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Zola M, Mejlachowicz D, Gregorio R, Naud MC, Jaisser F, Zhao M, Behar-Cohen F. Chronic Systemic Dexamethasone Regulates the Mineralocorticoid/Glucocorticoid Pathways Balance in Rat Ocular Tissues. Int J Mol Sci 2022; 23:ijms23031278. [PMID: 35163201 PMCID: PMC8836134 DOI: 10.3390/ijms23031278] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 01/20/2022] [Accepted: 01/20/2022] [Indexed: 02/04/2023] Open
Abstract
Central serous chorioretinopathy (CSCR) is a retinal disease affecting the retinal pigment epithelium (RPE) and the choroid. This is a recognized side-effect of glucocorticoids (GCs), administered through nasal, articular, oral and dermal routes. However, CSCR does not occur after intraocular GCs administration, suggesting that a hypothalamic-pituitary-adrenal axis (HPA) brake could play a role in the mechanistic link between CSCR and GS. The aim of this study was to explore this hypothesis. To induce HPA brake, Lewis rats received a systemic injection of dexamethasone daily for five days. Control rats received saline injections. Baseline levels of corticosterone were measured by Elisa at baseline and at 5 days in the serum and the ocular media and dexamethasone levels were measured at 5 days in the serum and ocular media. The expression of genes encoding glucocorticoid receptor (GR), mineralocorticoid receptors (MR), and the 11 beta hydroxysteroid dehydrogenase (HSD) enzymes 1 and 2 were quantified in the neural retina and in RPE/ choroid. The expression of MR target genes was quantified in the retina (Scnn1A (encoding ENac-α, Kir4.1 and Aqp4) and in the RPE/choroid (Shroom 2, Ngal, Mmp9 and Omg, Ptx3, Plaur and Fosl-1). Only 10% of the corticosterone serum concentration was measured in the ocular media. Corticosterone levels in the serum and in the ocular media dropped after 5 days of dexamethasone systemic treatment, reflecting HPA axis brake. Whilst both GR and MR were downregulated in the retina without MR/GR imbalance, in the RPE/choroid, both MR/GR and 11β-hsd2/11β-hsd1 ratio increased, indicating MR pathway activation. MR-target genes were upregulated in the RPE/ choroid but not in the retina. The psychological stress induced by the repeated injection of saline also induced HPA axis brake with a trend towards MR pathway activation in RPE/ choroid. HPA axis brake causes an imbalance of corticoid receptors expression in the RPE/choroid towards overactivation of MR pathway, which could favor the occurrence of CSCR.
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Affiliation(s)
- Marta Zola
- Centre de Recherche des Cordeliers, Sorbonne Université, Université de Paris, Inserm, From Physiopathology of Retinal Diseases to Clinical Advances, 75006 Paris, France; (M.Z.); (D.M.); (R.G.); (M.-C.N.); (F.J.); (M.Z.)
- Assistance Publique-Hôpitaux de Paris, Department of Ophthalmology, Ophtalmopôle, Hôpital Cochin, 75014 Paris, France
| | - Dan Mejlachowicz
- Centre de Recherche des Cordeliers, Sorbonne Université, Université de Paris, Inserm, From Physiopathology of Retinal Diseases to Clinical Advances, 75006 Paris, France; (M.Z.); (D.M.); (R.G.); (M.-C.N.); (F.J.); (M.Z.)
| | - Raquel Gregorio
- Centre de Recherche des Cordeliers, Sorbonne Université, Université de Paris, Inserm, From Physiopathology of Retinal Diseases to Clinical Advances, 75006 Paris, France; (M.Z.); (D.M.); (R.G.); (M.-C.N.); (F.J.); (M.Z.)
| | - Marie-Christine Naud
- Centre de Recherche des Cordeliers, Sorbonne Université, Université de Paris, Inserm, From Physiopathology of Retinal Diseases to Clinical Advances, 75006 Paris, France; (M.Z.); (D.M.); (R.G.); (M.-C.N.); (F.J.); (M.Z.)
| | - Frédéric Jaisser
- Centre de Recherche des Cordeliers, Sorbonne Université, Université de Paris, Inserm, From Physiopathology of Retinal Diseases to Clinical Advances, 75006 Paris, France; (M.Z.); (D.M.); (R.G.); (M.-C.N.); (F.J.); (M.Z.)
| | - Min Zhao
- Centre de Recherche des Cordeliers, Sorbonne Université, Université de Paris, Inserm, From Physiopathology of Retinal Diseases to Clinical Advances, 75006 Paris, France; (M.Z.); (D.M.); (R.G.); (M.-C.N.); (F.J.); (M.Z.)
| | - Francine Behar-Cohen
- Centre de Recherche des Cordeliers, Sorbonne Université, Université de Paris, Inserm, From Physiopathology of Retinal Diseases to Clinical Advances, 75006 Paris, France; (M.Z.); (D.M.); (R.G.); (M.-C.N.); (F.J.); (M.Z.)
- Assistance Publique-Hôpitaux de Paris, Department of Ophthalmology, Ophtalmopôle, Hôpital Cochin, 75014 Paris, France
- Correspondence:
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Nizar JM, Shepard BD, Vo VT, Bhalla V. Renal tubule insulin receptor modestly promotes elevated blood pressure and markedly stimulates glucose reabsorption. JCI Insight 2018; 3:95107. [PMID: 30135311 DOI: 10.1172/jci.insight.95107] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 07/03/2018] [Indexed: 12/25/2022] Open
Abstract
Although the cause of hypertension among individuals with obesity and insulin resistance is unknown, increased plasma insulin, acting in the kidney to increase sodium reabsorption, has been proposed as a potential mechanism. Insulin may also stimulate glucose uptake, but the contributions of tubular insulin signaling to sodium or glucose transport in the setting of insulin resistance is unknown. To directly study the role of insulin signaling in the kidney, we generated inducible renal tubule-specific insulin receptor-KO mice and used high-fat feeding and mineralocorticoids to model obesity and insulin resistance. Insulin receptor deletion did not alter blood pressure or sodium excretion in mice on a high-fat diet alone, but it mildly attenuated the increase in blood pressure with mineralocorticoid supplementation. Under these conditions, KO mice developed profound glucosuria. Insulin receptor deletion significantly reduced SGLT2 expression and increased urinary glucose excretion and urine flow. These data demonstrate a direct role for insulin receptor-stimulated sodium and glucose transport and a functional interaction of insulin signaling with mineralocorticoids in vivo. These studies uncover a potential mechanistic link between preserved insulin sensitivity and renal glucose handling in obesity and insulin resistance.
