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Leipziger J, Praetorius H. Renal Autocrine and Paracrine Signaling: A Story of Self-protection. Physiol Rev 2020; 100:1229-1289. [PMID: 31999508 DOI: 10.1152/physrev.00014.2019] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Autocrine and paracrine signaling in the kidney adds an extra level of diversity and complexity to renal physiology. The extensive scientific production on the topic precludes easy understanding of the fundamental purpose of the vast number of molecules and systems that influence the renal function. This systematic review provides the broader pen strokes for a collected image of renal paracrine signaling. First, we recapitulate the essence of each paracrine system one by one. Thereafter the single components are merged into an overarching physiological concept. The presented survey shows that despite the diversity in the web of paracrine factors, the collected effect on renal function may not be complicated after all. In essence, paracrine activation provides an intelligent system that perceives minor perturbations and reacts with a coordinated and integrated tissue response that relieves the work load from the renal epithelia and favors diuresis and natriuresis. We suggest that the overall function of paracrine signaling is reno-protection and argue that renal paracrine signaling and self-regulation are two sides of the same coin. Thus local paracrine signaling is an intrinsic function of the kidney, and the overall renal effect of changes in blood pressure, volume load, and systemic hormones will always be tinted by its paracrine status.
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Affiliation(s)
- Jens Leipziger
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; and Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Aarhus, Denmark
| | - Helle Praetorius
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; and Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Aarhus, Denmark
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Hu MC, Bobulescu IA, Quiñones H, Gisler SM, Moe OW. Dopamine reduces cell surface Na +/H + exchanger-3 protein by decreasing NHE3 exocytosis and cell membrane recycling. Am J Physiol Renal Physiol 2017; 313:F1018-F1025. [PMID: 28768665 DOI: 10.1152/ajprenal.00251.2017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 07/14/2017] [Accepted: 07/24/2017] [Indexed: 01/06/2023] Open
Abstract
The intrarenal autocrine-paracrine dopamine (DA) system mediates a significant fraction of the natriuresis in response to a salt load. DA inhibits a number of Na+ transporters to effect sodium excretion, including the proximal tubule Na+/H+ exchanger-3 (NHE3). DA represent a single hormone that regulates NHE3 at multiple levels, including translation, degradation, endocytosis, and protein phosphorylation. Because cell surface NHE3 protein is determined by the balance between exocytotic insertion and endocytotic retrieval, we examined whether DA acutely affects the rate of NHE3 exocytosis in a cell culture model. DA inhibited NHE3 exocytosis at a dose-dependent manner with a half maximal around 10-6 M. The DA effect on NHE3 exocytosis was blocked by inhibition of protein kinase A and by brefeldin A, which inhibits endoplasmic reticulum-to-Golgi transport. NHE3 directly interacts with the ε-subunit of coatomer protein based on yeast-two-hybrid and coimmunoprecipitation. Because NHE3 has been shown to be recycled back to the cell membrane after endocytosis, we measured NHE3 recycling using a biochemical reinsertion assay and showed that reinsertion of NHE3 back to the membrane is also inhibited by DA. In conclusion, among the many mechanisms by which DA reduces apical membrane NHE3 and induces proximal tubule natriuresis, one additional mechanism is inhibition of exocytotic insertion and reinsertion of NHE3 in the apical cell surface.
