Characterization of the corticosteroid-binding globulin response to decidualization in the hamster.

We sought to characterize the relationship between the decidualized uterus and circulating corticosteroid-binding globulin (CBG) levels during pseudopregnancy in the hamster. Blood CBG levels (as measured by [3H] cortisol binding) averaged 11-fold greater for decidualized hamsters than for sham-operated controls on day 8 of pseudopregnancy (PSP). We used sequential blood sampling from individual hamsters to monitor changes in CBG content after decidualization. The increase in blood CBG after decidualization was rapid, as evidenced by a significant difference in CBG content between sham-operated and decidualized groups within 24 h after surgery. We varied the extent of uterine traumatization to induce differing amounts of decidual tissue. Regardless of the amount of decidual tissue, all decidualized hamsters showed a significant increase in blood CBG; however, there was a dose-dependent relationship between the amount of decidual tissue formed and the magnitude of the CBG response. We used hysterectomy (on PSP day 6, after decidualization on PSP day 4) to determine if removal of the decidualized uterus influenced the duration of the CBG response. Bilateral hysterectomy blocked further increases in blood CBG, whereas in control animals (unilateral hysterectomy) blood CBG continued to increase after surgery. Thus, once the CBG response is initiated, the decidualized uterus is necessary to maintain elevated CBG levels. The findings in this study provide further evidence for the presence of a decidua-hepatic endocrine axis that appears to be responsible for elevation of circulating CBG levels during early pregnancy in the hamster.

Rat corticosteroid binding globulin: primary structure and messenger ribonucleic acid levels in the liver under different physiological conditions.

Rat corticosteroid binding globulin (CBG) cDNAs were isolated from a lambda gt11 liver cDNA library. When rat hepatic mRNA was hybrid selected and translated in vitro, a major product reacted with antibodies against rat CBG and its Mr (approximately 43,000) was consistent with a nonglycosylated, CBG precursor polypeptide. Two overlapping cDNAs produced a 1,432 nucleotide sequence with an open reading frame comprising 396 amino acids. This includes a potential signal peptide of 22 residues followed by the amino terminus of purified rat CBG. Rat CBG therefore contains 374 amino acids (Mr = 42,196), and has six consensus sites for N-glycosylation. There is 60% identity in the primary structures of rat and human CBG over 383 residues that comprise the human sequence. Furthermore, the single cysteine in rat CBG corresponds to one of two cysteines in human CBG, and this may be significant because a cysteine is located in the human CBG steroid binding site. Northern analysis of RNA from various rat tissues revealed an approximate 1.8 kilobase CBG mRNA only in the liver. Its relative abundance in a pregnant rat was only 30% higher than in an adult female; approximately 3-fold higher than in an adult male, and 25-fold higher than in the fetuses from the same animal. Southern analysis of rat genomic DNA suggests the presence of a single gene for CBG.

[Mechanisms of sex differentiation of the level of corticosteroid-binding globulin in rats]. / Nekotorye aspekty mekhanizmov polovoi differentsirovki urovnia kortikosteroidsviazyvaiushchego globulina u krys.

The role of sex steroids was studied at different stages of ontogenesis in the regulation and programming of the level of corticosteroid binding globulin (CBG) in the blood serum of female and male rats. The blood concentration of CBG was shown to be a sex determined feature: its level in female rats was a 2.5-fold higher than that in male rats; sex differences of this function of the liver were preserved in a primary culture of hepatocytes. Androgens (A) in adult animals were shown to decrease the level of CBG, and estrogens (E) did not influence the blood level of this protein. Castration of adult males leading to an increase of the level of CBG by 1.5-fold did not eliminate sex differences. However gonadectomy of males on the first day of the life or in prepubertal period (at the age of 3-4 weeks) resulted in complete "feminization" of the CBG content in these animals at the age of 10-12 weeks. Ovariectomy in female rats in the prepubertal period did not influence the level of CBG in adult female rats. The administration of A to females or castrated males did not prevent the development of a high level of CBG at older age. Irreversible suppression of the level of CBG in adult animals could be artificially induced by the administration of A to gonadectomized female and male rats in the prepubertal period.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic analysis of extrathyroidal features of Obese strain (OS) chickens with spontaneous autoimmune thyroiditis.

