6 or adult animals. This finding is likely related to the decrease in plasma CBG that occurs following separation of Day 15 pups from the dam. Thus, despite the higher corticosterone level in the adult, the increase in glucocorticoid receptor occupancy/translocation was generally comparable across all ages either under basal conditions, or following stress. These receptor data underscore the importance of developmental changes in plasma CBG levels.

Adrenalectomy↗
PubMedDate not supplied

Evidence for the synthesis and secretion of a CBG-like serpin by human cumulus oophorus and fallopian tubes.

The acrosome reaction (AR)-inducing effect of follicular cells, like that of the cumulus oophorus and granulosa cells, has been described previously. In addition to the well known steroid secreting activity of cumulus cells, the results obtained here demonstrate the secretion of a corticosteroid-binding globulin (CBG)-like protein. An AR-inducing effect was shown with the culture medium of human cumulus oophorus. This effect could be eliminated by treating the sample with monoclonal antibodies against CBG. Moreover, Western blotting after SDS-PAGE of the culture medium strongly indicates that human cumulus cells actively express and secrete a CBG-like protein. This might give an indication as to the origin of the acrosome reaction-inducing substance found in follicular fluid. Furthermore, AR-inducing activity and the elimination of this activity by antibodies against CBG was shown for oviductal fluid. With immunohistochemical techniques the CBG-like protein was localized in the epithelial lining of the fallopian tubes, giving possible evidence for the involvement of this molecule in fallopian tube function.

Fallopian Tubes↗
PubMed1995

Hormone profiles around weaning in cyclic and anoestrous sows.

Peripheral plasma patterns of LH, cortisol, corticosteroid-binding globulin (CBG) and beta-endorphin were studied around weaning in sows that resumed cyclicity and those that remained anoestrus after weaning. Average LH concentration in both groups of sows, and basal LH concentration, LH pulses/6 h and the sum of LH pulses and peaks/6 h in the cyclic sows, increased from the day before weaning to significantly higher (P < 0.05) levels on the days after weaning. Overall, average and basal LH concentrations were higher (P < 0.05) in the sows that resumed cyclicity than in those that remained anoestrus. Cortisol and beta-endorphin concentrations were high before weaning and on the day of weaning in both groups of sows. Cortisol in the cyclic sows, and beta-endorphin in both groups of sows, decreased (P < 0.05) after weaning. CBG levels were unchanged until the second day after weaning when there was an increase (P < 0.05) in both groups of sows. Before and even after weaning cortisol, CBG and beta-endorphin levels tended to be higher in the sows that remained anoestrus compared with those that resumed cyclicity. Findings in the present study show higher levels of cortisol, CBG and beta-endorphin before weaning that persisted even after weaning, and lower LH concentrations around weaning in sows that failed compared with those that resumed oestrous activity.

Animals↗
PubMedDate not supplied

Hypothalamic-pituitary adrenal function in end-stage non-alcoholic liver disease.

Patients with end-stage liver disease have significant mortality often associated with intercurrent episodes of bleeding or sepsis. Intact adrenal function is essential in such situations. In order to test the hypothesis that adrenal insufficiency might be present in severe liver disease, hypothalamic-pituitary adrenal function was evaluated in patients with end-stage liver disease awaiting transplantation. The study had a prospective, open comparative design with patients restricted to those having non-alcoholic liver disease in order to avoid the confounding direct effects of alcohol on adrenocortical function. Fifty-one consecutive patients with end-stage, non-alcoholic liver disease undergoing evaluation for liver transplantation and 40 healthy controls were studied. Patients who had used corticosteroids (n = 8) or who were unable to complete the investigations (n = 5) were excluded leaving 38 patients eligible for analysis. Adrenal function was evaluated under basal conditions by single morning measurements of plasma total and free cortisol, corticosteroid-binding globulin, dehydroepiandrosterone sulfate and by adrenal stimulation indirectly using insulin-induced (0.1 U/kg, i.v.) hypoglycaemia and/or directly by adrenocorticotrophic hormone (ACTH); 250 micrograms tetracosactrin, i.v.) stimulation. Compared with healthy controls, patients with liver disease had a 64% reduction in maximal increments of plasma cortisol to indirect adrenal stimulation via insulin-induced hypoglycaemia and a 39% reduction to direct adrenal stimulation by ACTH (all P < 0.001). There was a significant negative correlation between the severity of underlying liver disease as assessed by Child-Pugh scores and peak control responses to ACTH (r = -0.647, P < 0.0001) and insulin-induced hypoglycaemia (r = -0.597, P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2004

Plasma sex hormone-binding globulin rather than corticosteroid-binding globulin is a marker of insulin resistance in obese adult males.