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Affiliation(s)
- Ming Chang Hu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; .,Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - I Alexandru Bobulescu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Henry Quiñones
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Serge M Gisler
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Orson W Moe
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas; and.,Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
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Lin Z, Zhao C, Luo Q, Xia X, Yu X, Huang F. Prevalence of restless legs syndrome in chronic kidney disease: a systematic review and meta-analysis of observational studies. Ren Fail 2016; 38:1335-1346. [PMID: 27765002 DOI: 10.1080/0886022x.2016.1227564] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
INTRODUCTION Nowadays prevalence of restless legs syndrome (RLS) in chronic kidney disease (CKD) patients was reported in many studies, while the results varied. The aim of our study was to investigate the prevalence of RLS in this population, considering different data collecting measures and diagnostic criteria. METHODS MEDLINE, Embase, PsycINFO, and Scopus databases were searched for relevant studies. We limited the analyses to studies using clinical interview or questionnaire for diagnosis. Univariate meta-regression analysis was preformed to assess the effects of the disease-related covariates on prevalence estimates. Comprehensive Meta-Analysis 2.0 was used to perform the meta-analysis. RESULTS Fifty-one studies were included in the analysis. Prevalence of RLS was varied by renal function and diagnostic methods. Overall prevalence in CKD populations was 24.2% (95%CI, 20.1-28.7). Pooled prevalence of RLS was higher in patients diagnosed by questionnaire than by clinical interview [26.2% (95%CI, 17.9-36.5) vs. 23.6% (95%CI, 19.6-28.1)]. When grouped by CKD setting, the prevalence was 28.4% (95%CI, 24.6-32.6) in dialysis patients, followed by early stages patients [9.9% (95%CI, 5.4-17.5)], and kidney transplant recipients [6.7% (95%CI, 5.6-7.8)]. CONCLUSIONS Our meta-analysis suggested that more than one-quarter of CKD sufferers, especially those who were on dialysis, were plagued by RLS. Higher sensitivity of diagnostic criteria in interview may be valuable for timely treatment.
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Affiliation(s)
- Zhenchuan Lin
- a Department of Nephrology , The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health , Guangzhou , China
| | - Chen Zhao
- a Department of Nephrology , The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health , Guangzhou , China
| | - Qimei Luo
- a Department of Nephrology , The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health , Guangzhou , China
| | - Xi Xia
- a Department of Nephrology , The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health , Guangzhou , China
| | - Xueqing Yu
- a Department of Nephrology , The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health , Guangzhou , China
| | - Fengxian Huang
- a Department of Nephrology , The First Affiliated Hospital, Sun Yat-sen University, Key Laboratory of Nephrology, Ministry of Health , Guangzhou , China
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Shaman AM, Kowalski SR. Hyperphosphatemia Management in Patients with Chronic Kidney Disease. Saudi Pharm J 2015; 24:494-505. [PMID: 27330380 PMCID: PMC4908098 DOI: 10.1016/j.jsps.2015.01.009] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 01/01/2015] [Indexed: 01/07/2023] Open
Abstract
Hyperphosphatemia in chronic kidney disease (CKD) patients is a potentially life altering condition that can lead to cardiovascular calcification, metabolic bone disease (renal osteodystrophy) and the development of secondary hyperparathyroidism (SHPT). It is also associated with increased prevalence of cardiovascular diseases and mortality rates. To effectively manage hyperphosphatemia in CKD patients it is important to not only consider pharmacological and nonpharmacological treatment options but also to understand the underlying physiologic pathways involved in phosphorus homoeostasis. This review will therefore provide both a background into phosphorus homoeostasis and the management of hyperphosphatemia in CKD patients. In addition, it will cover some of the most important reasons for failure to control hyperphosphatemia with emphasis on the effect of the gastric pH on phosphate binders efficiency.
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Affiliation(s)
- Ahmed M Shaman
- Department of Clinical Pharmacy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Stefan R Kowalski
- School of Pharmacy and Medical Sciences, University of South Australia, South Australia, Australia
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Abstract
Recent studies of inherited disorders of phosphate metabolism have shed new light on the understanding of phosphate metabolism. Phosphate has important functions in the body and several mechanisms have evolved to regulate phosphate balance including vitamin D, parathyroid hormone and phosphatonins such as fibroblast growth factor-23 (FGF23). Disorders of phosphate homeostasis leading to hypo- and hyperphosphataemia are common and have clinical and biochemical consequences. Notably, recent studies have linked hyperphosphataemia with an increased risk of cardiovascular disease. This review outlines the recent advances in the understanding of phosphate homeostasis and describes the causes, investigation and management of hypo- and hyperphosphataemia.