The Obese strain (OS) of chickens, which is afflicted with Hashimoto-like spontaneous autoimmune thyroiditis (SAT), displays elevated T cell proliferation, interleukin (IL)2 production and IL2 receptor expression upon mitogen stimulation, and defects in the neuroendocrine control of the immune system including elevated corticosteroid-binding globulin (CBG) and a deficient increase of serum corticosterone (CN) upon cytokine injection. Recently this strain has further been shown to harbor retrovirus-related sequences (endogenous virus no. 22, ev22) absent in healthy control strains. To determine the number of genes responsible for SAT-associated immunodysregulation and to unravel possible ev22 associations, we analyzed the above immune and endocrine parameters in F1 hybrids and backcrosses of the autoimmune OS B15B15 with healthy inbred CB B12B12 chickens. OS-like T cell hyperproliferation and IL2 hypersecretion in response to both concanavalin A and phytohemagglutinin were transmitted as autosomal dominant traits and co-segregated in backcross animals. In vivo hyporesponse of the OS to the corticosterone-inducing effect of cytokine preparations was inherited dominantly and the elevated CBG serum levels recessively. None of these traits appeared to be major histocompatibility complex (MHC) linked. However, while T cell abnormalities and elevated CBG serum levels were not associated with the autosomal ev22 locus, in vivo hyporesponsiveness to glucocortocoid-inducing cytokines co-segregated with this OS-specific provirus. These results add to the concept of SAT as a polyetiological and plurigenetic disease and do not support our previous hypothesis that T cell hyperreactivity and immunoendocrine dysfunction might be functionally related.

Plasma cortisol and corticosteroid-binding globulin in essential hypertension.

Plasma concentration of cortisol, total CBG-binding capacity, and blood pressure were measured in control subjects (n = 171), patients with essential hypertension (EH; n = 210) and their first-degree normotensive (NR; n = 84) or hypertensive (HR; n = 66) relatives. Mean (+/- SD) plasma cortisol was significantly (p less than 0.001) decreased in EH (10.1 +/- 4.3 g/dl) patients and HR (11.7 +/- 4.1). Plasma cortisol in NR did not differ from control values (14.3 +/- 4.5) but the distribution of individual values covered the entire control-EH (14.6 +/- 5.5) range. Mean (+/- SD) CBG-binding capacity was significantly (p less than 0.001) lower in EH (14.4 +/- 3.0), NR (17.5 +/- 2), HR (17.6 +/- 2.2) as compared to controls (20.9 +/- 2.1), indicating that the decline in EH and in most relatives was mainly in plasma CBG-bound cortisol. The plasma CBG-binding capacity for cortisol was significantly negatively correlated with mean arterial pressure (MAP) in both controls (p less than 0.001) and NR (p less than 0.01) but not in either HR (r = 0.02) or never-treated EH patients. Total afternoon plasma aldosterone was higher (p less than 0.01 vs. controls) in 93 untreated EH patients (11.2 +/- 4.8 ng/dl) than in either 161 first-degree relatives (8.1 +/- 3.4 ng/dl) or 117 controls (7.6 +/- 3.5 ng/dl). The respective aldosterone-binding globulin (ABG) binding capacities for aldosterone were 21.2 +/- 6.7, 20.1 +/- 9.3 and 9.8 +/- 4.0%. In all these subjects taken together, there was a positive correlation between MAP and ABG-binding capacity (r = 51; p less than 0.001). The association of reduced plasma cortisol and decreased CBG binding capacity in EH may be closely related to altered steroid metabolism, which may be partly explained by an abnormality resembling a relative deficiency in adrenal 17 alpha- and 11 beta-hydroxylation. In some EH patients, hypertension may be the result of the ineffectiveness of plasma cortisol in preventing slightly elevated endogenous ACTH levels leading to an increase in ACTH-sensitive steroids.

Progestagen-dependent effect on some plasma proteins during oral contraception.