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Affiliation(s)
- Jonathan M Nizar
- Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA
| | - Blythe D Shepard
- Department of Human Science, Georgetown University, Washington, DC
| | - Vianna T Vo
- Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA
| | - Vivek Bhalla
- Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA
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Mohn ES, Kern HJ, Saltzman E, Mitmesser SH, McKay DL. Evidence of Drug-Nutrient Interactions with Chronic Use of Commonly Prescribed Medications: An Update. Pharmaceutics 2018; 10:E36. [PMID: 29558445 PMCID: PMC5874849 DOI: 10.3390/pharmaceutics10010036] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 03/13/2018] [Accepted: 03/16/2018] [Indexed: 12/18/2022] Open
Abstract
The long-term use of prescription and over-the-counter drugs can induce subclinical and clinically relevant micronutrient deficiencies, which may develop gradually over months or even years. Given the large number of medications currently available, the number of research studies examining potential drug-nutrient interactions is quite limited. A comprehensive, updated review of the potential drug-nutrient interactions with chronic use of the most often prescribed medications for commonly diagnosed conditions among the general U.S. adult population is presented. For the majority of the interactions described in this paper, more high-quality intervention trials are needed to better understand their clinical importance and potential consequences. A number of these studies have identified potential risk factors that may make certain populations more susceptible, but guidelines on how to best manage and/or prevent drug-induced nutrient inadequacies are lacking. Although widespread supplementation is not currently recommended, it is important to ensure at-risk patients reach their recommended intakes for vitamins and minerals. In conjunction with an overall healthy diet, appropriate dietary supplementation may be a practical and efficacious way to maintain or improve micronutrient status in patients at risk of deficiencies, such as those taking medications known to compromise nutritional status. The summary evidence presented in this review will help inform future research efforts and, ultimately, guide recommendations for patient care.
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Affiliation(s)
- Emily S Mohn
- Jean Mayer USDA Human Nutrition Research Center on Aging, and Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA 02111, USA.
| | - Hua J Kern
- Nutrition & Scientific Affairs, Nature's Bounty Co., Ronkonkoma, NY 11779, USA.
| | - Edward Saltzman
- Jean Mayer USDA Human Nutrition Research Center on Aging, and Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA 02111, USA.
| | - Susan H Mitmesser
- Nutrition & Scientific Affairs, Nature's Bounty Co., Ronkonkoma, NY 11779, USA.
| | - Diane L McKay
- Jean Mayer USDA Human Nutrition Research Center on Aging, and Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA 02111, USA.
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Johnson RF, Beltz TG, Johnson AK, Thunhorst RL. Effects of fludrocortisone on water and sodium intake of C57BL/6 mice. Am J Physiol Regul Integr Comp Physiol 2015; 309:R247-54. [PMID: 26017491 DOI: 10.1152/ajpregu.00033.2015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 05/21/2015] [Indexed: 11/22/2022]
Abstract
Little is known about steroidal control of thirst- and salt-appetite behaviors of mice. The current study investigates effects of fludrocortisone acetate (FCA), a steroid with potent glucocorticoid and mineralocorticoid effects, on thirst- and salt-appetite responses of C57BL/6 mice. Treatment with FCA produced dose-dependent (5, 10, and 25 mg/kg) increases in both magnitude and duration of water and sodium intake. Chronic elevation of water and saline intake was achieved with daily injections of FCA. Daily injection of FCA, when only 0.9% saline was available, produced a remarkably rapid increase in saline intake. A single injection of FCA stimulated brisk diuresis and natriuresis in fluid-restricted animals. This work is the first to demonstrate copious water drinking by mice in response to FCA. The results are discussed in terms of the possibility that the renal effects of FCA promote increases in water and sodium turnover and thereby, increases in water and sodium ingestion.
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Affiliation(s)
- Ralph F Johnson
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, Iowa
| | - Terry G Beltz
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, Iowa
| | - Alan Kim Johnson
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, Iowa; Department of Health and Human Physiology, University of Iowa, Iowa City, Iowa; Department of Pharmacology, University of Iowa, Iowa City, Iowa; and François M. Abboud Cardiovascular Center, University of Iowa, Iowa City, Iowa
| | - Robert L Thunhorst
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, Iowa; François M. Abboud Cardiovascular Center, University of Iowa, Iowa City, Iowa
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Goodwin JE. Glucocorticoids and the Cardiovascular System. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015. [DOI: 10.1007/978-1-4939-2895-8_13] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Glucocorticoid-induced hypertension. Pediatr Nephrol 2012; 27:1059-66. [PMID: 21744056 DOI: 10.1007/s00467-011-1928-4] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 05/12/2011] [Accepted: 05/13/2011] [Indexed: 10/18/2022]
Abstract
Glucocorticoid-induced hypertension is a common clinical problem that is poorly understood, thus rendering treatment strategies sub-optimal. This form of hypertension has been commonly thought to be mediated by excess sodium and water reabsorption by the renal mineralocorticoid receptor. However, experimental and clinical data in both humans and animal models suggest important roles for the glucocorticoid receptor as well, in both the pathogenesis and maintenance of this hypertension. The glucocorticoid receptor is widely expressed in a number of organ systems relevant to blood pressure regulation, including the kidney, the brain and the vasculature. In vitro studies in isolated kidney tissues as well as in vascular smooth muscle and vascular endothelial cells have attempted to elucidate the molecular physiology of glucocorticoid-induced hypertension, but have generally been limited by the inability to study signaling pathways in an intact organism. More recently, the power of mouse genetics has been employed to examine the tissue-specific contributions of vascular and extra-vascular tissues to this form of hypertension. Here we review recent developments in our understanding of the pathogenesis of glucocorticoid-induced hypertension.
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Knockout of the vascular endothelial glucocorticoid receptor abrogates dexamethasone-induced hypertension. J Hypertens 2011; 29:1347-56. [PMID: 21659825 DOI: 10.1097/hjh.0b013e328347da54] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
BACKGROUND Glucocorticoid-mediated hypertension is incompletely understood. Recent studies have suggested the primary mechanism of this form of hypertension may be through the effects of glucocorticoids on vascular tissues and not to excess sodium and water re-absorption as traditionally believed. OBJECTIVE The goal of this study was to better understand the role of the vasculature in the generation and maintenance of glucocorticoid-mediated hypertension. METHODS We created a mouse model with a tissue-specific knockout of the glucocorticoid receptor in the vascular endothelium. RESULTS We show that these mice are relatively resistant to dexamethasone-induced hypertension. After 1 week of dexamethasone treatment, control animals have a mean blood pressure (BP) increase of 13.1 mmHg, whereas knockout animals have only a 2.7 mmHg increase (P < 0.001). Interestingly, the knockout mice have slightly elevated baseline BP compared with the controls (112.2 ± 2.5 vs. 104.6 ± 1.2 mmHg, P = 0.04), a finding which is not entirely explained by our data. Furthermore, we demonstrate that the knockout resistance arterioles have a decreased contractile response to dexamethasone with only 6.6% contraction in knockout vessels compared with 13.4% contraction in control vessels (P = 0.034). Finally, we show that in contrast to control animals, the knockout animals are able to recover a significant portion of their normal circadian BP rhythm, suggesting that the vascular endothelial glucocorticoid receptor may function as a peripheral circadian clock. CONCLUSION Our study highlights the importance of the vascular endothelial glucocorticoid receptor in several fundamental physiologic processes, namely BP homeostasis and circadian rhythm.