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Affiliation(s)
- P Manghat
- Department of Chemical Pathology, Darent Valley Hospital, Dartford, UK
| | - R Sodi
- Department of Biochemistry, NHS Lanarkshire, East Kilbride, UK
| | - R Swaminathan
- Department of Chemical Pathology, St. Thomas Hospital, London, UK
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Biber J, Murer H, Mohebbi N, Wagner C. Renal Handling of Phosphate and Sulfate. Compr Physiol 2014; 4:771-92. [DOI: 10.1002/cphy.c120031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Seidel S, Böck A, Schlegel W, Kilic A, Wagner G, Gelbmann G, Hübenthal A, Kanbur I, Natriashvili S, Karwautz A, Wöber C, Wöber-Bingöl C. Increased RLS prevalence in children and adolescents with migraine: a case-control study. Cephalalgia 2012; 32:693-9. [PMID: 22659118 DOI: 10.1177/0333102412446207] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Previous studies have reported an increased frequency of restless legs syndrome (RLS) in adult migraine patients. Until now, the frequency of RLS in pediatric patients has not been investigated. We set out to assess the frequency of RLS in children and adolescents with migraine compared to headache-free controls. METHODS We investigated 111 consecutive patients with a sole diagnosis of migraine with or without aura presenting to the Headache Unit at the Department of Child and Adolescent Psychiatry and 73 headache-free controls for the presence of RLS using a semistructured interview. In addition, we assessed the level of daytime sleepiness by means of the Epworth sleepiness scale (ESS). A second group of headache-free controls was screened for the presence of RLS using an online questionnaire. RESULTS The frequency of RLS in migraine patients was significantly higher than in controls (22% vs. 5% (p < 0.001) and 8% (p < 0.001)). DISCUSSION This is the first study suggesting an association between RLS and migraine in the pediatric population. Future studies are needed to determine the extent of sleep disruption in children and adolescents with migraine and comorbid RLS.
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Affiliation(s)
- Stefan Seidel
- Headache Unit at the Department of Neurology, Medical University of Vienna, Austria
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Suzuki S, Suzuki K, Miyamoto M, Miyamoto T, Watanabe Y, Takashima R, Hirata K. Evaluation of contributing factors to restless legs syndrome in migraine patients. J Neurol 2011; 258:2026-35. [PMID: 21538231 DOI: 10.1007/s00415-011-6064-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Revised: 04/14/2011] [Accepted: 04/19/2011] [Indexed: 10/18/2022]
Abstract
Recent studies have provided evidence for a positive association between migraine and restless legs syndrome (RLS), although the exact mechanisms and contributing factors remain unclear. A cross-sectional, case-control study was conducted, including patients with migraine (n = 262) and headache-free control subjects (n = 163). Migraine was diagnosed according to International Classification of Headache Disorders II criteria. RLS diagnosis was made based on four essential criteria as described by the International Restless Legs Syndrome Study Group. All patients completed the Migraine Disability Assessment (MIDAS) questionnaire, Beck Depression Inventory (BDI)-II scores, Pittsburgh Sleep Quality Index (PSQI), and Epworth Sleepiness Scale (ESS). A total of 210 blood samples were collected to correlate various parameters with RLS. RLS frequency was significantly greater in patients with migraine than in controls (13.7 vs. 1.8%). Migraine patients with RLS had high scores for MIDAS, BDI-II, PSQI, and ESS compared with those without RLS. In addition, migraine patients with RLS had a high rate of smoking and RLS family history, as well as increased levels of serum phosphorus and urea nitrogen compared with those without RLS. However, there was no difference in serum iron and ferritin levels between the groups. In migraine patients, logistic regression analysis revealed that positive RLS family history, BDI-II, ESS, and serum phosphorus levels were significant RLS predictors. Our study confirmed a positive association between RLS and migraine. RLS comorbidity in migraine patients was associated with insomnia, daytime sleepiness, depressive symptoms, headache-related disability, and increased serum phosphorus levels. These findings may provide a better understanding of RLS pathogenesis in migraine.