Seventeen healthy women received a combination of 0.030 mg of ethinyl estradiol and 0.150 mg of levonorgestrel or a combination of 0.030 mg of ethinyl estradiol and 0.150 mg of desogestrel for 2 years as oral contraception. Serum levels of sex hormone binding globulin, transcortin, ceruloplasmin, and pregnancy-associated protein were measured before contraception, during 3, 6, 12, 18, and 24 months of treatment, and 2 months after stopping the pill. Oral contraception with both preparations induced a similar, significant rise in both ceruloplasmin and pregnancy-associated protein. Sex hormone binding globulin levels rose significantly with the ethinyl estradiol-desogestrel, but not with the ethinyl estradiol-levonorgestrel combination. Transcortin increased with both preparations, more with the ethinyl estradiol-desogestrel combination.

A homologous radioimmunoassay for guinea pig corticosteroid-binding globulin.

A rapid, specific, and sensitive (requiring only 20 fmole of antigen equivalent to 0.007 microliter of serum) radioimmunoassay (RIA) was developed for the measurement of guinea pig corticosteroid-binding globulin (CBG). CBG was purified to homogeneity from guinea pig serum by affinity chromatography and used for immunization, as the standard and as the radiolabeled trace in the RIA. The antiserum to CBG was raised in rabbits. It was judged specific by immunoelectrophoresis and by comparison of RIA values with steroid-binding assay profiles obtained on serum separated on the basis of size and ion-exchange properties. The results of the radioimmunoassays agree with those of a steroid-binding assay run on identical samples. The sensitivity of the assay allows detection of CBG in serial serum samples, other biologic fluids such as milk, and cell culture supernatants.

Association of decreased plasma cortisol and corticosteroid-binding globulin binding capacity in patients with essential hypertension and their first degree relatives.

Both plasma cortisol and total corticosteroid-binding globulin (CBG) binding capacity were lower in 210 patients with uncomplicated essential hypertension (EH) and their 66 hypertensive first degree relatives, compared with 171 controls. However, both variables were similar in 84 normotensive relatives to those found in control subjects showing extensive variation over the entire control-EH range. The association of reduced plasma cortisol and CBG binding capacity in EH may be closely related to altered steroid metabolism which may be partly explained by an abnormality mimicking a relative deficiency in adrenal 17 alpha- and 11 beta-hydroxylation. One manifestation of this disorder in EH is an increase in the secretion rate and plasma levels of dehydroepiandrosterone sulphate (DHEA-S) which is bound with high-affinity to a low-capacity specific plasma globulin and accounts for most of the digitalis-like activity of human plasma.

Receptor-mediated pharmacodynamics of prednisolone in the rat.

A pharmacokinetic/pharmacodynamic model describing receptor-mediated effects of prednisolone is presented. The basis of the model is the generally accepted mechanism of action of steroid hormones in which corticosteroids bind to cytosolic receptors forming steroid-receptor complexes, which are activated and translocated into the nucleus. There the complexes associate with specific DNA sequences and modulate the rate of transcription of DNA into specific RNAs that code for the synthesis of proteins that elicit biological responses. Prednisolone, 5 or 50 mg/kg, was administered intravenously to adrenalectomized rats. Total plasma, free plasma, CBG-free plasma, and liver prednisolone concentrations were measured simultaneously with free hepatic cytosolic glucocorticoid receptor concentrations and tyrosine aminotransferase (TAT) activity of the liver as a function of time. The association/dissociation kinetics of prednisolone binding to the glucocorticoid receptor were measured separately in vitro at 37 degrees C. Total plasma, free plasma, and CBG-free plasma prednisolone concentrations could be used equally well in the model to account for the time course of receptor concentrations and TAT activity. However, use of liver steroid concentrations resulted in an overestimation of receptor depletion. Steroid concentrations in plasma increased 20 to 30-fold with a tenfold increase in dose, but receptor occupancy and TAT activity over time increased about threefold. While prednisolone pharmacokinetics were dose-dependent, parameters describing receptor kinetics and TAT activity were constant at each prednisolone dose. The major determinants of receptor-mediated glucocorticoid activity are confirmed to be the availability of the receptor, drug-receptor dissociation rate, and corticosteroid persistence in the biophase.

Elevation of corticosteroid-binding globulin in obese strain (OS) chickens: possible implications for the disturbed immunoregulation and the development of spontaneous autoimmune thyroiditis.

