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ABSTRACT
Atrial natriuretic factor (ANF) has been shown to increase circulating cortisol levels in cannulated, free-swimming seawater (SW)-adapted flounders. Increases were apparent within 30 min of i.v. injection of human ANF hANF; 10μg/kg bw) and the increase in plasma cortisol was maintained throughout the 5h experimental period. No such increase was observed in vehicle-injected controls. This apparent steroidogenic effect of ANF was supported by an ANF-induced increase in in-vitro secretion of cortisol by interrenal tissue from SW-adapted trout. By contrast hANF had no significant effect on tissue derived from freshwater adapted trout. An ANF-induced increase in plasma cortisol by a direct effect on interrenal steroidogenesis in SW teleosts would be an appropriate response for survival in hypertonic media.
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SUMMARY
The ability of cells from the zona fasciculata and zona reticularis of the horse adrenal cortex to transform [7α-3H]pregnenolone, [4-14C]progesterone, [7α-3H]17α-hydroxypregnenolone and [4-14C]17α-hydroxyprogesterone to cortisol in vitro was investigated.
It was found that: (1) Both types of cell form cortisol from these steroids. (2) The transformation is greater in fascicular cells. (3) The formation of 17α-hydroxyprogesterone from pregnenolone (via either progesterone or 17α-hydroxypregnenolone) is slower that the subsequent formation of cortisol from 17α-hydroxyprogesterone. (4) The formation of 17α-hydroxyprogesterone from 17α-hydroxypregnenolone is rate-limiting in cortisol formation, but is about 2·4 times faster in fascicular than in reticular cells. (5) 17α-Hydroxylation of progesterone is also faster in fascicular than in reticular cells.
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SUMMARY
The quantitative estimation of cortisol and cortisone in ruminant jugular vein plasma using the soda fluorescence reaction on paper is described. For plasma volumes of 50 ml. or less a partial purification of the plasma extract on a florisil column gave a fraction pure enough for paper chromatography and fluorimetry. The method was used to determine plasma concentrations of adrenal steroids in wethers after injections of either ACTH or cortisol acetate. Extracts from 100 ml. or more of plasma required a further step, namely gradient elution chromatography, to give fractions suitable for fluorimetry on paper. Satisfactory recoveries from 100 ml. plasma of 1 μg. and 0·5 μg. cortisone and cortisol were obtained.
The cortisol concentration in pooled bovine plasma was 0·5 μg./100 ml. and that for ovine plasma 1·45 μg./100 ml. In both cases cortisone was just detectable. Corticosterone could not be detected in bovine plasma.
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SUMMARY
The production rate of cortisol based on both the plasma clearance of the hormone (plasma production rate) and the urinary metabolite method (urinary production rate) was simultaneously measured in early or advanced breast cancer patients and in controls. Higher production of the hormone was observed by both these methods in patients with advanced breast cancer.
There was a significant correlation between the plasma production rate of cortisol and its urinary production based on the specific activities of three urinary metabolites, namely, cortisol, tetrahydrocortisol (THF) and tetrahydrocortisone (THE). However, the values obtained for the urinary production rate differed considerably in about one-third of the patients due to differences in the specific activities of THE and THF. It is postulated that, in some cases, there may be a second precursor of urinary THE and THF which contributes significant amounts to the excretion of these metabolites.
No correlation was found between the cortisol production rate and urinary total 17-hydroxycorticosteroids (17-OHCS).
Search for other papers by CY Andersen in
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The so-called free hormone hypothesis predicts that the biological activity of a given steroid correlates with the free protein-unbound concentration rather than with the total concentration (i.e. free plus protein-bound). Cortisol is a glucocorticoid with many diverse functions and the free hormone hypothesis seems to apply well to the observed effects of cortisol. The ovaries express glucocorticoid receptors and are affected by cortisol, but lack the necessary enzymes for cortisol synthesis. Ovarian follicles modulate the biological activity of cortisol by (1) follicular production of especially progesterone and 17 alpha-hydroxy-progesterone which, within the follicle, reach levels that displace cortisol from its binding proteins, in particular, cortisol-binding protein, making it available for biological action and (2) a developmental regulated expression of two types of 11 beta-hydroxysteroid dehydrogenase (i.e. 11 beta-HSD type 1 and type 2), which oppose the action of one another, the 11 beta-HSD type 2 predominantly inactivating cortisol to cortisone, while 11 beta-HSD type 1 reverses this reaction. As a result, a high concentration of cortisol available for biological action is present in the preovulatory follicle just prior to ovulation and it has been suggested that cortisol may function to reduce the inflammatory-like reactions occurring in connection with ovulation. This paper suggests (1) that the function of the oviduct is also affected by the high levels of free cortisol released in preovulatory follicular fluid at ovulation and (2) that formation and function of the corpus luteum benefits from a high local concentration of free cortisol, whereas the surrounding developing follicles may experience negative effects. If this hypothesis proves correct it may describe a new physiological mechanism by which cortisol interacts with the female reproductive organs, showing that the biologically active concentration of a steroid locally can be regulated to serve specific functions.