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Abstract
Over the 70 or so years since their discovery, there has been continuous interest and activity in the field of corticosteroid functions. However, despite major advances in the characterisation of receptors and coregulators, in some ways we still lack clear insight into the mechanism of receptor activation, and, in particular, the relationship between steroid hormone structure and function remains obscure. Thus, why should deoxycorticosterone (DOC) reportedly be a weak mineralocorticoid, while the addition of an 11β-hydroxyl group produces glucocorticoid activity, yet further hydroxylation at C18 leads to the most potent mineralocorticoid, aldosterone? This review aims to show that the field has been confused by the misreading of the earlier literature and that DOC, far from being relatively inactive, in fact has a wide range of activities not shared by the other corticoids. In contrast to the accepted view, the presence of an 11β-hydroxyl group yields, in corticosterone or cortisol, hormones with more limited functions, and also more readily regulated, by 11β-hydroxysteroid dehydrogenase. This interpretation leads to a more systematic understanding of structure-function relationships in the corticosteroids and may assist more rational drug design.
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Affiliation(s)
- Gavin P Vinson
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK.
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Unwin RJ, Luft FC, Shirley DG. Pathophysiology and management of hypokalemia: a clinical perspective. Nat Rev Nephrol 2011; 7:75-84. [PMID: 21278718 DOI: 10.1038/nrneph.2010.175] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Potassium (K(+)) ions are the predominant intracellular cations. K(+) homeostasis depends on external balance (dietary intake [typically 100 mmol per day] versus excretion [95% via the kidney; 5% via the colon]) and internal balance (the distribution of K(+) between intracellular and extracellular fluid compartments). The uneven distribution of K(+) across cell membranes means that a mere 1% shift in its distribution can cause a 50% change in plasma K(+) concentration. Hormonal mechanisms (involving insulin, β-adrenergic agonists and aldosterone) modulate K(+) distribution by promoting rapid transfer of K(+) across the plasma membrane. Extrarenal K(+) losses from the body are usually small, but can be marked in individuals with chronic diarrhea, severe burns or prolonged sweating. Under normal circumstances, the kidney's distal nephron secretes K(+) and determines final urinary excretion. In patients with hypokalemia (plasma K(+) concentration <3.5 mmol/l), after the exclusion of extrarenal causes, alterations in sodium ion delivery to the distal nephron, mineralocorticoid status, or a specific inherited or acquired defect in distal nephron function (each of which affects distal nephron K(+) secretion), should be considered. Clinical management of hypokalemia should establish the underlying cause and alleviate the primary disorder. This Review aims to inform clinicians about the pathophysiology and appropriate treatment for hypokalemia.
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Affiliation(s)
- Robert J Unwin
- Centre for Nephrology, Royal Free Hospital, University College London, Rowland Hill Street, London NW3 2PF, UK.
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Goodwin JE, Zhang J, Velazquez H, Geller DS. The glucocorticoid receptor in the distal nephron is not necessary for the development or maintenance of dexamethasone-induced hypertension. Biochem Biophys Res Commun 2010; 394:266-71. [PMID: 20188070 DOI: 10.1016/j.bbrc.2010.02.123] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 02/19/2010] [Indexed: 10/19/2022]
Abstract
Glucocorticoids are used as a treatment for a variety of conditions and hypertension is a well-recognized side effect of their use. The mechanism of glucocorticoid-induced hypertension is incompletely understood and has traditionally been attributed to promiscuous activation of the mineralocorticoid receptor by cortisol. Multiple lines of evidence, however, point to the glucocorticoid receptor as an important mediator as well. We have developed a mouse model of glucocorticoid-induced hypertension, which is dependent on the glucocorticoid receptor. To determine the site(s) of glucocorticoid receptor action relevant to the development of hypertension, we studied glucocorticoid-induced hypertension in a mouse with a tissue-specific knockout of the glucocorticoid receptor in the distal nephron. Although knockout mice had similar body weight, nephron number and renal histology compared to littermate controls, their baseline blood pressure was mildly elevated. Nevertheless, distal nephron glucocorticoid receptor knockout mice and controls had a similar hypertensive response to dexamethasone. Urinary excretion of electrolytes, both before and after administration of glucocorticoid was also indistinguishable between the two groups. We conclude that the glucocorticoid receptor in the distal nephron is not necessary for the development or maintenance of dexamethasone-induced hypertension in our model.
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Affiliation(s)
- Julie E Goodwin
- Section of Nephrology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT, USA.
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Greenlee M, Wingo CS, McDonough AA, Youn JH, Kone BC. Narrative review: evolving concepts in potassium homeostasis and hypokalemia. Ann Intern Med 2009; 150:619-25. [PMID: 19414841 PMCID: PMC4944758 DOI: 10.7326/0003-4819-150-9-200905050-00008] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Humans are intermittently exposed to large variations in potassium intake, which range from periods of fasting to ingestion of potassium-rich meals. These fluctuations would abruptly alter plasma potassium concentration if not for rapid mechanisms, primarily in skeletal muscle and the liver, that buffer the changes in plasma potassium concentration by means of transcellular potassium redistribution and feedback control of renal potassium excretion. However, buffers have capacity limits, and even robust feedback control mechanisms require that the perturbation occur before feedback can initiate corrective action. In contrast, feedforward control mechanisms sense the effect of disturbances on the system's homeostasis. This review highlights recent experimental insights into the participation of feedback and feedforward control mechanisms in potassium homeostasis. New data make clear that feedforward homeostatic responses activate when decreased potassium intake is sensed, even when plasma potassium concentration is still within the normal range and before frank hypokalemia ensues, in addition to the classic feedback activation of renal potassium conservation when plasma potassium concentration decreases. Given the clinical importance of dyskalemias in patients, these novel experimental paradigms invite renewed clinical inquiry into this important area.
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Affiliation(s)
- Megan Greenlee
- University of Florida College of Medicine and Department of Veterans Affairs Medical Center, Gainesville, Florida 32610, USA
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Abstract
Practical relevance Inflammatory bowel disease (IBD) is a common diagnosis in cats with chronic gastrointestinal signs. Its management presents clinical challenges, not least because rational therapy relies on a definitive diagnosis, and current understanding of the underlying pathogenesis has, to date, limited the development of specific therapies. The mainstays of treatment remain dietary manipulation and immunosuppressive therapy, but treatment failures are not uncommon. A logical clinical approach is important and there are a number of alternative or adjunctive treatments that can prove useful in refractory cases. Evidence base This article draws on data from clinical trials in humans, in vitro studies, prospective and retrospective studies in cats with naturally occurring IBD, and clinical experience to discuss the work-up and treatment selection for cats with idiopathic IBD. Patient group IBD affects young adult to geriatric cats of both sexes. Audience Companion animal and feline practitioners are at the front line when it comes to managing these often challenging cases.
