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SUMMARY
The competitive protein-binding radioassay (CPB method) of Murphy (1967) has been adapted to determine total cortisol levels in the plasma of the eel, Anguilla anguilla L. Validation of the method for this species depended in part on the development of a chromatographic—fluorimetric technique for eel cortisol, following classical procedures and using radioactive tracers; by this means, the specificity of the CPB method for cortisol in eel plasma was established. Accuracy, precision and sensitivity of the CPB method were also investigated and were shown to be satisfactory.
Plasma total cortisol levels were determined in eels during osmotic adjustments after transfers from fresh water (FW) to sea-water (SW) and vice versa, and from FW to distilled water. Plasma osmotic pressure and/or sodium levels were monitored simultaneously, to follow the progress of osmotic regulation. In only one of the transfer situations did the plasma cortisol level change significantly, showing a marked transitory increase during the first few days after transfer from FW to SW, corresponding to the development and correction of an 'osmotic crisis'. Plasma cortisol levels were the same in eels adapted for long periods to FW and to SW. Plasma cortisol fell to extremely low levels after hypophysectomy.
These results are discussed in the light of the literature on hormonal control of osmoregulatory mechanisms in the eel, with particular emphasis on the role of adrenocorticosteroids in ionic regulation of animals in SW.
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Exposure of the fetus to excess maternal glucocorticoids has been postulated to alter fetal growth and development, and thus provide a possible mechanism for the link between impaired fetal growth and altered postnatal physiology. However, the effects of exposure to excess maternal glucocorticoids on fetal physiology and metabolism in utero have not been described. We therefore studied the effects of chronic maternal cortisol infusion on fetal growth, blood pressure, metabolism and endocrine status in chronically catheterised fetal sheep. We infused hydrocortisone (80 mg/day, n=6) or saline (n=8) for 10 days into the pregnant ewes beginning at 119 days of gestation. Maternal cortisol infusion reduced fetal growth rate by 30% (girth increment 2.9+/-0.3 vs 1.8+/-0.4 mm/day, P=0.03). Maternal cortisol infusion increased fetal heart weight by 15% relative to body weight and increased ventricular wall thickness by 30% in the left and 50% in the right ventricle. The weight of the spleen was reduced by 30% and placental weight reduced by 25%. Fetal blood pressure increased by approximately 10 mmHg (20%) during maternal cortisol infusion. Maternal cortisol infusion did not alter amino-nitrogen concentrations. However, maternal lactate concentrations increased by 80% and fetal lactate concentrations increased by 74% with maternal cortisol infusion, and both maternal and fetal urea concentrations increased by 40%. Circulating maternal IGF-binding protein (IGFBP)-3 levels had increased by 20% by the end of the maternal cortisol infusion. Fetal IGF-I concentrations decreased during cortisol infusion and fetal IGFBP-1 concentrations were negatively correlated with fetal weight (r=-0.76, P=0.02). We conclude that even a modest elevation of maternal cortisol levels affects fetal growth, cardiovascular function, metabolism and endocrine status which may have long-term consequences.
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The present study examined the extent to which the late gestation rise in fetal plasma cortisol influenced adipose tIssue development in the fetus. The effect of cortisol on the abundance of adipose tIssue mitochondrial proteins on both the inner (i.e. uncoupling protein (UCP)1) and outer (i.e. voltage-dependent anion channel (VDAC)) mitochondrial membrane, together with the long and short forms of the prolactin receptor (PRLR) protein and leptin mRNA was determined. Perirenal adipose tIssue was sampled from ovine fetuses to which (i) cortisol (2-3 mg/day for 5 days) or saline was infused up to 127-130 days of gestation, and (ii) adrenalectomised and intact controls at between 142 and 145 days of gestation (term=148 days). UCP1 protein abundance was significantly lower in adrenalectomised fetuses compared with age-matched controls, and UCP1 was increased by cortisol infusion and with gestational age. Adrenalectomy reduced the concentration of the long form of PRLR, although this effect was only significant for the highest molecular weight isoform. In contrast, neither the short form of PRLR, VDAC protein abundance or leptin mRNA expression was significantly affected by gestational age or cortisol status. Fetal plasma triiodothyronine concentrations were increased by cortisol and with gestational age, an affect abolished by adrenalectomy. When all treatment groups were combined, both plasma cortisol and triiodothyronine concentrations were positively correlated with UCP1 protein abundance. In conclusion, an intact adrenal is necessary for the late gestation rise in UCP1 protein abundance but cortisol does not appear to have a major stimulatory role in promoting leptin expression in fetal adipose tIssue. It remains to be established whether effects on UCP1 protein are directly regulated by cortisol alone or mediated by other anabolic fetal hormones such as triiodothyronine.