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ABSTRACT
Episodic and seasonal rhythms of cortisol secretion were evaluated in six adult Eld's deer (Cervus eldi thamin) stags. Plasma cortisol was measured in serial blood samples collected via remote catheterization every 10 min for 10 h within 2 weeks of the summer solstice (21 June), autumn equinox (22 September), winter solstice (21 December) and spring equinox (20 March), and in weekly blood samples collected from sedated stags. Cortisol was secreted episodically at a rate of approximately 0·6 peaks/h. Based on quantitative peak detection analyses of each 10-h data series, no overall seasonal differences (P>0·05) were detected in the number of peaks (mean range, 5·7–6·2), maximal peak height (mean range, 30·1–40·8 nmol/l), mean peak height as per cent increase (mean range, 158–168%), mean interval between peaks (mean range, 80·1–88·6 min), mean peak width (mean range, 55·1–65·1 min) and mean peak area under the curve (mean range, 675–816 nmol/l min). Based on weekly blood sampling, spring cortisol concentrations were elevated (P<0·05) compared with summer and autumn concentrations. However, when mean cortisol concentrations derived from the 10-h quarterly data sets were analysed, no seasonal differences (P>0·05) were detected. The present study represents the first detailed confirmation of episodic cortisol secretion in any cervid. Results (1) indicate that Eld's deer stags lack a distinct seasonal rhythm of cortisol secretion and (2) clearly illustrate the need for frequent blood sampling in fully conscious individuals to ensure accurate assessment of adrenal status in cervids.
Journal of Endocrinology (1993) 138, 41–49
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Abstract
Parturition and fetal organ maturation in sheep are associated with increased activity of the fetal hypothalamic-pituitary-adrenal (HPA) axis during late pregnancy. However, the factors responsible for HPA activation remain unclear. In the fetal pituitary, levels of pro-opiomelanocortin (POMC) mRNA increase, but the numbers of binding sites for corticotrophin-releasing hormone (CRH), and ACTH responsiveness to exogenous CRH decline during the last 20 days of pregnancy. We have examined regulation of CRH binding, pituitary ACTH responsiveness, and levels of POMC mRNA in cultures of adenohypophysial cells from term fetal sheep. After a 4-day stabilization period, output of immunoreactive (ir) ACTH was increased over 48 h in a dose-dependent fashion by both CRH and arginine vasopressin (AVP) but decreased by cortisol. Subsequent output of ir-ACTH to a 3-h challenge with 100 nm CRH was attenuated after pretreatments with CRH, AVP or cortisol; the effect of CRH being greater than that of cortisol or AVP. At the end of 48 h of treatment with CRH, AVP or cortisol, there was a 40–50% reduction in the number of CRH-binding sites, but the levels of POMC mRNA decreased significantly only after cortisol treatment and were not altered significantly by CRH or AVP.
We conclude that under the conditions of these experiments, CRH and AVP increase ir-ACTH output without increasing the level of steady-state POMC mRNA, but may contribute to loss of pituitary responsiveness to CRH by down-regulation of CRH receptor number. Cortisol exerts negative feedback on POMC mRNA and decreases the number of CRH receptors. Thus, any one or all of CRH, AVP and cortisol could be responsible for the decline in CRH binding in the fetal sheep pituitary during late pregnancy. Although CRH and AVP may affect secretion of ir-ACTH, the present results do not support a role for these neuropeptides in affecting the level of POMC mRNA in the fetal sheep pituitary.
