Steroids, receptors, and response elements: the limits of signal specificity.
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Animals↗
Biomedical subjects
J W Funder
Publications and source records attributed to J W Funder.
Plasma beta-endorphin and adrenocorticotrophin in young horses in training.
A controlled period of submaximal exercise on a treadmill was used as a standardised stress test in 6 young horses to monitor the effects of training. Circulating plasma concentrations of immunoreactive beta-endorphin (IR beta-EP) were measured before, during and after the exercise period. The stress test was conducted on 3 occasions during an intensive training program lasting 14 weeks. In week 3 a marked increase in plasma IR beta-EP (P = 0.003) was demonstrated as a result of training, but by the last exercise test performed in week 9 no significant increase in plasma IR beta-EP concentrations could be detected. During the training period the basal concentrations of plasma IR beta-EP significantly decreased (P = 0.0059). Plasma adrenocorticotrophin (ACTH) did not increase during exercise, although there was a trend of decreasing basal plasma ACTH by the end of the training period. It was concluded that a standardised work test acted as a mild stress to unfit horses, but as the horses' fitness increased the hormonal response to exercise diminished. Basal plasma beta-EP concentrations were decreased with increasing fitness.
Adrenocorticotropic Hormone↗
Effect of AVP on susceptibility of ovine pituitary cells to a cytotoxic analogue of CRF.
Although exposure to arginine vasopressin (AVP) has been reported to induce anterior pituitary corticotrophs to bind and become responsive to corticotropin-releasing factor (CRF), the identity of these inducible CRF target cells is unknown. Such cells may themselves be the AVP-responsive corticotrophs or other cells that become CRF targets secondary to a paracrine signal from AVP target cells. The present study used a cytotoxin (Cx), specific for CRF target cells, that eliminates responses of treated cells to a subsequent challenge with CRF but leaves responses to AVP intact. We hypothesized that, if AVP target corticotrophs themselves become CRF targets, then the addition of AVP during treatment with Cx should render these cells susceptible to the cytotoxin and should eliminate the response to subsequent AVP as well. Ovine pituitary cells were chosen for the study because they respond more robustly than rat cells to AVP. Pretreatment of ovine pituitary cells with Cx (400 pM) or Cx plus AVP (10 nM) eliminated the adrenocorticotropic hormone (ACTH) secretory response to CRF (10 nM), as assessed 3 days later. Cx alone also reduced the secretory response to AVP from 23.9 +/- 3.4 to 11.5 +/- 1.9 ng ACTH/3 h (P less than 0.05). However, pretreatment with AVP (10 nM) plus Cx caused no further reduction in the secretory response to AVP (10.1 +/- 2.6 ng ACTH/3 h). These data suggest that, if AVP induces erstwhile non-CRF target cells to become CRF targets, then these induced cells are not themselves initially AVP target corticotrophs.
Adrenocorticotropic Hormone↗
Evidence that the central noradrenergic and adrenergic pathways activate the hypothalamic-pituitary-adrenal axis in the sheep.
These studies were undertaken to test the hypothesis that stimulation of the central noradrenergic and adrenergic pathways activates the hypothalamic-pituitary-adrenal axis in vivo in the conscious sheep. Blood samples were taken at 10-min intervals over 4 h to establish the baseline state, and then each animal received an intracerebroventricular (icv) injection of NaCl (control animals) or catecholamine [norepinephrine (NE) or epinephrine (EPI)]. A more frequent rate of venous sampling was used for the 30-min period after the icv injection, after which time the 10-min rate of blood sampling was continued for another 3.5 h. NaCl (n = 4) caused no change in pituitary-adrenal secretion. In contrast, 10 micrograms NE (n = 4) caused acute 1.9- and 3.2-fold increases in mean plasma ACTH and cortisol levels over the 1 h period post injection, and 1.6- and 2.3-fold increments in their concentrations over the 4 h postinjection period. Although 10 micrograms EPI (n = 4) did not elevate mean plasma ACTH, it produced significant 1.7- and 1.5-fold increases in plasma cortisol during the 1- and 4-h periods post injection. However, when 100 micrograms EPI was injected (n = 4), acute 9.5- and 5.5-fold increases in plasma ACTH and cortisol were seen over the 1 h period post injection, and 6.1- and 4.2-fold increments in their plasma concentration were noted during the entire post-injection period. To determine the predominant site of action of the catecholamines, we also examined the ability of NE and EPI to release ACTH from cultured ovine anterior pituitary cells. NE and EPI (10(-9)-10(-6) M) stimulated the release of ACTH in a dose-dependent manner, but with maximal increments only 1.5-fold greater than the basal secretion. NE and EPI also increased the maximal ACTH response to CRF, but did not alter the maximal ACTH release induced by arginine vasopressin.(ABSTRACT TRUNCATED AT 400 WORDS)
Adrenal Glands↗
Epithelial and adipose cells isolated from mammary glands of pregnant and lactating rats differ in 11 beta-hydroxysteroid dehydrogenase activity.
