Browsing by Person "Bailey, M. A."

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Development of a highly sensitive ELISA for aldosterone in mouse urine: Validation in physiological and pathophysiological states of aldosterone excess and depletion
(2009-04) Al-Dujaili, Emad A. S.; Mullins, L. J.; Bailey, M. A.; Kenyon, C. J.
Background: Clinical studies have established aldosterone as a critical physiological and pathophysiological factor in salt and water homeostasis, blood pressure control and in heart failure. Genetic and physiological studies of mice are used to model these processes. A sensitive and specific assay for aldosterone is therefore needed to monitor adrenocortical activity in murine studies of renal function and cardiovascular diseases. Methods: Antibodies against aldosterone were raised in sheep as previously described. HRP-Donkey-anti-sheep IgG enzyme tracer was produced in our laboratory using the Lightning-Link HRP technique. Aldosterone ELISA protocol was validated and optimised to achieve the best sensitivity. The assay was validated by analysing the urine of mice collected under various experimental conditions designed to stimulate or suppress aldosterone in the presence of other potentially interfering steroid hormones. Results: Cross-reactivity with the steroids most likely to interfere was minimal: corticosterone = 0.0028%, cortisol = 0.0006%, DOC = 0.0048% except for 5-dihydro-aldosterone = 1.65%. Minimum detection limit of this ELISA was 5.2 pmole/L (1.5 pg/mL). The validity of urinary aldosterone ELISA was confirmed by the excellent correlation between results obtained before and after solvent extraction and HPLC separation step (Y = 1.092X + 0.03, R2 = 0.995, n = 54). Accuracy studies, parallelism and imprecision data were determined and all found to be satisfactory. Using this assay, mean urinary aldosterone levels were (i) approximately 60-fold higher in females than males mice; (ii) increased 6-fold by dietary sodium restriction; (iii) increased 10-fold by ACTH infusion and (iv) reduced by >60% in Cyp11b1 null mice. Conclusion: We describe an ELISA for urinary aldosterone that is suitable for repeated non-invasive measurements in mice. Female aldosterone levels are higher than males. Unlike humans, most aldosterone in mouse urine is not conjugated. Increased levels were noted in response to dietary sodium restriction and ACTH treatment. The sensitivity of the assay is sufficient to detect suppressed levels in mouse models of congenital adrenal hyperplasia. 2009 Elsevier Inc. All rights reserved.
Evaluation of vertebral rotation by ultrasound for the early detection of adolescent idiopathic scoliosis (AIS).
(IOS Press, 1998) Burwell, R. G.; Kirby, Alanah; Aujla, R. K.; Kirk, E. L.; Pratt, R. K.; Bailey, M. A.; Webb, J. K.; Stokes, I. A. F.
Hsd11b2 haploinsufficiency in mice causes salt sensitivity of blood pressure
(2011-03) Bailey, M. A.; Craigie, E.; Livingstone, D. E. W.; Kotelevtsev, K. V.; Al-Dujaili, Emad A. S.; Kenyon, C. J.; Mullins, J. J.
Salt sensitivity of blood pressure is an independent risk factor for cardiovascular morbidity. Mechanistically, abnormal mineralocorticoid action and subclinical renal impairment may blunt the natriuretic response to high sodium intake, causing blood pressure to rise. 11_-Hydroxysteroid dehydrogenase type 2 (11_HSD2) controls ligand access to the mineralocorticoid receptor, and ablation of the enzyme causes severe hypertension. Polymorphisms in HSD11B2 are associated with salt sensitivity of blood pressure in normotensives. In this study, we used mice heterozygote for a null mutation in Hsd11b2 (Hsd11b2) to define the mechanisms linking reduced enzyme activity to salt sensitivity of blood pressure. A high-sodium diet caused a rapid and sustained increase in blood pressure in Hsd11b2 mice but not in wild-type littermates. During the adaptation to high-sodium diet, heterozygotes displayed impaired sodium excretion, a transient positive sodium balance, and hypokalemia. After 21 days of high-sodium feeding, Hsd11b2 mice had an increased heart weight. Mineralocorticoid receptor antagonism partially prevented the increase in heart weight but not the increase in blood pressure. Glucocorticoid receptor antagonism prevented the rise in blood pressure. In Hsd11b2 mice, high-sodium feeding caused suppression of aldosterone and a moderate but sustained increase in corticosterone. This study demonstrates an inverse relationship among 11_HSD2 activity, heart weight, and blood pressure in a clinically important context. Reduced activity causes salt sensitivity of blood pressure, but this does not reflect illicit activation of mineralocorticoid receptors by glucocorticoids. Instead, we have identified a novel interaction among 11_HSD2, dietary salt, and circulating glucocorticoids. 2011 American Heart Association, Inc.
Transcriptional and physiological responses to chronic ACTH treatment by the mouse kidney
(2009-11-17) Dunbar, D. R.; Khaled, H.; Evans, L. C.; Al-Dujaili, Emad A. S.; Mullins, L. J.; Mullins, J. J.; Kenyon, C. J.; Bailey, M. A.
We investigated the effects on urinary steroid and electrolyte excretion and renal gene expression of chronic infusions of ACTH in the mouse. ACTH caused a sustained increase in corticosteroid excretion; aldosterone excretion was only transiently elevated. There was an increase in the excretion of deoxycorticosterone, a weak mineralocorticoid, to levels of physiological significance. Nevertheless, we observed neither antinatriuresis nor kaliuresis in ACTH-treated mice and plasma renin activity was not suppressed. We identified no changes in expression of mineralocorticoid target genes. Water turnover was increased in chronic ACTH-treated mice, as was hematocrit and hypertonicity: volume contraction is consistent with high levels of glucocorticoid. ACTH-treated mice exhibited other signs of glucocorticoid excess, such as enhanced weight gain and involution of the thymus. We identified novel ACTH-induced changes in i) genes involved in vitamin D (Cyp27b1, Cyp24a1, Gc) and calcium metabolism (Sgk, Calb1, Trpv5) associated with calciuria and phosphaturia; ii) genes that would be predicted to desensitize the kidney to glucocorticoid action (Nr3c1, Hsd11b1, Fkbp5) and iii) genes encoding transporters of enzymes systems associated with xenobiotic metabolism and oxidative stress. Although there is evidence that ACTH-induced hypertension is a function of physiological cross talk between glucocorticoids and mineralocorticoids, the present study suggest that the major changes in electrolyte and fluid homeostasis and renal function are attributable to glucocorticoids. The calcium and organic anion metabolism pathways that are affected by ACTH may explain some of the known adverse effects associated with glucocorticoid excess.