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ABSTRACT
An enzyme-linked immunosorbent assay has been developed for the direct assay of cortisol in the saliva of man, sheep, calf and pig. The assay is sensitive (∼1 pg), highly specific and reproducible, and has the advantage over radioimmunosassay in being cheaper and quicker to carry out. The relatively-non invasive method of collecting saliva on cotton buds coupled with simple assay equipment provide a good potential for assessing cortisol status in studies on stress and welfare in farm animals as well as the possibility of monitoring cortisol status in mammals generally.
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SUMMARY
Changes in the concentrations of free amino acids in intracellular fluids and blood plasma were measured in rats treated with cortisol. Increasing age raised the concentrations of free amino acids in plasma, while in liver, with the exception of glycine and alanine, decreased concentrations were observed. Cortisol treatment reduced free amino acid levels in plasma and liver which suggested a progressive catabolism of body proteins and increased protein synthesis in the liver. In skeletal muscle of control rats the free amino acid concentrations increased during the experimental period. Cortisol increased the concentration of certain amino acids and decreased that of others due to an increased protein turnover in muscle.
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SUMMARY
Metabolic effects of various doses of cortisol were studied in the young male chick. Inhibition of body growth increased with dose but there was no proportional decrease in food intake. Liver weight and uric acid excretion increased similarly with dose. When the temporal relationships of these effects were compared, there was no correlation between the increase in uric acid excretion and the increase in liver weight. It is therefore concluded that the increase in liver weight and uric acid excretion are not linked to a common effect of cortisol. Liver glycogen deposition was more sensitive to cortisol compared with the other effects.
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SUMMARY
The relation between free cortisol in urine and 'free Δ4·3 keto-11-hydroxycorticosteroids' has been explored by measurements in sixty urine samples. Free cortisol was measured by a method which involved paper chromatography and incorporated an internal isotopic standard to correct for losses. A rapid and simple technique, measuring fluorescence in ethanolic sulphuric acid, was used to determine the free 11-hydroxycorticosteroids. Although there was a good correlation between the two measurements (r = 0·96), the percentage contribution to the free 11-hydroxycorticosteroids made by true cortisol was small (mean 33 %) and varied from 8 to 73 % in different urine samples.
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SUMMARY
The plasma level and percentage of bound cortisol were measured in sixteen African subjects with hypoproteinaemia of varying aetiologies. When compared with a control group it was found that the percentage of the steroid bound was significantly reduced but that the total cortisol level did not differ from that found in the control subjects. This resulted in a significant increase in the absolute level of free cortisol in the hypoproteinaemic subjects. Attention is drawn to the striking similarity between many of the physical and biochemical changes seen in kwashiorkor and those found in Cushing's syndrome.
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SUMMARY
The binding of cortisol to plasma proteins at room temperature (22–25° c) and 37° c has been studied by equilibrium dialysis against 0·9% NaCl and by gel filtration of the dialysed plasma. The rate of dissociation of the cortisol-transcortin complex during gel filtration of plasma from both normal and oestrogen-treated subjects is a rapid process. The difference in the percentage of cortisol bound as determined by the two methods cannot, therefore, give an accurate measurement of the binding due to albumin.
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SUMMARY
The blocking effect of spironolactone ('Aldactone', Searle) has been tested against 100 mg. cortisol, and 0·25 mg. d-aldosterone, given intravenously. The sodium retention induced by either steroid is roughly halved by either a 300 or a 600 mg. dose of spironolactone. The high potassium excretion induced by cortisol is little if at all affected by spironolactone; the acute kaliuretic action of aldosterone is too small and inconstant to permit a clear assessment of blocking action. The implications of the apparent dissociation of the effects of cortisol upon sodium and upon potassium excretion are discussed.