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Query: UMLS:C0338671 (Steroids)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An assay for plasma glucocorticoid activity has been developed using specific glucocorticoid receptors. Unlike other assays for cortisol and certain synthetic corticosteroids, this radioreceptor assay measures the glucocorticoid activity of all natural an synthetic steroids. Steroids extracted from as little as 0.05 ml of plasma are incubated with 3H-dexamethasone and cytosol receptors from cultured rat hepatome cells. From 0.5 to 50 ng of cortisol are accurately detected. Glucocorticoid activities of adult determined by the assay correlate closely with corticoid levels obtained in the CBG-isotope and fluorometric assays. Other steroids are measured in proportion to both concentration and potency as glucocorticoids. Relative activities include: cortisol 100, dexamethasone 940, prednisolone 230, prednisone 3, estradiol 1 and androstenedione 1. A similar ranking of steroids was found using receptors from a human source (fetal lung). The assay has been useful in detecting glucocorticoid activity in unidentified medications and in measuring plasma glucocorticoid levels after administration of synthetic corticosteroids. A modification of the assay is described for also estimating the level of free (unbound) glucocorticoid activity in plasma. Assays are performed before and after removal by charcoal of steroids not bound to plasma transcortin. This consideration is shown to be particularly important with prednisolone where the unbound steroid level is much less than the total. Thus, the radioreceptor assay provides a relatively simple technique for measuring the total of free plasma of glucocorticoid activity in man due to any natural or synthetic steroid or combination of steroids.
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PMID:A radioreceptor assay for evaluation of the plasma glucocorticoid activity of natural and synthetic steroids in man. 16 79

A simple, sensitive and reliable competitive protein binding radioassay using dog transcortin has been developed for the measurement of 11-deoxycorticosterone (DOC) in human plasma. A 1% plasma solution from dexamethasone treated male dogs served as the source of the binding protein. Sephadex LH-20 column chromatography was used for the separation of the steroid prior to assay. The method is sensitive enough to detect 50 pg of DOC. The intra- and interassay co-efficients of variation were 11.5% and 11.3% respectively. Water blanks and plasma blanks from adrenalectomized rats and humans gave negligible readings for DOC. Support for the identity of the steroid being assayed as DOC was obtained by subjecting a plasma pool to multiple radioassays using 4 different binding proteins including 2 anti-DOC antibodies. The values obtained in all 4 systems were in good agreement confirming the fact that DOC was the steroid being measured. Morning plasma DOC levels measured in 29 healthy subjects averaged 8.0 plus or minus 1.2 (S.E.) ng% in 14 males, and 8.7 plus or minus 0.9 (S.E.) ng% in 15 females (p greater than 0.3).
Steroids 1975 Jan
PMID:A competitive protein binding radioassay for deoxycorticosterone in human plasma. 111 Nov 69

In adult male ducks submitted to marked variations in plasma testosterone concentration, plasma transcortin (CBG) levels were shown to be closely related to the level of plasma testosterone. In connection with previous data on female ducks, the results strongly support the evidence that at least in this species, CBG is under a stimulatory control by testosterone.
Steroids 1984 Apr
PMID:Androgen control of transcortin binding capacity in adult male ducks. 652 49

Corticosterone-and progesterone-binding activity were measured by saturation analysis, with dextran-charcoal separation, in plasma obtained from male and female rats, and a normal male and female human. In plasma from normal male and female rats, progesterone was much less effective than corticosterone in displacing 3H-corticosterone from plasma protein binding sites although the parallelism of the displacement curves indicated competition for the same binding sites. In plasma from the normal male human, corticosterone and progesterone were equally effective in displacing 3H-corticosterone. However, 3H-progesterone showed no apparent binding to either rat or human plasma proteins, suggesting that dextran-charcoal effectively removed progesterone from transcortin binding sites at 4 degrees C. This observation was confirmed by multiple equilibrium dialysis. In dialysis, 3H-corticosterone and 3H-progesterone were bound equally by human plasma, but rat plasma bound 3H-corticosterone to a much greater extent than it did 3H-progesterone. These data indicate that, in contrast to human plasma, rat plasma has much greater affinity for corticosterone than for progesterone.
Steroids 1980 Sep
PMID:Comparison of plasma corticosterone- and progesterone-binding activity in rat and human. 700 80