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Affiliation(s)
- Shiho Suzuki
- Department of Neurology, Dokkyo Medical University, 880 Kitakobayashi, Mibu, Tochigi 321-0293, Japan
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Zhang MZ, Yao B, Fang X, Wang S, Smith JP, Harris RC. Intrarenal dopaminergic system regulates renin expression. Hypertension 2009; 53:564-70. [PMID: 19139376 DOI: 10.1161/hypertensionaha.108.127035] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Dopamine is a major regulator of proximal tubule salt reabsorption and is a modulator of renin release. Dopamine has been reported to stimulate renin release in vitro through activation of D1-like receptors. However, previous studies investigating dopamine regulation of renin release in vivo have provided contradictory results, indicating stimulation, inhibition, or no effect. We have reported previously that macula densa cyclooxygenase-2 (COX-2) is suppressed by dopamine. Because macula densa COX-2 stimulates renal renin expression, our current studies investigated dopamine regulation of renal renin release and synthesis in vivo. Acute treatment with a D1-like receptor agonist, fenoldopam, significantly inhibited renin release, as did acute inhibition of proximal tubule salt reabsorption with acetazolamide. In catechol-O-methyl transferase knockout (COMT(-/-)) mice, which have increased kidney dopamine levels because of deletion of the major intrarenal dopamine metabolizing enzyme, there was attenuation in response to a low-salt diet of the increases of renal cortical COX-2 and renin expression and renin release. A high-salt diet led to significant decreases in renal renin expression but much less significant decreases in COMT(-/-) mice than wild type mice, resulting in higher renal renin expression in COMT(-/-) mice. In high salt-treated wild-type mice or COX-2 knockout mice on a normal salt diet, fenoldopam stimulated renal renin expression. These results suggest that dopamine predominantly inhibits renal renin expression and release by inhibiting macula densa COX-2, but suppression of renal cortical COX-2 activity reveals a contrasting effect of dopamine to stimulate renal renin expression through activation of D1-like receptors.
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Affiliation(s)
- Ming-Zhi Zhang
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
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Zeng C, Sanada H, Watanabe H, Eisner GM, Felder RA, Jose PA. Functional genomics of the dopaminergic system in hypertension. Physiol Genomics 2005; 19:233-46. [PMID: 15548830 DOI: 10.1152/physiolgenomics.00127.2004] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Abnormalities in dopamine production and receptor function have been described in human essential hypertension and rodent models of genetic hypertension. Under normal conditions, D(1)-like receptors (D(1) and D(5)) inhibit sodium transport in the kidney and intestine. However, in the Dahl salt-sensitive and spontaneously hypertensive rats (SHRs) and in humans with essential hypertension, the D(1)-like receptor-mediated inhibition of epithelial sodium transport is impaired because of an uncoupling of the D(1)-like receptor from its G protein/effector complex. The uncoupling is receptor specific, organ selective, nephron-segment specific, precedes the onset of hypertension, and cosegregates with the hypertensive phenotype. The defective transduction of the renal dopaminergic signal is caused by activating variants of G protein-coupled receptor kinase type 4 (GRK4: R65L, A142V, A486V). The GRK4 locus is linked to and GRK4 gene variants are associated with human essential hypertension, especially in salt-sensitive hypertensive subjects. Indeed, the presence of three or more GRK4 variants impairs the natriuretic response to dopaminergic stimulation in humans. In genetically hypertensive rats, renal inhibition of GRK4 expression ameliorates the hypertension. In mice, overexpression of GRK4 variants causes hypertension either with or without salt sensitivity according to the variant. GRK4 gene variants, by preventing the natriuretic function of the dopaminergic system and by allowing the antinatriuretic factors (e.g., angiotensin II type 1 receptor) to predominate, may be responsible for salt sensitivity. Subclasses of hypertension may occur because of additional perturbations caused by variants of other genes, the quantitative interaction of which may vary depending upon the genetic background.