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Affiliation(s)
- Lauren Trepanier
- University of Wisconsin-Madison, School of Veterinary Medicine, Madison, WI, USA.
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Goodwin JE, Zhang J, Geller DS. A critical role for vascular smooth muscle in acute glucocorticoid-induced hypertension. J Am Soc Nephrol 2008; 19:1291-9. [PMID: 18434569 DOI: 10.1681/asn.2007080911] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Although glucocorticoid (GC)-induced hypertension has commonly been attributed to promiscuous activation of the mineralocorticoid receptor by cortisol, thereby promoting excess reabsorption of sodium and water, numerous lines of evidence indicate that this is not the only or perhaps even the primary mechanism. GC induce a number of effects on vascular smooth muscle (VSM) in vitro that may be pertinent to hypertension, but their contribution in vivo is unknown. To address this question, a mouse model with a tissue-specific knockout (KO) of the GC receptor in the VSM was created and characterized. Similar to control mice, KO mice exhibited normal baseline BP and, interestingly, showed normal circadian variation in BP. When dexamethasone was administered, however, the acute hypertensive response was markedly attenuated in KO mice, and there was a trend toward a decreased chronic hypertensive response. These data suggest that the GC receptor in VSM plays a critical role in the acute hypertensive response to GC in vivo.
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Affiliation(s)
- Julie E Goodwin
- Section of Nephrology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT 06520-8029, USA
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Geerling JC, Loewy AD. Aldosterone-sensitive neurons in the nucleus of the solitary tract: Efferent projections. J Comp Neurol 2006; 497:223-50. [PMID: 16705681 DOI: 10.1002/cne.20993] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The nucleus of the solitary tract (NTS) contains a subpopulation of neurons that express the enzyme 11-beta-hydroxysteroid dehydrogenase type 2 (HSD2), which makes them uniquely sensitive to aldosterone. These neurons may drive sodium appetite, which is enhanced by aldosterone. Anterograde and retrograde neural tracing techniques were used to reveal the efferent projections of the HSD2 neurons in the rat. First, the anterograde tracer Phaseolus vulgaris leucoagglutinin was used to label axonal projections from the medial NTS. Then, NTS-innervated brain regions were injected with a retrograde tracer, cholera toxin beta subunit, to determine which sites are innervated by the HSD2 neurons. The HSD2 neurons project mainly to the ventrolateral bed nucleus of the stria terminalis (BSTvl), the pre-locus coeruleus (pre-LC), and the inner division of the external lateral parabrachial nucleus (PBel). They also send minor axonal projections to the midbrain ventral tegmental area, lateral and paraventricular hypothalamic nuclei, central nucleus of the amygdala, and periaqueductal gray matter. The HSD2 neurons do not innervate the ventrolateral medulla, a key brainstem autonomic site. Additionally, our tracing experiments confirmed that the BSTvl receives direct axonal projections from the neighboring A2 noradrenergic neurons in the NTS, and from the same pontine sites that receive major inputs from the HSD2 neurons (PBel and pre-LC). The efferent projections of the HSD2 neurons may provide new insights into the brain circuitry responsible for sodium appetite.
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Affiliation(s)
- Joel C Geerling
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Da Silva JAP, Jacobs JWG, Kirwan JR, Boers M, Saag KG, Inês LBS, de Koning EJP, Buttgereit F, Cutolo M, Capell H, Rau R, Bijlsma JWJ. Safety of low dose glucocorticoid treatment in rheumatoid arthritis: published evidence and prospective trial data. Ann Rheum Dis 2005; 65:285-93. [PMID: 16107513 PMCID: PMC1798053 DOI: 10.1136/ard.2005.038638] [Citation(s) in RCA: 307] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Adverse effects of glucocorticoids have been abundantly reported. Published reports on low dose glucocorticoid treatment show that few of the commonly held beliefs about their incidence, prevalence, and impact are supported by clear scientific evidence. Safety data from recent randomised controlled clinical trials of low dose glucocorticoid treatment in RA suggest that adverse effects associated with this drug are modest, and often not statistically different from those of placebo.
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Affiliation(s)
- J A P Da Silva
- Reumatologia, Hospitais da Universidade, 3000-075 Coimbra, Portugal.
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Marissal-Arvy N, Mormède P. Excretion of electrolytes in Brown Norway and Fischer 344 rats: effects of adrenalectomy and of mineralocorticoid and glucocorticoid receptor ligands. Exp Physiol 2004; 89:753-65. [PMID: 15364879 DOI: 10.1113/expphysiol.2004.028621] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Our previous studies showed that adrenalectomy (ADX) has surprisingly no effect on body weight and fluid intake in the Brown Norway rat strain, suggesting that mineralocorticoid receptor (MR)-mediated effects are present even in absence of corticosteroids in this strain. Moreover, glucocorticoid receptor (GR)-mediated mechanisms are more effective in Brown Norway than in Fischer 344 rats. Such functional differences in corticosteroid receptor pathways between Brown Norway and Fischer 344 rats led us to compare the effect of ADX and MR/GR-mediated actions on sodium and potassium excretion between these two rat strains. To this end, we first measured the effect of an acute high dose of aldosterone on the urinary Na+/K+ concentration ratio in intact and ADX Brown Norway and Fischer 344 rats. Second, to discriminate mineralocorticoid from glucocorticoid actions, we treated chronically ADX rats with increasing doses of aldosterone or RU28362, a pure GR agonist, in the drinking fluid. As sodium homeostasis involves salt appetite regulation, behaviour under mineralocorticoid control, we also measured saline preference in Brown Norway and Fischer 344 rats. Our data illustrate: (1) the very limited effect of ADX on body weight, food and fluid intake, diuresis, natriuresis, kaliuresis and salt appetite in Brown Norway rats, supporting the presence of MR signalling pathways in the absence of adrenal steroids in these rats; (2) the insensitivity of MR to aldosterone in intact Brown Norway rats, and the reduced sensitivity of MR to aldosterone in ADX Brown Norway rats compared with ADX Fischer 344 rats; and (3) the greater sensitivity of GR-related mechanisms to RU28362 in Brown Norway than in Fischer 344 rats in terms of body weight gain and electrolyte excretion. Considering that both MRs and GRs regulate hypothalamic-pituitary-adrenal axis processes, such functional differences in corticosteroid receptors could be at the origin, at least partly, of the strain differences in corticotropic activity/reactivity to stress previously described.
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Affiliation(s)
- Nathalie Marissal-Arvy
- Neurogénétique et Stress, INSERM U471 - INRA UMR1243 - Université de Bordeaux 2, Institut François Magendie de Neurosciences, 1, rue Camille Saint Saëns, 33077 Bordeaux Cedex, France.