Basal plasma levels of corticosterone and corticosteroid-binding globulin (CBG) have been investigated in Obese strain (OS) chickens afflicted with spontaneous autoimmune thyroiditis (SAT). Corticosterone was determined radioimmunologically, and CBG by using a highly sensitive radioligand saturation assay. OS chickens displayed total corticosterone levels not different from healthy normal White Leghorn (NWL) chickens. CBG, however, was found to be twice as high in OS chickens as compared with their healthy counterparts, irrespective of sex or age. This quantitative difference in the CBG level is not compensated for by either altered affinity or specificity of the molecule. Furthermore, no differences were found in the response of OS and NWL lymphocytes to the suppressive effect of glucocorticoids in vitro. We therefore assume that OS animals are deficient in free, hormonally active corticosterone. An additional indication for such a diminished glucocorticoid tonus was that in vivo treatment of OS chickens with glucocorticoid hormones, thus increasing the free and active hormone fraction, normalizes the T cell hyperreactivity and significantly reduces thyroid infiltration. Possible pathophysiological implications of a diminished glucocorticoid tonus for spontaneous autoimmunity, as well as possible explanations for the beneficial effects of glucocorticoid treatment on the development of SAT, are discussed.

Transcortin and vitamin D-binding protein levels in mouse serum.

The influence of age, sex and strain on the serum concentration of transcortin (corticosteroid-binding globulin) and vitamin D-binding protein (DBP) in mice was investigated. The effect of age was studied in two strains, C57BL/6JPfd and BALB/cmHeAPfd. The concentration of transcortin and DBP increased with age. In young animals the concentration of each protein showed a significant strain difference, which disappeared in older mice for DBP, but not for transcortin. In 7-day-old animals, no sex difference was observed for either protein, but in older animals a clear sex difference was found for transcortin. Adult males tended to have somewhat higher levels of DBP than adult females, but this difference was significant only on day 70. The variation in transcortin and DBP levels was further investigated in a large number of mouse strains. The DBP concentration did not markedly vary among strains (5.98-9.65 mumol/l in males and 5.08-8.85 mumol/l in females). Transcortin, however, showed marked strain variations, ranging from 0.72 to 2.06 mumol/l in males and from 1.02 to 4.55 mumol/l in females and there was a significant correlation (r = 0.66, n = 26, P less than 0.001) between the mean transcortin levels in males and females of different strains. Interstrain variation was much higher than intrastrain variation or variation among related strains, suggesting that the transcortin concentration is largely controlled by genetically determined factors. There was a significant correlation (r = 0.82, n = 9, P less than 0.01) between the mean corticosterone and transcortin concentrations (measured at 21.00 h).(ABSTRACT TRUNCATED AT 250 WORDS)

Serum steroid binding proteins and the bioavailability of estradiol in relation to breast diseases.

Serum concentrations of sex hormone binding globulin (SHBG), corticosteroid binding globulin (CBG), and albumin were found to be normal in women with breast cancer (Ca), with benign breast disease (BBD), or with a family history of breast cancer (FHCa). Comparisons between serum steroid binding capacities and immunoassayable SHBG and CBG concentrations did not reveal abnormal forms of either protein. The serum distribution of estradiol (E2) was also determined, and women with Ca were found to have a significantly (P less than .025) higher mean percentage of non-protein-bound E2 than matched controls, but the difference was very small. In general, women with Ca also had proportionately more (P less than .05) albumin-bound E2 and less (P less than .05) SHBG-bound E2 in their sera than the controls, but the serum distributions of E2 in the BBD and FHCa subjects were the same as in controls. The dissociation rates of 5 alpha-dihydrotestosterone and E2 from SHBG in serum appear to increase with time in frozen serum samples, and this factor may effect measurements of the distribution of these steroids in serum.

Endocrine effects of high-dose ketoconazole therapy in advanced prostatic cancer.