AIM: Plasma levels of corticosteroid-binding globulin (CBG) and sex hormone-binding globulin (SHBG) may be regulated by insulin. The aim of this study was to test the hypothesis that these steroid-binding proteins are markers of insulin resistance and obesity in adult patients with the metabolic syndrome. METHODS: Fasting blood samples were obtained from 108 male and 88 female overweight adult patients who had varying degrees of dyslipidaemia, adiposity and insulin resistance. We measured plasma levels of SHBG and CBG and investigated their correlation with insulin resistance [homeostasis model assessment (HOMA) % sensitivity] and anthropometric markers of adiposity. RESULTS: In male patients, plasma SHBG correlated positively with HOMA (% sensitivity) and negatively with anthropometric measurements, including body mass index, waist circumference (cm) and percentage body fat. There was no correlation with CBG and any other parameter in the male patients. The female patients were treated as two groups, those not using oral contraceptives or hormone replacement therapy (n = 67) and those taking steroid medications (n = 21). Female patients using steroid medications had significantly higher SHBG levels but neither group showed any correlation between SHBG, insulin resistance and adiposity. Correlation studies of CBG with other parameters in the female subgroups did not reach statistical significance. CONCLUSIONS: We conclude that plasma SHBG is another surrogate marker for insulin resistance in obese males but not in obese females. It also appears that plasma CBG is not a useful marker of insulin resistance in patients with the metabolic syndrome.

Biomarkers↗
PubMed1987

Alcohol-induced changes in pituitary-adrenal activity during pregnancy.

This study examined the interactive effects of ethanol and nutritional status on pituitary-adrenal function of pregnant females consuming high doses of ethanol throughout gestation. Three liquid diets were formulated ranging in protein content from suboptimal to supraoptimal (18%, 25%, or 32% of total calories) in terms of pregnancy requirements, while ethanol was held constant at high levels (36% of total calories). In addition to the alcohol group (A), both pair-fed (PF) and ad libitum-fed control (C) groups were included in each diet regimen. Basal levels of corticosterone and the adrenocortical response to stress were measured in dams on days 11, 16, or 21 of gestation. Plasma levels of corticosterone-binding globulin (CBG) were also measured on gestation days 16 and 21. Maternal adrenal weights, basal corticosterone levels, the adrenocortical response to stress, and the corticoid stress increment were all significantly increased in A compared to both PF and C females. Plasma CBG levels of A females were similar to or less than those of PF and C females. Thus alcohol consumption significantly increased maternal pituitary-adrenal activity as early as day 11 of gestation and these effects on hormonal function increased as gestation progressed. This adrenocortical hyperactivity was relatively unaffected by maternal nutritional status and thus appears specific to alcohol.

Alcoholism↗
PubMed1989

Prenatal ethanol exposure alters adrenocortical development of offspring.

Interactive effects of prenatal ethanol and maternal nutritional status on reproductive outcome and maternal and offspring adrenocortical activity were examined. Ethanol was administered to pregnant females in liquid diets (36% ethanol-derived calories) which were marginal or optimal in terms of requirements for pregnancy. Both pair-fed and ad libitum fed control groups were included. Females consuming ethanol from gestation Day 1 through parturition gained less weight, were delayed in parturition, and had fewer and smaller live born young than pair-fed or control females, regardless of whether they consumed marginal or optimal diets. Withdrawing ethanol on Day 21 of gestation attenuated many of ethanol's adverse effects on reproductive outcome. However, prenatal maternal ethanol intake altered adrenocortical activity/responsiveness of the mother, the fetus, and the preweaning offspring, regardless of maternal nutritional status. Relative adrenal weights and basal corticosterone levels were increased in the dam both prenatally and at parturition. Ethanol-exposed fetuses (A) had increased relative adrenal weights but lower basal corticosterone levels than pair-fed (PF) and control (C) fetuses on gestation Day 21. At birth, plasma and adrenal corticosterone levels were increased, while absolute adrenal weights and corticosterone binding globulin (CBG) binding capacity were decreased in A neonates. At 5 days of age, A pups showed reduced plasma corticoid responses to ether at 15 min poststress and to novelty or saline injection at 90-min post stress compared to PF and C pups. CBG binding capacity was also reduced in A pups. At 10 days of age, plasma corticosterone levels were lower overall in A and PF than in C pups following exposure to a number of different acute stressors while at 18 days plasma corticoids were decreased and adrenal corticosterone was increased in A compared to PF and/or C pups. These data support and extend previous studies indicating that in utero ethanol exposure alters postnatal adrenocortical development. This effect is specific to ethanol and unaltered by maternal nutritional status.

Adrenal Cortex↗
PubMed1988

Are corticosteroid-binding globulin and sex hormone-binding globulin hormones?