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Abstract
Aldosterone regulates renal sodium reabsorption through binding to the mineralocorticoid receptor (MR). Because the glucocorticoid receptor (GR) is expressed together with the MR in aldosterone target cells, glucocorticoid hormones bound to GR may also intervene to modulate physiological functions in these cells. In addition, each steroid can bind both receptors, and the MR has equal affinity for aldosterone and glucocorticoid hormones. Several cellular and molecular mechanisms intervene to allow specific aldosterone regulatory effects, despite the large prevalence of glucocorticoid hormones in the plasma. They include the local metabolism of the glucocorticoid hormones into inactive derivatives by the enzyme 11beta-hydroxysteroid dehydrogenase; the intrinsic properties of the MR that discriminate between ligands through differential contacts; the possibility of forming homo- or heterodimers between MR and GR, leading to differential transactivation properties; and the interactions of MR and GR with other regulatory transcription factors. The relative contribution of each of these successive mechanisms may vary among aldosterone target cells (epithelial vs. nonepithelial) and according to the hormonal context. All these phenomena allow fine tuning of cellular functions depending on the degree of cooperation between corticosteroid hormones and other factors (hormonal or tissue specific). Such interactions may be altered in pathophysiological situations.
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Affiliation(s)
- N Farman
- Institut National de la Santé et de la Recherche Médicale U-478, Faculté de Médecine X. Bichat-Institut Fédératif de Recherches 02, 75870 Paris Cedex 18, France.
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Féraille E, Doucet A. Sodium-potassium-adenosinetriphosphatase-dependent sodium transport in the kidney: hormonal control. Physiol Rev 2001; 81:345-418. [PMID: 11152761 DOI: 10.1152/physrev.2001.81.1.345] [Citation(s) in RCA: 340] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Tubular reabsorption of filtered sodium is quantitatively the main contribution of kidneys to salt and water homeostasis. The transcellular reabsorption of sodium proceeds by a two-step mechanism: Na(+)-K(+)-ATPase-energized basolateral active extrusion of sodium permits passive apical entry through various sodium transport systems. In the past 15 years, most of the renal sodium transport systems (Na(+)-K(+)-ATPase, channels, cotransporters, and exchangers) have been characterized at a molecular level. Coupled to the methods developed during the 1965-1985 decades to circumvent kidney heterogeneity and analyze sodium transport at the level of single nephron segments, cloning of the transporters allowed us to move our understanding of hormone regulation of sodium transport from a cellular to a molecular level. The main purpose of this review is to analyze how molecular events at the transporter level account for the physiological changes in tubular handling of sodium promoted by hormones. In recent years, it also became obvious that intracellular signaling pathways interacted with each other, leading to synergisms or antagonisms. A second aim of this review is therefore to analyze the integrated network of signaling pathways underlying hormone action. Given the central role of Na(+)-K(+)-ATPase in sodium reabsorption, the first part of this review focuses on its structural and functional properties, with a special mention of the specificity of Na(+)-K(+)-ATPase expressed in renal tubule. In a second part, the general mechanisms of hormone signaling are briefly introduced before a more detailed discussion of the nephron segment-specific expression of hormone receptors and signaling pathways. The three following parts integrate the molecular and physiological aspects of the hormonal regulation of sodium transport processes in three nephron segments: the proximal tubule, the thick ascending limb of Henle's loop, and the collecting duct.
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Affiliation(s)
- E Féraille
- Division of Nephrology, Geneva University Hospital, Geneva, Switzerland.
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Abstract
The mammalian collecting duct plays a dominant role in regulating K(+) excretion by the nephron. The collecting duct exhibits axial and intrasegmental cell heterogeneity and is composed of at least two cell types: collecting duct cells (principal cells) and intercalated cells. Under normal circumstances, the collecting duct cell in the cortical collecting duct secretes K(+), whereas under K(+) depletion, the intercalated cell reabsorbs K(+). Assessment of the electrochemical driving forces and of membrane conductances for transcellular and paracellular electrolyte movement, the characterization of several ATPases, patch-clamp investigation, and cloning of the K(+) channel have provided important insights into the role of pumps and channels in those tubule cells that regulate K(+) secretion and reabsorption. This review summarizes K(+) transport properties in the mammalian collecting duct. Special emphasis is given to the mechanisms of how K(+) transport is regulated in the collecting duct.
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Affiliation(s)
- S Muto
- Department of Nephrology, Jichi Medical School, Minamikawachi, Tochigi, Japan.
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Abstract
Aldosterone plays a major role in the regulation of renal sodium reabsorption, of extracellular fluid volume and blood pressure. Such specific mineralocorticoid physiological adaptations occur despite the large prevalence of glucocorticoid hormones over aldosterone in the plasma. Indeed both classes of hormones bind with the same affinity to the mineralocorticoid receptor, but several mechanisms allow selective and tissue-specific aldosterone effects. They represent a series of mutually interacting selectivity filters, which have not yet been fully documented. The main determinants of aldosterone selective effects include an enzymatic protection of the mineralocorticoid receptor, the intrinsic properties of the mineralocorticoid receptor towards different ligands, and numerous possibilities of interaction between corticosteroid receptors (forming different homo or heterodimers) and other transcription factors.
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Affiliation(s)
- N Farman
- INSERM U478, Faculté de Medecine X. Bichat, Institut Fédératif de recherches Cellules Epithéliales, Paris, France.
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21
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Abstract
The presently accepted regulators of the homeostatic excretion of potassium are the plasma concentrations of aldosterone and potassium. Evidence for a role of aldosterone is reviewed, and it is pointed out that aldosterone is kaliuretic at supraphysiologic levels but has little kaliuretic activity within its normal secretory range. Elevation of plasma potassium above its normal range enhances the kaliuretic action of aldosterone. Elevation of plasma potassium above, but not within, its normal range is strongly kaliuretic. In sheep the kaliuresis induced by intake of a potassium rich meal cannot be explained by changes in aldosterone or plasma potassium. A kaliuretic reflex arising from receptors in the gut, portal vein or liver has been proposed the explain the meal-induced kaliuresis. This putative reflex involves the central nervous system and efferent kaliuretic factors other than aldosterone and plasma potassium. Evidence for the involvement of the central nervous system and undetermined kaliuretic regulatory factors can be found in studies of the physiologic circadian rhythm of renal potassium excretion. This rhythmic excretion does not appear to depend on changes in either aldosterone or plasma potassium.