The endocrine effects of ketoconazole (400 mg orally every 8 h) were studied in 9 previously untreated patients with advanced prostatic cancer. Five of these patients were followed for 12 months. A rapid fall in the serum concentration of testosterone was noted in all patients studied. Minimal values were observed on day 4 of treatment but thereafter serum testosterone increased slowly. The effect of the drug on unbound testosterone was relatively more important, since sex hormone binding globulin increased markedly during treatment. An increase in progesterone and LH was observed in all patients. This suggests that ketoconazole limits the conversion of C21-precursors into androgens. This block is compensated in part by activation of the hypothalamo-hypophyseal feedback system. Urinary 17-ketosteroids were decreased but 17-hydroxysteroids were unaffected by the treatment. In 5 patients followed monthly over a period of 12 months the mean testosterone concentration ranged from 69 ng/100 ml in one patient to 428 ng/100 ml in another. An excellent inverse correlation could be demonstrated between the mean serum concentration of testosterone and the mean concentration of ketoconazole. The change of serum dehydroepiandrosterone sulphate also correlated inversely with the mean ketoconazole level. Increased concentrations of oestradiol were noted in 2 patients with slight gynaecomastia. It is concluded that long-term suppression of androgen production can be realized by high-dose ketoconazole treatment and that the degree of suppression is proportional to the serum levels of the drug.

Comparison of hepatic impact of oral and vaginal administration of ethinyl estradiol.

The pronounced hepatic impact of oral ethinyl estradiol has been attributed by some to its so-called first-pass effect through the liver as only some 40% of ingested ethinyl estradiol reaches the systemic circulation. Others believe that ethinyl estradiol exerts its hepatic effects because of its chemical composition, specifically its 17 alpha-ethinyl group. In an attempt to resolve this controversy, a study was undertaken to determine whether vaginal administration of ethinyl estradiol can selectively reduce the hepatic effects of oral ethinyl estradiol. To compare the effects of oral and vaginal ethinyl estradiol, a group of postmenopausal subjects received either 5 micrograms of oral and 20 micrograms of vaginal ethinyl estradiol or 10 micrograms of oral and 50 micrograms of vaginal ethinyl estradiol in either sequence, respectively. Oral ethinyl estradiol was four to five times more potent than vaginal ethinyl estradiol. The potency ratios of the oral-vaginal ethinyl estradiol doses required to suppress follicle-stimulating hormone and luteinizing hormone were 4.4 and 3.2 and those to raise sex hormone-binding globulin binding capacity, corticosteroid-binding globulin binding capacity, and high-density lipoprotein cholesterol as well as lower low-density lipoprotein cholesterol were 3.5, 5.0, 4.2, and 4.2, respectively. These essentially equal oral-vaginal route potency ratios for both central nervous system and hepatic effects indicate that vaginal administration of ethinyl estradiol does not selectively reduce its hepatic impact in relation to its central nervous system effects. The pronounced hepatic effects of ethinyl estradiol are therefore attributed to its chemical composition.

PIP: This study assessed the bioavailability of vaginally administered ethinyl estradiol (EE) and determined the effects of 2 different doses of oral and vaginal EE of comparable bioavialability on serum follicle stimulating hormone (FSH) and luteinizing hormone (LH) concentrations as well as on corticosteroid-binding globulin binding capacity (CBG-BC), sex hormone-binding globulin capacity (SHBG-BC), high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol, and triglycerides. 5 healthly, regularly menstruating volunteers aged 26-31 years who used nonhormonal means of contraception participated in the initial phase in which bioavailability was assessed of EE in intravaginal suppositories containing 120 mcg of EE. 9 healthy postmenopausal women aged 48-67 years were randomly assigned to receive larger or smaller doses of oral and vaginal EE, each given over 25 consecutive days with a 6-week estrogen-free interval between. As a results of randomization, 2 subjects were given 10 mcg of EE orally followed by 50 mcg vaginally, 1 received 50 mcg vaginally followed by 10 mcg orally, 2 received 5 mcg orally followed by 20 mcg vaginally, and 4 received 20 mcg vaginally followed by 5 mcg orally. Oral EE was found to be 4 to 5 times more potent than vaginal EE. The potency ratios of the oral-vaginal EE doses required to suppress FSH and LH were 4.4 and 3. and those to raise SHBG-BG, and HDL cholesterol as well as to lower LDL cholesterol were 3.5, 5.0, 4.2, and 4.2, respectively. The essentially equal oral-vaginal route potency ratios for hepatic effects and central nervous system effects indicate that vaginal administration of EE is not associated with a lower hepatocellular effect of EE. It is therefore concluded that the pronounced hepatic effects or oral EE are attributable to its chemical composition, specifically its 17 alpha-ethinyl group, rather than to the 1st-pass effect through the liver.