Both adipose and epithelial cells isolated from the mammary glands of pregnant and lactating rats show 11 beta-hydroxysteroid dehydrogenase (11-HSD) activity, as measured by conversion of corticosterone to 11-dehydrocorticosterone. Activity in adipose cells from pregnant rats is 3-fold higher than in lactating rats. Epithelial cells from pregnant rats show one-twentieth of the activity of adipose cells, and activity is lower still in epithelial cells from lactating rats. Explants incubated for 48 h extensively metabolized corticosterone to 11-dehydrocorticosterone, and to a much lesser extent to a second unknown metabolite which is found in tissue extracts but not conditioned medium. Mammary gland 11-HSD may thus constitute one of the physiological mechanisms preventing premature milk production in response to glucocorticoids.
11-beta-Hydroxysteroid Dehydrogenases↗
Serum levels of 5-androstene-3 beta,17 beta-diol sulphate, 5 alpha-androstane-3 alpha, 17beta-diol sulphate and glucuronide, in late onset 21-hydroxylase deficiency.
Serum sulphates of 5-androstene-3 beta,17 beta-diol (5-ADIOL-S), 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-DIOL-S) and dehydroepiandrosterone (DHEA-S), as well as 5 alpha-androstane-3 alpha,17 beta-diol glucuronide (3 alpha-DIOL-G) and unconjugated androstenedione (AD) and testosterone (T), sex hormone binding globulin (SHBG), free androgen index (FAI) and 17 alpha-hydroxyprogester-one (17OHP) were measured by specific radioimmunoassays (RIA) in 14 women with late-onset 21-hydroxylase deficiency (LOCAH), and in normal women (n = 73). The diagnosis of LOCAH was made on the finding of a (17OHP) response level greater than 30 nmol/l following ACTH stimulation, and/or an elevation of urinary metabolites of 17OHP. Mean values for serum concentrations of all steroids measured and the free androgen index (100 X T nmol/l divided by SHBG nmol/l) were significantly elevated, and SHBG levels depressed in patients with LOCAH. These studies show that in LOCAH, in addition to the unconjugated steroids AD and T, the sulphoconjugated steroids DHEA-S, 5-ADIOL-S and 3 alpha-DIOL-S are increased, as is the glucuronide conjugate 3 alpha-DIOL-G and the index of bioavailable testosterone (FAI), and that mean SHBG levels are depressed. These data suggest that as well as AD, 5-ADIOL-S and DHEA-S may act as pro-hormones for more potent steroids (T and 5 alpha-dihydrotestosterone) in peripheral tissues, while 3 alpha-DIOL-S and 3 alpha-DIOL-G may both reflect peripheral androgen metabolism in patients with LOCAH.
17-alpha-Hydroxyprogesterone↗
The biosynthesis and secretion of adrenocorticotropin by the ovine anterior pituitary is predominantly regulated by arginine vasopressin (AVP). Evidence that protein kinase C mediates the action of AVP.