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Affiliation(s)
- Chunyu Zeng
- Department of Cardiology, Daping Hospital, Third Military Medical University, Chongqing, People's Republic of China
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Takaki J, Nishi T, Nangaku M, Shimoyama H, Inada T, Matsuyama N, Kumano H, Kuboki T. Clinical and psychological aspects of restless legs syndrome in uremic patients on hemodialysis. Am J Kidney Dis 2003; 41:833-9. [PMID: 12666070 DOI: 10.1016/s0272-6386(03)00031-3] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
BACKGROUND The pathogenesis of restless legs syndrome (RLS) is still unclear. The purpose of this study is to determine relationships of the presence of RLS in uremic patients regularly undergoing hemodialysis (HD) with demographic, clinical, and psychological factors. METHODS In 490 uremic patients on HD therapy in Japan, RLS was diagnosed based on diagnostic criteria established by the International Restless Legs Syndrome Study Group. Data were compared between patients with and without RLS. RESULTS There were univariately significant (P < 0.05) differences in serum phosphorus levels, anxiety levels determined using the Hospital Anxiety and Depression Scale, and degrees of emotion-oriented and avoidance-oriented coping determined using the Coping Inventory for Stressful Situations. In multivariate analyses, low hemoglobin levels, high serum phosphorus levels, high anxiety levels, and a great degree of emotion-oriented coping were independently related to the presence of RLS in uremic patients on HD therapy, with statistical significance (P < 0.05). CONCLUSION Hyperphosphatemia, anxiety, and a great degree of emotion-oriented coping with stress were independently related to the presence of RLS in uremic patients on HD therapy. The pathogenesis of RLS seems to involve more than one mechanism, which leads to restless legs as the final common pathway. These findings may provide new clues to the pathogenesis of RLS.
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Affiliation(s)
- Jiro Takaki
- Department of Psychosomatic Medicine, Tokyo University Hospital, Faculty of Medicine, University of Tokyo, Tokyo Japan.
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Doggrell SA. The therapeutic potential of dopamine modulators on the cardiovascular and renal systems. Expert Opin Investig Drugs 2002; 11:631-44. [PMID: 11996645 DOI: 10.1517/13543784.11.5.631] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
In the periphery, physiological dopamine increases renal blood flow, decreases renal resistance and acts on the kidney tubule to enhance natriuresis and diuresis. The loss of dopamine function may be involoved in the deterioration in kidney function associated with ageing and may have a role in the pathogenesis of hypertension and diabetes. Intravenous dopamine is used as a positive inotrope in the treatment of acute heart failure and cardiogenic shock and as a diuretic in renal failure. The clinical uses of dopamine are limited, as it must be given intravenously, and also has widespread effects. The levels of peripheral dopamine can be increased by the administration of L-dopa to increase synthesis, prodrugs to release dopamine (docarpamine, glu-dopa) or by inhibiting the breakdown of dopamine (nitecapone). Preliminary clinical trials suggest that docarpamine may be useful in patients with low cardiac output syndrome after cardiac surgery and in refractory cirrhotic ascites. Ibopamine is an agonist at dopamine D1 and D2 receptors, which may retard the progression of chronic renal failure. Glu-dopa is selective for the kidney, thus avoiding widespread side effects. The early clinical studies with ibopamine as a diuretic in heart failure were favourable but the subsequent large mortality study showed that ibopamine increased mortality. Fenoldopam is a selective dopamine D1 receptor agonist. Intravenous fenoldopam may be useful in the treatment of hypertension associated with coronary artery bypass surgery or in hypertensive emergencies. Although our understanding of physiological and pathological roles of peripheral dopamine has been increasing rapidly in recent times, we still need more information to allow the design of clinically useful drugs that modify these roles. One priority is an orally-active selective dopamine D1 receptor agonist.
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Affiliation(s)
- Sheila A Doggrell
- Department of Physiology and Pharmacology, School of Biomedical Sciences, The University of Queensland, QLD 4072, Australia.