Glucocorticoid uptake by intact AtT-20/D-1 cells was studied to determine if the extent of uptake was enhanced or retarded by binding components in serum. The results demonstrate that the uptake of corticosterone, which binds to transcortin, was reduced by addition of serum while uptake of triamcinolone acetonide, which is not bound by transcortin, was unaffected. Neither heat denatured serum nor bovine serum albumin affected corticosterone uptake, further emphasizing the specificity of the inhibition. The presence of serum also affected the apparent binding specificity, since steroids able to bind to transcortin became less effective competitors when serum was present in the incubation medium. In the absence of serum, the specificity of glucocorticoid uptake was qualitatively similar to that of the isolated cytosol receptor. These results emphasize that the selective inhibitory effect of serum transcortin on whole cell uptake of certain steroids should be considered when assaying steroid potency in intact cellular systems.
Steroids 1981 Feb
PMID:Conditions affecting AtT-20 cell glucocorticoid uptake. 722 46

Corticosteroid-binding globulin (CBG or transcortin) is a specific plasma glycoprotein, which binds steroid hormones (cortisol, corticosterone, and progesterone), and plays a role in transporting these steroids, altering their concentrations in blood, and influencing their biological actions. CBG has been previously shown to be synthesized in the liver, but recently it has been reported that immunoreactive CBG is localized in target tissues. In the present work, CBG mRNA was detected in normal human endometrial tissues by Northern blot analysis and reverse transcription-polymerase chain reaction. Its level was higher (P < 0.05) in the secretory phase than in the proliferative phase. In the secretory phase, the endometrial CBG mRNA level was negatively correlated with the serum progesterone level (P < 0.01). While there was no positive correlation between the levels of endometrial CBG mRNA and serum estradiol (E2), there was a positive correlation between the endometrial CBG mRNA level and the serum E2/progesterone ratio (P < 0.05). These findings suggest that CBG is synthesized in the uterine endometrium, predominantly in the secretory phase, and that the serum E2/progesterone ratio exerts an influence on the synthesis of intracellular CBG.
Steroids 1994 Oct
PMID:Corticosteroid-binding globulin mRNA levels in human uterine endometrium. 787 88

Genomic DNA was isolated from two related individuals who are homozygous for transcortin Leuven, a corticosteroid-binding globulin variant with decreased cortisol-binding affinity. This material was amplified using intron-specific oligonucleotide primers in a polymerase chain reaction to obtain the four exons that encode transcortin. Sequence analysis of these exons showed several mutations within the coding sequence of both individuals, but only one of these will result in an amino acid substitution. This mutation is located within exon 2 and alters the codon (CTC) normally associated with Leu-93 in the transcortin polypeptide to a codon (CAC) for histidine in the variant genes.
Steroids 1993 Jun
PMID:Decreased cortisol-binding affinity of transcortin Leuven is associated with an amino acid substitution at residue-93. 821 73

Since it has been demonstrated that corticosteroid-binding globulin (CBG) plays a role in intracellar steroidal actions in target cells, the expression of CBG mRNA as the measure of CBG expression was investigated in human endometrial cancers in order to assess the biological implications of CBG. The level of CBG mRNA was analyzed using competitive reverse transcription-polymerase chain reaction-Southern blot analysis. While the level of CBG mRNA was significantly (P < 0.01) higher in secretory phase endometrium than in early and late proliferative phase endometrium, the level of CBG mRNA tended to decrease with advanced dedifferentiation of endometrial cancers as compared to normal endometrium. These results suggest that dedifferentiation of endometrial cancers induces a reduction in intracellular CBG synthesis.
Steroids 1995 Oct
PMID:Expression of corticosteroid-binding globulin mRNA in human uterine endometrial cancers. 853 82

11 beta-hydroxyprogesterone (HOP) and 11-ketoprogesterone (KP) are reversible components of a shuttle pair whose interconversion in rat liver is catalyzed by isoform-1 of 11 beta-hydroxysteroid dehydrogenase. Kidneys also produce this interconversion. The present study was carried out to investigate the shuttle pair and its components in the rat. As in corticosterone/11-dehydrocorticosterone, oxidation is more effective at an alkaline pH, while reduction prevails at a neutral pH. Moreover, both reactions are inhibited by the detergent 3-[(3-cholamido propyl)-dimethylammonio]-1-propane-sulphonate (CHAPS). However, at variance with the 11-ketosteroids cortisone (E) and 11-dehydrocorticosterone (A) thought to be "inactive," KP has slight direct Na(+)-retaining properties, and it, as well as HOP, induces glucocorticoids (11 beta-hydroxycorticoids) to retain sodium. 11-ketoprogesterone exhibits 17 times better affinity for native type 1 mineralocorticoid receptor than HOP and a 3-fold affinity for partially purified (transcortin free) mineralocorticoid receptor. However, KP, in contrast to HOP, binds only weakly to transcortin, not at all to glucocorticoid receptor, and requires reduction at C11 for tyrosine aminotransferase (TAT) induction.
Steroids 1997 Apr
PMID:Features of the shuttle pair 11 beta-hydroxyprogesterone-11-ketoprogesterone. 909 Jul 96