This study was undertaken to define the roles of corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) in the regulation of adrenocorticotropin (ACTH) release and biosynthesis in cultured ovine anterior pituitary cells and to define the intracellular mechanisms responsible for their action. At 4 h, CRF and AVP increased both ACTH release and total ACTH content, with AVP clearly the more potent agonist (maximal ACTH release: AVP, 22.8-fold; CRF, 7.6-fold; maximal increment in total ACTH content: AVP, 1.9-fold; CRF, 1.1-fold; EC50 for ACTH release: AVP, 2.3 +/- 0.5 nM; CRF, 9.2 +/- 5.0 nM). The increase in total ACTH content was interpreted to reflect an augmentation of ACTH biosynthesis since it was abolished by 10 microM cycloheximide. Exposure of the anterior pituitary cells to increasing concentrations of forskolin or 8-bromo-cAMP elicited increases in ACTH release and total ACTH content that were similar to those caused by CRF. A 30-min incubation with phorbol 12-myristate 13-acetate (PMA) caused a dose-related translocation of protein kinase C from the cytosol to the cell membrane; after 4 h, the increases in ACTH release and total ACTH content in response to increasing concentrations of PMA were similar to those caused by AVP. Chronic (24 h) exposure to 150 nM PMA caused an almost total depletion of both cytosolic and membrane-bound protein kinase C activities. When protein kinase C-depleted cells were subsequently exposed to AVP, the increases in ACTH release and total ACTH content were markedly attenuated, but the responses to CRF were preserved. Finally, the combination of CRF and AVP, CRF and PMA, or AVP and 8-bromo-cAMP increased ACTH release and total ACTH content in a synergistic manner. We conclude that: 1) in ovine anterior pituitary cells, AVP is the predominant regulator of ACTH secretion and biosynthesis; 2) the action of AVP is predominantly mediated by activation of protein kinase C, whereas the action of CRF is likely to be mediated by activation of the cAMP-dependent protein kinase (protein kinase A); and 3) the ability of CRF and AVP to increase total ACTH content and secretion in a synergistic manner provides a demonstration in normal pituitary cells that protein kinases C and A may interact in a unidirectional manner to regulate ACTH biosynthesis in addition to ACTH release. This interaction may take place within, or between, individual corticotropes.
Adrenocorticotropic Hormone↗
Physiology, pharmacology, toxicology and strength of materials.
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Adrenal Cortex↗
At the cutting edge. Paracrine, cryptocrine, acrocrine.
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Cell Communication↗
Altered thyroidal status and the in vivo synthesis of atrial natriuretic peptide in the rat heart.
The effect of altered thyroidal status on levels of immunoreactive (ir)- atrial natriuretic peptide (ANP) in serum and the four cardiac chambers, and of tissue ANP mRNA, was determined in groups of rats given vehicle, thyroxine (T4), propylthiouracil (PTU) or T4 plus PTU for 3 weeks. Serum levels of ir-ANP were approximately 3-fold higher in T4-treated animals compared with control; levels in PTU or PTU/T4 groups were not different from control. Right ventricular ANP mRNA was below detection; in other chamber, levels rose with T4, alone or plus PTU, and fell after PTU compared with control. Atrial ir-ANP levels were unchanged by T4, but increased (left atrium, LA) or decreased (right atrium, RA) after PTU alone. After PTU/T4, some indices (e.g. tissue weight) remained at control levels, others (e.g. ANP mRNA levels) were equivalent to levels in the T4-alone group, and others (e.g. LA ir-ANP) were equivalent to those seen with PTU alone. We conclude that the role of thyroid hormones on ANP synthesis may be similar between chambers but their effects on release appear to differ widely. The extent to which this represents secondary rather than direct effects, or possible T3-versus T4-specific events, awaits elucidation.
Animals↗
Induction of ventricular morphogenesis and atrial natriuretic factor synthesis by thyroid hormone.
Thyroid hormones have been shown to increase atrial natriuretic peptide (ANP) synthesis in atria both in vitro and in vivo. In this study the effects of triiodothyronine (T3) administration on primary cultures of 6-day-old atrial and ventricular myocytes were studied. Levels of immunoreactive (ir-) ANP were determined by radioimmunoassay over 9 days of culture in cells cultured in the presence and absence of 10(-8) M T3. The proportion of immunostained nuclei was also determined and changes in cell characteristics noted over this time. Over 9 days T3 had no effect on the proportion of atrial cells immunostained for ANP, while cell and medium content of ir-ANP in treated wells doubled that of the untreated. In treated ventricular myocytes, cell and medium ir-ANP similarly increased; in addition, the proportion of immunostained cells increased by 1-2 orders of magnitude. The formation of dendritic processes was enhanced in these cultures, reflected in increased rates of spontaneous contractility. Thus it would appear that the 6-day-old myocardium exhibits profound differences in response to T3 administration, in that ventricular cells dedifferentiate and undergo morphological changes which are not seen in atriocytes.
Animals↗
Tissue-specific developmental expression of the kallikrein gene family in the rat.