Journal of Endocrinology (1994) 143, 199–208
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SUMMARY
The influence of age and sex on the cortisol content of adrenals, liver, kidney, lung, heart, spleen, muscle, cerebrum, brain stem and blood was studied in white guinea-pigs.
In prepuberal animals no significant difference between sexes was found in the cortisol content of different tissues. In adult female animals, the blood cortisol level was significantly higher than in the male animals. Significantly more cortisol was found in kidneys of adult male than of female animals.
In adult guinea-pigs, the cortisol content was lower in every tissue examined, except liver, compared with young animals. These differences were highly significant. In female guinea-pigs the decrease in tissue cortisol content with age was more pronounced than in male animals.
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Abstract
Using indwelling crown–rump length (CRL)-measuring devices, the growth rate of sheep fetuses was monitored during late gestation and after experimental manipulation of fetal plasma cortisol by exogenous infusion and fetal adrenalectomy. In intact control fetuses, the increment in CRL declined progressively during the last 20–25 days of gestation: mean ± s.e.m. values fell from 5·5 ± 0·4 mm/day (n=12) at 21–25 days before delivery to 2·5 ± 0·3 mm/day (n=12) in the last 5 days before birth (P<0·01). These changes closely parallelled the normal prepartum increase in fetal plasma cortisol which rose from 19·3 ±3·3 nmol/l (n=10) at 21–25 days before birth to 177·4 ± 19·0 nmol/l (n=10) in the final 5 days before delivery (P<0·01). When this cortisol surge was prevented by fetal adrenalectomy, there was no decrease in CRL increment towards normal term: mean CRL increment in the 5 days before normal term (4·8 ± 0·6 mm/day, n=5) was similar to that observed at 21–25 days before term (4·7 ± 0·4 mm/day, n=5). At delivery at term, the body weight (4·116 ± 0·280 kg, n=5) and CRL (51·9 ± 1·7 cm, n=5) of the adrenalectomized fetuses were significantly greater than the corresponding values in their sham-operated controls (2·877 ± 0·070 kg and 47·1 ±1·6 cm, n=6, respectively). In contrast with the sham-operated controls, plasma glucose and insulin levels in the adrenal-ectomized fetuses decreased towards term. Infusion of cortisol into the preterm fetus for 5 days increased fetal plasma cortisol to term levels and decreased the CRL increment to a value (1·8 ± 0·5 mm/day, n=8) which was similar to that observed in untreated controls during the last 5 days before spontaneous delivery at term (2·1 ± 0·3 mm/day, n=6). There were no significant alterations in the fetal arterial concentrations of plasma glucose or insulin in response to fetal cortisol infusion. When all the data were combined irrespective of treatment or proximity to delivery, the fetal plasma concentrations of cortisol (P<0·001) and glucose (P<0·04), but not insulin (P>0·05), had a significant effect on the fetal CRL increment measured over 5-day periods during the last 25–30 days of gestation. These findings show that cortisol inhibits growth of the axial skeleton in the sheep fetus during late gestation. They also indicate that the prepartum cortisol surge may be responsible for the normal decline in fetal growth rate observed towards term in this species.
Journal of Endocrinology (1996) 151, 97–105
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It is well known that high levels of glucocorticoids cause osteoporosis and that physiologic levels of growth hormone (GH) are required for normal bone remodeling. It has been suggested that glucocorticoids regulate GH-responses via the regulation of GH-receptor expression. The aim of the present study was to investigate whether cortisol plays a role in the regulation of GH-receptor expression in cultured human osteoblasts. The effect of serum starvation and cortisol on GH-receptor expression was tested in human osteoblast (hOB)-like cells. Serum starvation for 24 h resulted in an increase in GH-receptor mRNA levels (90 +/- 1% over control culture). Cortisol increased GH-receptor mRNA levels in a dose-dependent manner with a maximal effect at 10(-6)M. The stimulating effect of cortisol on GH-receptor mRNA levels was time-dependent, reaching a peak 12 h after the addition of cortisol (126 +/- 29% over control culture) and remaining up to 12 h later. The increase in GH-receptor mRNA levels was accompanied by an increase in 125I-GH binding which reached a maximum at 24 h (196 +/- 87% over control culture). In conclusion, glucocorticoids increase GH-receptor expression in hOB-like cells. Further studies are needed to clarify whether glucocorticoid-induced regulation of the GH-receptor is important in human bone physiology.