Because it no longer seemed reasonable to us that the sole function of the steroid-binding proteins in plasma was to serve as a buffer reservoir for steroid hormones, we conducted experiments which sought out other possibilities. Both CBG and SHBG bind to cell membranes, and this interaction partakes of the general characteristics of peptide hormone-membrane receptor systems. Additionally, human CBG has the ability to cause an increase in the activity of membrane-bound adenylate cyclase in MCF-7 cells, and this, in turn, results in an increase in cellular cAMP content. Thus, CBG appears to be a protein hormone. As a first consideration, one might presume that because CBG's half-life is measured in days, it would be counted among the hormones which, for the most part, are tonic in their effects, e.g., thyroid hormone. However, two important considerations tend to believe this presumption: (1) CBG which is unoccupied by steroid is not hormonally active (Figure 5): (2) Depending upon the time of day, circulating CBG is approximately 0-60% occupied in normal humans. These observations result in a circumstance in which a substantial portion of circulating CBG is available for activation by bursts of cortisol secretion. It seems prudent to speculate that, because steroids are essential for CBG's activity, the hormonal role of CBG may be entwined with, or complementary to the steroids which it binds. Finally, we should comment on the impact that our model of CBG as a hormone has on the view that only unbound steroid can be hormonally active. First, it should be stated that we have not addressed this question experimentally. Although there is evidence that CBG may be required for cortisol action, we feel that an obligate role for it is not documented adequately. At this time, we believe that CBG's hormonal role is compatible with a hypothesis that encompasses the view that unbound steroid hormones can diffuse into cells in some tissues and that both free and bound steroid can enter cells in others. Obviously, the final word on these important topics, as always, awaits the proper experiments.

Binding Sites↗
PubMed2003

Transcriptional control of dopamine neuron development.

Recent studies have identified several factors that influence the development of midbrain dopamine (DA) neurons. The identity of early proliferating DA progenitor cells are specified by the secreted factors sonic hedgehog and fibroblast growth factor 8, derived from the floor plate of the ventral midline and the mid/hindbrain border, respectively. While transcription factors specifically expressed in the proliferating DA progenitor cells remain to be identified, several transcription factors important for postmitotic DA cell development have been characterized. These include Nurr1, Lmx1b, Pitx3, and En1/En2. The studies of these transcription factors have not only increased the understanding of how DA neurons are generated in vivo, but also allowed the development of new strategies using stem cells for engineering DA neurons in vitro, results that may have significance in future therapies of patients with Parkinson's disease.

Animals↗
PubMed1993

Foetal endocrine maturation.

In domestic ruminants such as the sheep, birth is effected through sequential maturation of the foetal hypothalamic-pituitary-adrenal (HPA) axis, leading to the increased output of cortisol. Factors regulating foetal pituitary adrenocorticotrophin (ACTH) secretion have been delineated, and these include corticotrophin releasing hormone (CRH), arginine vasopressin, prostaglandin (PG) E2 and endogenous opioids. The pre-partum increase in foetal plasma ACTH is associated with a rise in pro-opiomelanocortin (POMC) mRNA in the foetal pars distalis, and with an altered pattern of POMC post-translational processing. Foetal adrenal activation results from an increase in ACTH receptors and enhanced coupling through the Gs protein to adenylate cyclase, and increased expression of key steroidogenic enzymes including P450c17. Cortisol modulates the mechanism by which ACTH activates foetal adrenal function, through specific glucocorticoid receptors (GR) in the foetal adrenal cortex. Although the numbers of GR change with gestation, the relative abundance of GR mRNA does not, pointing to post-translational regulatory mechanisms. Cortisol also stimulates an increase in the concentration of its own high affinity binding protein (corticosteroid binding globulin; CBG) in the foetal circulation, apparently by increasing CBG gene expression in the foetal liver, and by altering the extent of foetal CBG glycosylation in a manner that would be expected to decrease the metabolic clearance of this glycoprotein. Clear evidence for placental CRH and ACTH production is lacking in sheep, but PGE2, produced in increasing amounts by the placenta during late pregnancy, may augment the drive to HPA maturation. Aspects of the maturational pathway of cortisol biosynthesis have been described in other species, including the horse, and some comparison is made with the more detailed information currently available from species such as the sheep.

Animals↗
PubMed1984

Representation and quantitation of the binding interaction between prednisone, prednisolone and corticosteroid binding globulin.

The interaction between prednisone and prednisolone (0-500 ng ml-1) for binding sites on corticosteroid binding globulin (CBG) in rabbit plasma has been investigated. The fraction unbound of each steroid rose markedly with increasing concentration at low concentrations (250 ng ml-1), tending to a plateau (0.29 prednisone, 0.15 prednisolone) at the higher concentrations (250-500 ng ml-1), indicating both saturation of CBG and the importance of binding to albumin in higher concentrations. A method is proposed of representing graphically the prednisone-prednisolone-protein interaction in three dimensions.

Animals↗
PubMed1997

21-Hydroxy-6,19-oxidoprogesterone: a novel synthetic steroid with specific antiglucocorticoid properties in the rat.

In the rat, the conformationally highly bent steroid 21-hydroxy-6, 19-oxidoprogesterone efficiently displaces [3H]corticosterone from thymus-glucocorticoid receptors and blocks type II receptors in kidney cytosols but competes with neither [3H]aldosterone for kidney-mineralocorticoid receptors nor [3H]progesterone for uterus-progesterone receptors. It evokes Na+ retention only at very high doses (approximately 100 microg/100 g of rat weight) and is unable to induce tyrosine aminotransferase or to increase glycogen deposits in rat liver. When coincubated with corticosterone or dexamethasone, 2.5 microM 21OH-6OP inhibits 80% of tyrosine aminotransferase induction. It may therefore be used experimentally as an antiglucocorticoid virtually lacking mineralocorticoid or glucocorticoid properties as well as affinity for mineralocorticoid or progesterone receptors.

Aldosterone↗