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Affiliation(s)
- L Rabinowitz
- Department of Human Physiology, University of California, Davis, USA
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22
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Morris DJ. The role of steroid metabolism in protective and specificity conferring mechanisms of mineralocorticoid action. VITAMINS AND HORMONES 1995; 50:461-85. [PMID: 7709604 DOI: 10.1016/s0083-6729(08)60660-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- D J Morris
- Department of Pathology and Laboratory Medicine, Miriam Hospital, Providence, Rhode Island
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van Buren M, Rabelink TJ, Koppeschaar HP, Koomans HA. Role of glucocorticoid in excretion of an acute potassium load in patients with Addison's disease and panhypopituitarism. Kidney Int 1993; 44:1130-8. [PMID: 8264146 DOI: 10.1038/ki.1993.359] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Glucocorticoid (GC) has been shown to stimulate potassium (K) excretion in various conditions, but it is still incompletely resolved whether its presence is essential for the normal K homeostasis. We addressed this question in patients with selective GC deficiency (panhypopituitarism) and with combined GC and mineralocorticoid deficiency (Addison's disease), studied 24 hours after withdrawal of their regular substitution therapy. Compared to data in healthy subjects, both basal K excretion and the kaliuresis after a KCl load (1 mmol/kg body wt orally) were impaired in either patient group (P < 0.05). Physiological cortisol supplementation (20 mg 3 hr prior to test, and 1 mg/hr during test) increased basal K excretion (from 10.6 +/- 1.8 to 19.2 +/- 1.9 mmol/5 hr, P < 0.01) and KCl stimulated kaliuresis (from 47.9 +/- 6.1 to 54.8 +/- 4.7 mmol/5 hr, P = 0.06) to normal levels in panhypopituitarism. Cortisol also improved basal K excretion (from 10.2 +/- 1.5 to 16.9 +/- 3.5 mmol/5 hr, P < 0.05) and KCl-stimulated K excretion (from 31.6 +/- 2.5 to 45.2 +/- 3.8 mmol/5 hr, P < 0.05) in Addison's disease, although KCl-stimulated K excretion remained below normal (P < 0.01). The effects of cortisol on sodium excretion differed between the two patient groups (P < 0.05) in that only in Addison's disease the improved K excretion was associated with sodium retention. Additional experiments with the purely GC compound dexamethasone (0.5 mg 3 hr prior to test, and 0.03 mg/hr during test) in the patients with Addison's disease also improved K excretion (P < 0.05), but without the concomitant sodium retention observed after cortisol.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M van Buren
- Department of Nephrology & Hypertension, and Endocrinology, University Hospital Utrecht, The Netherlands
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24
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25
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Marver D. Corticosteroids and the Kidney. Compr Physiol 1992. [DOI: 10.1002/cphy.cp080232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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26
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Abstract
(1) Decreased 11 beta-OHSD activity permits binding of cortisol to the Type I (mineralocorticoid) receptor in humans, thereby producing spironolactone-inhibitable Na+ retention, hypokalemia and hypertension, the syndrome of apparent mineralocorticoid excess (AME). (2) Blockade of either the Type I receptor with spironolactone or the Type II (glucocorticoid) receptor with RU-486 does not consistently abolish the effects of stress level cortisol on Na+ retention and hypertension in acute studies in normal humans, suggesting the existence of an additional glucocorticoid receptor. (3) Enhanced glucocorticoid 6 beta-hydroxylation could play an etiologic role in certain hypertensive syndromes. (4) Both decreased 11 beta-OHSD and increased 6 beta-OHase are candidates as intermediate phenotypes for the remote phenotype essential hypertension.
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Affiliation(s)
- J Crabbé
- Department of Physiology, UCL Medical School, Brussels, Belgium
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Egfjord M, Daugaard H, Olgaard K. Influence of glucocorticoid on the metabolism of aldosterone in the isolated perfused rat liver and kidney. Steroids 1992; 57:335-43. [PMID: 1412571 DOI: 10.1016/0039-128x(92)90053-c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The effect of glucocorticoid deficiency and excess on the extraadrenal metabolism of D-[4-14C]aldosterone (at 4 nM) was studied by radioimmunoassay and by high-performance liquid chromatography in the isolated perfused liver and kidney of adult Wistar rats. Bilateral adrenalectomy was performed 3 weeks before experiments. In nonadrenalectomized rats, 0.3 mg/kg/day dexamethasone was continuously infused subcutaneously for 1 week before experiments. Adrenalectomy did not affect hepatic or renal metabolism of aldosterone. Dexamethasone treatment did not change the renal handling of aldosterone. However, the hepatic clearance of aldosterone was 19% lower (P less than 0.05) in livers of dexamethasone treated rats than in livers of normal rats. After 5 minutes, perfusate [4-14C]aldosterone metabolites were lower in livers of dexamethasone-treated than in livers of normal rats (P less than 0.05). Similar perfusate levels were then obtained. Radiometabolite peaks with similar relative retention times were found in the hepatic perfusate of all groups. However, the ratio between circulating polar metabolites of aldosterone and the metabolites less polar than tetrahydroaldosterone, after 5 and 15 minutes, was highest in livers of dexamethasone-treated rats. Biliary elimination of 14C was similar in all groups. Significant amounts of conjugated tetrahydroaldosterone were only excreted in the bile of dexamethasone-treated rats. In conclusion, glucocorticoid excess reduced the hepatic clearance of aldosterone and changed the pattern of the hepatic metabolites of aldosterone both in circulation and in bile.
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Affiliation(s)
- M Egfjord
- Medical Department P, Rigshospitalet, University of Copenhagen, Denmark
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29
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Abstract
Mineralocorticoid hormones are a subset of steroid hormones that act primarily in epithelial tissues to regulate ion transport of Na+, K+ and H+. Cellular specificity is conferred by receptors which act in the nucleus to stimulate gene expression. Transcription and subsequent translation result in the production of new proteins which mediate the physiologic effects. The mechanisms involved in receptor specificity and localization, in regulation of gene activation, and in expression of transport effects are reviewed. The cellular actions of mineralocorticoids fit well with the general model of steroid hormone action but considerable questions remain at each step in the process.
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Affiliation(s)
- J P Johnson
- Department of Nephrology, Walter Reed Army Institute of Research, Washington D.C. 20307
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30
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31
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Watlington CO, Atkins JL, McNeil JS, Grogan WM, Johnson JP. Corticosterone is converted to 6 beta-hydroxycorticosterone in rat: effects of the metabolite on urinary electrolyte excretion. JOURNAL OF STEROID BIOCHEMISTRY 1988; 31:947-54. [PMID: 3199831 DOI: 10.1016/0022-4731(88)90337-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
This study was performed to determine whether corticosterone (B), the major glucocorticoid of rat, is metabolized to its 6 beta-OH derivative (6 beta-OH-B) and whether this derivatives has any effects on Na+ or K+ transport in rat kidney. Normal and adrenalectomized (adx) rats were injected with [3H]B and urine was collected for 5 h and examined for metabolites of B. Metabolites were collected by solid phase extraction on mu Bondapak C18 cartridges and fractionated by reversed phase high performance liquid chromatography. Fractions coeluting with 6 beta-OH-B were rechromatographed by normal phase thin layer chromatography. Approximately 5% of the radioactivity recovered from the urine of both intact and adx rats cochromatographed with 6 beta-OH-B on the two systems. Mass spectra of this fraction were virtually identical to those of authentic 6 beta-OH-B, demonstrating that rats do metabolize B to its 6 beta-OH derivative. To evaluate the biological activity of this metabolite, adx rats were injected with NaCl and KCl and with varying dosage of either 6 beta-OH-B or reference steroids (aldosterone, B, 6 beta-OH-F). 6 beta-OH-B produced a significant antinatriuresis at all doses. Kaliuresis occurred only at the highest dose and creatinine excretion increased, suggesting increased glomerular filtration from a glucocorticoid effect. Although 6 beta-OH-B may simply be exerting mineralo- and glucocorticoid actions there are two unexplained findings. First, 6 beta-OH-B (10 micrograms/100 g) significantly decreased urinary K excretion with associated antinatriuresis, an effect which has not been seen with Aldo administration. Second, neither a kaliuretic nor antinatriuretic effect of 6 beta-OH-B could be demonstrated in experiments using a method to enhance mineralocorticoid induced K+ excretion (K+ deprivation and NaCl loading only). Yet, the dose used was clearly antinatriuretic in the initial bioassay. It is concluded that the rat is capable of metabolizing B to its 6 beta-OH-B derivative which appears in substantial quantity in the urine. This metabolite produces antinatriuresis in the adrenalectomized rat.