Using a series of gene-specific oligonucleotide probes, we have explored the developmental pattern of expression of six members of the rat kallikrein gene family (PS, S1, S2, S3, K1, and P1) in the submandibular gland (SMG) and kidney of both sexes, the prostate and testis of the male, and the anterior pituitary gland (AP) of the female rat. PS (true kallikrein) mRNA was detected in early neonatal life in the SMG and kidney of both sexes. K1, a second kallikrein gene family member expressed in the adult kidney, had a developmental pattern similar to PS in the kidney. In contrast, tonin (S2), S3, K1, and P1, all of which are expressed in the adult SMG, did not reach detectable SMG mRNA levels until puberty in either the male or female rat. Both S3 and P1, which are expressed in the adult prostate, and the novel P1-like mRNA previously detected in the adult rat testis, first appeared in early puberty. In the female AP, PS mRNA levels were not detected until early puberty and thus exhibited a developmental profile different from that of prolactin. The demonstration that S1, S2, S3, P1, and K1 are not expressed in the SMG or prostate until puberty is consistent with the expression of these genes in these tissues being androgen-regulated; the first appearance of PS mRNA in the female AP in early puberty similarly reflects the estrogen dependence of PS gene expression in this tissue. The presence of PS mRNA levels in the SMG and kidney prior to sexual maturation reflects the androgen independence of PS gene expression and suggests that PS (true kallikrein) may play a constitutive and/or developmental role in SMG or renal physiology.
Animals↗
11 beta-hydroxysteroid dehydrogenase and the meaning of life.
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11-beta-Hydroxysteroid Dehydrogenases↗
Serum 5-androstene-3 beta,17 beta-diol sulphate and 5 alpha-androstane-3 alpha,17 beta-diol sulphate in hirsute females with polycystic ovarian disease.
Serum sulphates of 5-androstene-3 beta,17 beta-diol (5-ADIOL-S), 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-DIOL-S) and dehydroepiandrosterone (DHEA-S), unconjugated androstene-dione (AD) and testosterone (T), sex hormone binding globulin (SHBG), free androgen index (FAI), 17 alpha-hydroxyprogesterone (17OHP), luteinising hormone (LH) and follicle stimulating hormone (FSH) were measured by specific radioimmunoassay in 28 hirsute women with polycystic ovarian disease (PCO) and in normal women (n = 73). Mean levels of steroids measured were significantly elevated, and SHBG significantly depressed, in the women with PCO with values (mean +/- SE) for 5-ADIOL-S (516 +/- 51 vs 267 +/- 10 nmol/l), 3 alpha-DIOL-S (130 +/- 9 vs 52 +/- 2 nmol/l), DHEA-S (7.3 +/- 0.5 vs 4.4 +/- 0.2 mumol/l), AD (11.3 +/- 1.1 vs 3.4 +/- 0.2 nmol/l), T (3.3 +/- 0.2 vs 1.5 +/- 0.1 nmol/l) and 17OHP (5.1 +/- 0.8 vs 2.8 +/- 0.2 nmol/l). SHBG levels were 31 +/- 2.9 vs 65 +/- 2.5 nmol/l, and the free androgen index [100 x T (nmol/l) divided by (SHBG nmol/l)] was 12.5 +/- 1.4 vs 2.4 +/- 0.1. The mean LH to FSH ratio was also elevated at 2.8 +/- 0.3. These studies suggest that the measurement of 5-ADIOL-S and DHEA-S may indicate adrenal gland involvement in PCO while 3 alpha-DIOL-S appears to be a reflection of peripheral androgen metabolism. A comprehensive biochemical profile of PCO should thus include the analysis of these sulphoconjugates as well as unconjugated steroids.
Adult↗
Oestrogen administration and the expression of the kallikrein gene family in the rat submandibular gland.
Using a series of oligonucleotide probes (18-21 mers) specific for members of the rat kallikrein/tonin (arginyl-esteropeptidase) gene family (PS, S1, S2, S3, K1, P1), we have shown by Northern blot analysis that all six genes are expressed in the submandibular gland (SMG), with PS (true kallikrein) the most abundant in both male and female rats. Though female levels of PS mRNA are similar to that in the male, levels of mRNA from both the kallikrein-like (S1, K1, P1) and tonin (S2)/tonin-like (S3) genes are all substantially lower in the female than in the male rat. In contrast with the oestrogen dependence of anterior pituitary kallikrein (PS) gene expression, oestrogen administration (6 micrograms/day for 8 days) to castrate male or female rats is without effect on PS or S1, S2, S3, K1, P1 mRNA levels in the SMG. These findings suggest a tissue-specificity in the oestrogen regulation of true kallikrein gene expression in the two tissues. In intact male rats, oestrogen administration lowers SMG levels of S1, S2, S3, K1, and P1 but not PS mRNA to castrate levels, presumably by suppression of the pituitary/gonadal axis, consistent with the previously reported androgen dependence of SMG expression of these genes with the exception of PS.
Animals↗
11 beta-hydroxysteroid dehydrogenase activity in the mammary gland.