[Comparative study of human transcortin isolated from normal donor blood and retroplacental blood]. / Sravnitel'noe issledovanie transkortina cheloveka, vydelennogo iz normal'noi krovi donorov i retroplatsentarnoi krovi.

It was demonstrated that the physico-chemical properties of human transcortin, i.e., electrophoretic, hydrodynamic and immunochemical characteristics, amino acid composition, steroid binding parameters, do not depend on the source of the glycoprotein (male or female blood, retroplacental blood). Conversely, the retroplacental blood serum was shown to contain a transcortin form whose carbohydrate component is structurally different from that of the normal donor blood transcortin. It was found that this form interacts with the sites of specific binding of transcortin in liver cell plasma membranes in a weaker degree than the donor blood transcortin.

[Transcortin concentrations in the plasma of normal persons and patients with kidney and liver diseases]. / Transcortinkonzentrationen im Plasma von Normalpersonen und Patienten mit Nieren- oder Lebererkrankungen.

The purpose of the study was to assess the influence of chronic kidney and liver diseases on the transcortin concentrations in plasma. The mean (+/- SD) plasma concentration of transcortin was 45.0 +/- 6.7 mg/l in women not taking oral contraceptive steroids and 41.2 +/- 6.7 mg/l in healthy male volunteers. Patients with the nephrotic syndrome had low transcortin concentrations (females: 20.9 +/- 8.5 mg/l; males: 26.0 +/- 6.0 mg/l). Abnormally low concentrations were measured in females treated for endstage renal disease with chronic ambulant peritoneal dialysis (CAPD) (30.8 +/- 7.5 mg/l). Patients on hemodialysis or with a functioning renal allograft had normal transcortin concentrations in plasma. Females suffering from a primary biliary cirrhosis had normal transcortin concentrations and male patients with an alcoholic cirrhosis had abnormally low mean transcortin concentrations in plasma (32.6 +/- 7.4 mg/l). The transcortin concentrations in patients with a Gilbert syndrome were normal. Among patients with a kidney or liver disease, the large variability of the transcortin concentration in plasma indicates that the knowledge of the transcortin concentration or the unbound steroid concentration in plasma is mandatory for the interpretation of total glucocorticoid concentrations in plasma.

Adaptation of the mineralocorticoid target tissues to the high circulating cortisol and progesterone plasma levels in the squirrel monkey.

Many New World primate species have elevated circulating free plasma cortisol concentrations, target tissue resistance to cortisol, and no evidence of sodium retention. A representative New World primate, the squirrel monkey (Saimiri sciureus), has plasma cortisol concentrations above those necessary to cause complete suppression of the renin-angiotensin-aldosterone axis in an Old World primate, the cynomolgus monkey (Macaca fascicularis). Despite this, the arterial blood pressure as well as the plasma sodium, potassium, and bicarbonate levels of the squirrel monkey are similar to those of the cynomolgus monkey, and its plasma aldosterone concentrations are approximately 2-fold higher. These findings suggest that cortisol has minimal sodium-retaining effects in this species. Renal cytosol aldosterone receptor concentrations are about 2- to 3-fold lower in the squirrel monkey than in the cynomolgus, whereas the receptor affinities for [3H]aldosterone are similar in the two monkeys. Higher concentrations of cortisol are needed to displace [3H]aldosterone from the mineralocorticoid receptor in the squirrel monkey than from the renal receptor in the cynomolgus [apparent equilibrium dissociation constant (Ki) = 7.8 X 10(-7) vs. 2.9 X 10(-8) M, respectively]. In addition, in contrast to man and presumably other Old World primates, plasma aldosterone concentrations in the female squirrel monkey do not increase during the reproductive cycle or pregnancy when progesterone concentrations are 10- to 20-fold higher than those of the male or the reproductively quiescent female. This suggests that progesterone is a poor aldosterone antagonist in this species. We conclude that a low concentration of mineralocorticoid receptors in New World Primates is compensated for by higher aldosterone levels, with a concomitant increase in receptor occupancy. The salt-retaining potency of cortisol is low, presumably because of a decrease in the affinity of the aldosterone receptor for glucocorticoids in New World primates.