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Affiliation(s)
- C O Watlington
- Department of Medicine, Medical College of Virginia/VCU, Richmond 23298
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32
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Adam WR, Adams BA, Ellis AG. In vivo estimation of changes in distal tubule flow and their role in dexamethasone-induced kaliuresis in control and potassium-adapted rats. Clin Exp Pharmacol Physiol 1987; 14:47-57. [PMID: 3608240 DOI: 10.1111/j.1440-1681.1987.tb00956.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The aim of this study was to determine whether the kaliuresis associated with glucocorticoids is due to a direct tubular action or is secondary to effects of glucocorticoids on distal tubule flow. A whole kidney technique was used to avoid the problem, inherent in microperfusion and micropuncture studies, of deciding whether (all) the appropriate nephron segment(s) are being studied. The method used was to determine the best whole kidney measure of distal tubule flow (the independent variable) by correlating this with the dependent variable (potassium excretion, corrected for differences in plasma potassium, UkV/PIK+) in conscious intact and adrenalectomized control and potassium-adapted rats. After an intragastric potassium chloride load, the correlation of UkV/PIK+ with UkV + UNaV was better than with either UNaV or UV, as measures of distal tubule flow. From the relationship a measure of potassium excretion independent of distal tubule flow can thus be calculated as UkV/PIK+ divided by (UkV + UNaV), defined as UK#. Measurement of UK# clearly demonstrates decreases in potassium excretion with adrenalectomy and increases in potassium excretion with aldosterone and in the potassium-adapted rat, consistent with described changes in potassium secretion. In contrast, with dexamethasone treatment, whilst there was an increase in UkV and UkV/PIK+, there was no change in UK# either in the control of potassium-adapted rats. These results suggest that the kaliuretic effect of dexamethasone cannot be attributed to direct tubular effects of glucocorticoids but rather can be explained by its effect on distal tubule flow.
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33
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Spence CD, Campbell DP, Coghlan JP, Denton DA, Mills EH, Nelson MA, Whitworth JA, Scoggins BA. Structure-activity relationships for blood pressure effects of prednisolone in sheep. CLINICAL AND EXPERIMENTAL HYPERTENSION. PART A, THEORY AND PRACTICE 1987; 9:773-95. [PMID: 3621626 DOI: 10.3109/10641968709161449] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
This study investigated the effect of 5 day infusions of 6 alpha and 9 alpha-fluoro and 16 alpha, 17 alpha-acetal analogues of prednisolone on blood pressure in conscious sheep. In vivo mineralocorticoid (MC) and glucocorticoid (GC) activities of these steroids were also measured. Prednisolone (100 mg/d) produced a small increase in mean arterial pressure associated with increased fasting plasma [glucose] and polyuria, but had no MC activity. 9 alpha-fluoro substitution greatly enhanced both the pressor and MC activity of prednisolone. The effect of 9 alpha-fluoro substitution on pressor activity was not affected by beta-methylation at C-16 (betamethasone), but was attenuated by either alpha-hydroxylation or alpha-methylation at C-16 (triamcinolone and dexamethasone, respectively). The effect of 9 alpha-fluoro substitution on MC activity as determined by urinary Na excretion was not altered by a methyl group at C-16 in either alpha or beta configuration but the MC activity was attenuated by an alpha-hydroxyl group at C-16. In contrast, 6 alpha-fluoro substitution had little influence on pressor, MC and GC activities. 16 alpha, 17 alpha-acetonide and 16 alpha, 17 alpha-butylidenedioxy substitution increased the pressor activity of parent compounds, but had no influence on either GC or MC activity. This study demonstrates a dissociation between the pressor effects and the MC and GC activities associated with steroid administration and provides further evidence to support the concept of 'hypertensinogenic' class of steroid activity which can be distinguished from their MC and GC activity.
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Bonvalet JP. Binding and action of aldosterone, dexamethasone, 1-25(OH)2D3, and estradiol along the nephron. JOURNAL OF STEROID BIOCHEMISTRY 1987; 27:953-61. [PMID: 3320569 DOI: 10.1016/0022-4731(87)90173-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The localization of specific binding sites of four steroids--aldosterone, dexamethasone, 1-25-dihydroxycholecalciferol and estradiol--is described along the nephron. This localization has been determined by using an autoradiographic method on dry films, applied to intact microdissected tubular segments. Aldosterone binds specifically to nuclei of the distal and cortical collecting tubule. No specific labeling was observed in the cytoplasm. This localization corresponds to the known sites of action of aldosterone on sodium reabsorption. Specific nuclear binding of dexamethasone is present all along the tubule except the proximal tubule. In this latter part of the nephron, a specific cytoplasmic labeling is observed, in the absence of nuclear labeling. This cytoplasmic binding could correspond to physiological effects in this structure, via non-genomic mechanisms. 1-25(OH)2D3 nuclear binding is located mainly in the loop of Henle and medullary collecting tubule, which are the sites of synthesis of calcium-binding proteins. No specific binding of estradiol is present in any part of the nephron.
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Affiliation(s)
- J P Bonvalet
- INSERM U246, Dépt. Biologie, CEN-Saclay, Gif-sur-Yvette, France
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35
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Beauwens R, Beaujean V, Zizi M, Rentmeesters M, Crabbé J. Increased chloride permeability of amphibian epithelia treated with aldosterone. Pflugers Arch 1986; 407:620-4. [PMID: 2432471 DOI: 10.1007/bf00582642] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The transepithelial flux of chloride was increased by aldosterone treatment of amphibian skin and bladder and this was reflected by increased "shunt" conductance. The hormonal effect depended on the presence of chloride on the epithelial side of the preparation. These changes in tissue conductance and chloride permeability appear to be a direct effect of aldosterone as they did not occur when sodium transport was stimulated with vasopressin or hypotonicity. Chloride efflux was reduced in magnitude by indacrinone and DIDS, as well as after removal of chloride from the solution on the epithelial side of the preparations. These results suggest that, rather than merely diffusing along (a) paracellular pathway(s), chloride flows through (a) cellular structure(s), notably mitochondria-rich cells. These cells can therefore be considered as targets for aldosterone.