Levels of 11 beta-hydroxysteroid dehydrogenase activity in mammary gland homogenates from pregnant and lactating Sprague-Dawley rats were determined by incubation with [3H]corticosterone under standard conditions, followed by thin-layer chromatography of incubated media. Enzyme activity was high in virgin and pregnant rats, but fell soon after parturition, suggesting a possible role for this enzyme in the co-ordinate regulation of glucocorticoid effects on milk protein synthesis.
11-beta-Hydroxysteroid Dehydrogenases↗
Apparent mineralocorticoid excess, pseudohypoaldosteronism, and urinary electrolyte excretion: toward a redefinition of mineralocorticoid action.
Patients with apparent mineralocorticoid excess (AME) have low or absent activity of the enzyme 11 beta OH steroid dehydrogenase (11SD), and inappropriately high intrarenal levels of cortisol resulting in Na+ retention and hypertension. Pseudohypoaldosteronism (PHA), in contrast, is characterized by salt wasting despite hyperaldosteronemia, reflecting low or absent mineralocorticoid receptors (MR). Although AME is presumed to reflect inappropriate cortisol occupancy of MR, several features also suggest inappropriate occupancy of glucocorticoid receptors (GR). To test this possibility, we administered carbenoxolone, which is known to block 11SD, to four patients with PHA, and observed marked mineralocorticoid effects, e.g., antinatriuresis and elevated plasma bicarbonate. To further test the possibility that occupancy of renal GR may induce a classical mineralocorticoid response, we administered the highly specific glucocorticoid RU 28362 to adrenalectomized rats and showed that it has profound antinatriuretic effects. Finally, by selectively blocking MR with RU 28318 or GR with RU 38486, we have shown that corticosterone, the physiologic glucocorticoid in rats, has an antinatriuretic effect in adrenalectomized rats via either MR or GR occupancy. Previous studies have clearly shown that MR are inherently nonselective and have equivalent intrinsic affinity for aldosterone, corticosterone, and cortisol. The present studies suggest that this nonselectivity includes the nuclear response element to which either MR or GR may bind to elicit a mineralocorticoid effect, and further underscore the importance of the enzyme 11SD in the specific mineralocorticoid action of aldosterone.
11-beta-Hydroxysteroid Dehydrogenases↗
Plasma C19 steroid sulphate levels and indices of androgen bioavailability in female pattern androgenic alopecia.
Female pattern androgenic alopecia (AA) is a relatively common endocrine abnormality in premenopausal women. However, unlike hirsutism, little is known about the androgen metabolism and plasma C19 steroid sulphate profiles in this disorder. We have therefore measured the plasma levels of dehydroepiandrosterone sulphate (DHEA-S), 5-androstene-3 beta,17 beta-diol sulphate (5-ADIOL-S), 5 alpha-androstane-3 alpha, 17 beta-diol sulphate (3 alpha-DIOL-S), androstenedione (AD), total testosterone (T), free testosterone (FT), sex hormone binding globulin (SHBG), non-SHBG bound T, luteinizing hormone (LH) and follicle stimulating hormone (FSH), and have calculated the free androgen index (FAI): 100 x T (nmol/l) divided by SHBG (nmol/l), in premenopausal women with AA (n = 25-45) and in normal premenopausal women (n = 17-73). While mean plasma concentrations of DHEA-S and T were not significantly different from controls, mean SHBG concentrations were significantly lower (47 +/- 3 vs 64 +/- 3 nmol/l) and the mean free androgen index (4.4 +/- 0.4 vs 2.4 +/- 0.2), and mean concentrations of free testosterone (45 +/- 5 vs 26 +/- 1.4 pmol/l), non-SHBG bound T (0.9 +/- 0.2 vs 0.6 +/- 0.1 nmol/l) and androstenedione (4.3 +/- 0.3 vs 3.4 +/- 0.2 nmol/l) were significantly elevated in women with AA. Furthermore, mean plasma concentrations of 5-ADIOL-S (512 +/- 42 nmol/l) and 3 alpha-DIOL-S (76 +/- 7 nmol/l) were significantly higher than levels found in normal women (272 +/- 12 nmol/l and 52 +/- 2 nmol/l respectively). The nature of the hyperandrogenism associated with AA may thus only be revealed by a comprehensive plasma androgen and androgen sulphate profile, which may explain apparently aberrant data for a given patient. In addition, 5-ADIOL-S and 3 alpha-DIOL-S may serve as excellent plasma markers of both the existence of the disorder and the efficacy of its treatment.
Adolescent↗