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Murer H, Hernando N, Forster I, Biber J. Proximal tubular phosphate reabsorption: molecular mechanisms. Physiol Rev 2000; 80:1373-409. [PMID: 11015617 DOI: 10.1152/physrev.2000.80.4.1373] [Citation(s) in RCA: 390] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Renal proximal tubular reabsorption of P(i) is a key element in overall P(i) homeostasis, and it involves a secondary active P(i) transport mechanism. Among the molecularly identified sodium-phosphate (Na/P(i)) cotransport systems a brush-border membrane type IIa Na-P(i) cotransporter is the key player in proximal tubular P(i) reabsorption. Physiological and pathophysiological alterations in renal P(i) reabsorption are related to altered brush-border membrane expression/content of the type IIa Na-P(i) cotransporter. Complex membrane retrieval/insertion mechanisms are involved in modulating transporter content in the brush-border membrane. In a tissue culture model (OK cells) expressing intrinsically the type IIa Na-P(i) cotransporter, the cellular cascades involved in "physiological/pathophysiological" control of P(i) reabsorption have been explored. As this cell model offers a "proximal tubular" environment, it is useful for characterization (in heterologous expression studies) of the cellular/molecular requirements for transport regulation. Finally, the oocyte expression system has permitted a thorough characterization of the transport characteristics and of structure/function relationships. Thus the cloning of the type IIa Na-P(i )cotransporter (in 1993) provided the tools to study renal brush-border membrane Na-P(i) cotransport function/regulation at the cellular/molecular level as well as at the organ level and led to an understanding of cellular mechanisms involved in control of proximal tubular P(i) handling and, thus, of overall P(i) homeostasis.
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Affiliation(s)
- H Murer
- Institute of Physiology, University of Zürich, Zürich, Switzerland.
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Abstract
The kidney regulates sodium metabolism with extraordinary precision and sensitivity. This is accomplished by an intricate interaction between signals from extrarenal and intrarenal sources and between anti-natriuretic and natriuretic factors. Dopamine, produced in renal proximal tubule cells, plays a central role in this interactive network. Natriuretic hormones that are released from extrarenal sources, such as atrial natriuretic peptide, mediate some of their effects via renal dopamine receptors. On the level of the tubules, dopamine acts by opposing the effects of anti-natriuretic factors, such as angiotensin II and alpha-adrenergic receptors. Sodium retention leads to an increase in renal dopamine tonus, and the natriuretic effects of dopamine are more prominent under this condition. Inhibition or down-regulation of dopamine receptors significantly attenuates the natriuretic response to salt loading. Renal dopamine is modulated by the supply of filtered L-DOPA and the metabolism of dopamine via catechol-O-methyldopamine. The importance of dopamine as a natriuretic hormone is reflected by its capacity to inhibit the majority of renal tubule sodium transporters. Notably, the activity of Na+, K+ ATPase is inhibited in most tubule segments by dopamine. Recent studies have elucidated many of the signaling pathways for renal dopamine receptors. Novel principles for homologous and heterologous sensitization of dopamine receptors have been detected that may explain some of the interaction between dopamine and other first messengers that modulate renal tubule sodium transport. A broad understanding of the renal dopamine system has become increasingly important, since there is now strong evidence from both clinical and experimental studies that dysregulation of the renal dopamine system plays a role in many forms of multigenetic hypertension.
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Affiliation(s)
- A C Aperia
- Karolinska Institutet, Department of Woman and Child Health, Stockholm, Sweden
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Brismar H, Holtbäck U, Aperia A. Mechanisms by which intrarenal dopamine and ANP interact to regulate sodium metabolism. Clin Exp Hypertens 2000; 22:303-7. [PMID: 10803735 DOI: 10.1081/ceh-100100079] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Maintenance of a normal blood pressure requires a precise and fine-tuned regulation of salt metabolism. This is accomplished by a bidirectional regulation of renal tubular sodium transporters by natriuretic and antinatriuretic hormones. Dopamine, produced in the renal proximal tubular cells, plays an important role in this interactive system. Dopamine inhibits the activity of Na+,K+ ATPase as well as of many important sodium influx pathways in the nephron. These effects of dopamine are particularly pronounced in situation of sodium loading. There is an abundance of evidence suggesting that the natriuretic effects of ANP are to a large extent mediated via renal dopamine 1 like receptors. The renal tubular dopamine 1 like receptors are, under basal conditions, mainly located intracellularly. ANP and its second messenger, cGMP, cause a rapid translocation of the dopamine 1 like receptors to the plasma membrane. This phenomenon may explain how ANP and dopamine act in concert to regulate sodium metabolism. Regulation of sodium metabolism and blood pressure is critically dependent on a normal function of the renal dopamine system. Hence, abnormalities in the interaction between dopamine and ANP may predispose to hypertension.
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Affiliation(s)
- H Brismar
- Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden
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