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Perrone RD, Bengele HH, Alexander EA. Sodium retention after adrenal enucleation. THE AMERICAN JOURNAL OF PHYSIOLOGY 1986; 250:E1-12. [PMID: 3002187 DOI: 10.1152/ajpendo.1986.250.1.e1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Adrenal enucleation (removal of the adrenal gland, leaving the capsule intact) results in regeneration of the adrenal cortex. During the first 1-2 wk of adrenal regeneration, marked renal sodium avidity and positive sodium balance are noted. This renal sodium avidity appears mediated via adrenocorticotropin-stimulated secretion of a potent mineralocorticoid by the regenerating adrenal cortex. In this review, we have examined relationships between the histology and ultrastructure of the regenerating adrenal cortex, renal sodium handling, and adrenal steroid production at various times after the initiation of adrenal regeneration. Plasma levels of known mineralocorticoids are subnormal during the period of most intense sodium avidity, while urinary excretion of a potent mineralocorticoid, 19-nordeoxycorticosterone, has been found to be increased in rats with regenerating adrenals during this period of most intense sodium avidity. This hormone, however, is not elevated in rats with regenerating adrenals after resolution of the period of sodium avidity. In this article, we review the experimental evidence regarding the potency of this mineralocorticoid and its likely role in the sodium retention after adrenal enucleation.
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Suzuki S, Takamura S, Yoshida J, Ozaki N. Effect of aldosterone antagonists on aldosterone-induced activation of Mg2+ -HCO3- -ATPase and carbonic anhydrase in rat intestinal mucosa. JOURNAL OF STEROID BIOCHEMISTRY 1985; 23:57-66. [PMID: 3160893 DOI: 10.1016/0022-4731(85)90260-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In previous studies, Mg2+ -dependent, HCO3- -activated ATPase in the brush border and carbonic anhydrase in the cytoplasm of rat duodenal and jejunal mucosa decreased after adrenalectomy. Both enzyme activities increased to near normal levels 4 h after i.p. injection of aldosterone (40 micrograms/kg). These results suggest the possibility that both enzymes in the small intestinal mucosa may be mediators of the action of aldosterone. In the present studies, therefore, the effects of actinomycin D (500 micrograms/kg, i.p.), spironolactone (50 mg/kg, s.c.) and potassium canrenoate (50 mg/kg, s.c.) on aldosterone-induced activation of both enzymes in the upper small intestinal mucosa from adrenalectomized rats were examined to clarify the mechanism of action of aldosterone in enzyme levels. Actinomycin D inhibited carbonic anhydrase activity in small intestinal mucosa from normal rats 4 h after i.p. injection but had no effect on ATPase activity, while two other drugs had no effect on either enzyme activity in normal rats up to 4 h later. Pretreatment with these 3 drugs 1 h before aldosterone administration (40 micrograms/kg, i.p.) to adrenalectomized rats blocked the aldosterone-induced activation of ATPase and carbonic anhydrase in the upper small intestine. On the other hand, adrenalectomy and administration of aldosterone and its antagonists, alone or in combination, had no effect on kidney enzyme activities. These results confirm that Mg2+ -HCO3- -ATPase and carbonic anhydrase are mediators of the action of aldosterone in the upper small intestinal mucosa.
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Stanton B, Giebisch G, Klein-Robbenhaar G, Wade J, DeFronzo RA. Effects of adrenalectomy and chronic adrenal corticosteroid replacement on potassium transport in rat kidney. J Clin Invest 1985; 75:1317-26. [PMID: 3921569 PMCID: PMC425461 DOI: 10.1172/jci111832] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Clearance experiments were carried out in pair-fed rats to examine the long-term effects of adrenalectomy and selective adrenal corticosteroid replacement in physiological amounts on renal potassium transport. To this end, clearance studies were conducted in rats that were sham operated, or adrenalectomized (ADX). ADX animals were given either vehicle, aldosterone (0.5 microgram/100 g body wt per day), dexamethasone (1.2 micrograms/100 g body wt per day), or aldosterone and dexamethasone, by osmotic minipump for 7-9 d whereupon clearance experiments were conducted. After chronic hormone treatment, during basal conditions when only Ringers solution was infused, all groups excreted similar amounts of potassium. However, in all ADX animals without mineralocorticoid replacement, the maintenance of urinary potassium excretion at control levels was associated with hyperkalemia, increased urine flow, and natriuresis; all are factors known to stimulate urinary potassium excretion. During acute potassium infusion, the increase in urinary potassium excretion was less in ADX rats than in controls. This functional deficiency in potassium excretion was partially corrected by dexamethasone and was uniformly associated with a significant increase in urine flow. Aldosterone replacement or aldosterone and dexamethasone given together chronically, sharply increased potassium excretion but did not restore excretion to control levels. Only acute aldosterone infusion (0.2 microgram/100 g body wt bolus plus 0.2 microgram/100 g body wt per hour), superimposed upon chronic aldosterone and dexamethasone treatment, fully restored potassium excretion to control levels. This aldosterone induced enhancement of potassium excretion, both chronic and acute, was not associated with hyperkalemia, and increased urine flow or natriuresis. Thus, physiological levels of both classes of adrenal corticosteroids stimulate renal potassium excretion albeit by different mechanisms. Mineralocorticoids stimulate tubular potassium excretion directly, whereas glucocorticoids augment excretion indirectly by increasing fluid and sodium delivery along the distal nephron.
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40
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Field MJ, Stanton BA, Giebisch GH. Differential acute effects of aldosterone, dexamethasone, and hyperkalemia on distal tubular potassium secretion in the rat kidney. J Clin Invest 1984; 74:1792-802. [PMID: 6501571 PMCID: PMC425359 DOI: 10.1172/jci111598] [Citation(s) in RCA: 116] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
To determine the specific effects on renal potassium transport of acute elevations in plasma aldosterone, dexamethasone, and potassium concentrations, we studied adrenalectomized rats prepared such that each factor could be varied independently. Clearance data alone could not be used to deduce the underlying tubular transport effects, however, since infusion of each of these agents was associated with a marked change in urinary flow rate, which may itself have influenced potassium excretion. We therefore used a technique of continuous microperfusion, in vivo, of single superficial distal tubules to evaluate potassium secretion at constant luminal flow rate during each experimental maneuver. Acute aldosterone infusion was associated with a 90% stimulation of potassium secretion by microperfused tubules. However, total kidney sodium excretion and urinary flow rate were markedly reduced, and these factors opposed the direct tubular action of aldosterone, resulting in no net change in the amount of potassium excreted into the final urine. Conversely, dexamethasone had no direct effect on potassium secretion by single microperfused tubules, but it caused a sharp increase in urinary flow and sodium excretion, and secondarily enhanced urinary potassium excretion by 50%. Hyperkalemia per se stimulated renal potassium excretion both via a direct tubular effect and by increasing urinary flow rate. We conclude that urinary potassium excretion after infusion of each of these agents represents the net result of direct tubular effects and secondary flow-mediated changes.
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