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Johnston JG, Welch AK, Cain BD, Sayeski PP, Gumz ML, Wingo CS. Aldosterone: Renal Action and Physiological Effects. Compr Physiol 2023; 13:4409-4491. [PMID: 36994769 DOI: 10.1002/cphy.c190043] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Aldosterone exerts profound effects on renal and cardiovascular physiology. In the kidney, aldosterone acts to preserve electrolyte and acid-base balance in response to changes in dietary sodium (Na+ ) or potassium (K+ ) intake. These physiological actions, principally through activation of mineralocorticoid receptors (MRs), have important effects particularly in patients with renal and cardiovascular disease as demonstrated by multiple clinical trials. Multiple factors, be they genetic, humoral, dietary, or otherwise, can play a role in influencing the rate of aldosterone synthesis and secretion from the adrenal cortex. Normally, aldosterone secretion and action respond to dietary Na+ intake. In the kidney, the distal nephron and collecting duct are the main targets of aldosterone and MR action, which stimulates Na+ absorption in part via the epithelial Na+ channel (ENaC), the principal channel responsible for the fine-tuning of Na+ balance. Our understanding of the regulatory factors that allow aldosterone, via multiple signaling pathways, to function properly clearly implicates this hormone as central to many pathophysiological effects that become dysfunctional in disease states. Numerous pathologies that affect blood pressure (BP), electrolyte balance, and overall cardiovascular health are due to abnormal secretion of aldosterone, mutations in MR, ENaC, or effectors and modulators of their action. Study of the mechanisms of these pathologies has allowed researchers and clinicians to create novel dietary and pharmacological targets to improve human health. This article covers the regulation of aldosterone synthesis and secretion, receptors, effector molecules, and signaling pathways that modulate its action in the kidney. We also consider the role of aldosterone in disease and the benefit of mineralocorticoid antagonists. © 2023 American Physiological Society. Compr Physiol 13:4409-4491, 2023.
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Affiliation(s)
- Jermaine G Johnston
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Amanda K Welch
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Brian D Cain
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA
| | - Peter P Sayeski
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
| | - Michelle L Gumz
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Charles S Wingo
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
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Stadt MM, Leete J, Devinyak S, Layton AT. A mathematical model of potassium homeostasis: Effect of feedforward and feedback controls. PLoS Comput Biol 2022; 18:e1010607. [PMID: 36538563 PMCID: PMC9812337 DOI: 10.1371/journal.pcbi.1010607] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 01/04/2023] [Accepted: 11/28/2022] [Indexed: 12/24/2022] Open
Abstract
Maintaining normal potassium (K+) concentrations in the extra- and intracellular fluid is critical for cell function. K+ homeostasis is achieved by ensuring proper distribution between extra- and intracellular fluid compartments and by matching K+ excretion with intake. The Na+-K+-ATPase pump facilitates K+ uptake into the skeletal muscle, where most K+ is stored. Na+-K+-ATPase activity is stimulated by insulin and aldosterone. The kidneys regulate long term K+ homeostasis by controlling the amount of K+ excreted through urine. Renal handling of K+ is mediated by a number of regulatory mechanisms, including an aldosterone-mediated feedback control, in which high extracellular K+ concentration stimulates aldosterone secretion, which enhances urine K+ excretion, and a gastrointestinal feedforward control mechanism, in which dietary K+ intake increases K+ excretion. Recently, a muscle-kidney cross talk signal has been hypothesized, where the K+ concentration in skeletal muscle cells directly affects urine K+ excretion without changes in extracellular K+ concentration. To understand how these mechanisms coordinate under different K+ challenges, we have developed a compartmental model of whole-body K+ regulation. The model represents the intra- and extracellular fluid compartments in a human (male) as well as a detailed kidney compartment. We included (i) the gastrointestinal feedforward control mechanism, (ii) the effect of insulin and (iii) aldosterone on Na+-K+-ATPase K+ uptake, and (iv) aldosterone stimulation of renal K+ secretion. We used this model to investigate the impact of regulatory mechanisms on K+ homeostasis. Model predictions showed how the regulatory mechanisms synthesize to ensure that the extra- and intracelluller fluid K+ concentrations remain in normal range in times of K+ loading and fasting. Additionally, we predict that without the hypothesized muscle-kidney cross talk signal, the model was unable to predict a return to normal extracellular K+ concentration after a period of high K+ loading or depletion.
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Affiliation(s)
- Melissa M. Stadt
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
- * E-mail:
| | - Jessica Leete
- Computational Biology and Bioinformatics Program, Duke University, Durham, North Carolina, United States of America
| | - Sophia Devinyak
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Anita T. Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
- Cheriton School of Computer Science, University of Waterloo, Waterloo, Ontario, Canada
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
- Department of Pharmacy, University of Waterloo, Waterloo, Ontario, Canada
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Johnston JG, Wingo CS. Potassium Homeostasis and WNK Kinases in the Regulation of the Sodium-Chloride Cotransporter: Hyperaldosteronism and Its Metabolic Consequences. KIDNEY360 2022; 3:1823-1828. [PMID: 36514400 PMCID: PMC9717643 DOI: 10.34067/kid.0005752022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 10/12/2022] [Indexed: 12/05/2022]
Affiliation(s)
- Jermaine G. Johnston
- Department of Medicine, University of Florida, Gainesville, Florida,Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida,Veterans Administration Medical Center, North Florida/South Georgia Veterans Health Administration, Gainesville, Florida
| | - Charles S. Wingo
- Department of Medicine, University of Florida, Gainesville, Florida,Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida,Veterans Administration Medical Center, North Florida/South Georgia Veterans Health Administration, Gainesville, Florida
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Wu A, Wolley MJ, Matthews A, Cowley D, Welling PA, Fenton RA, Stowasser M. In Primary Aldosteronism Acute Potassium Chloride Supplementation Suppresses Abundance and Phosphorylation of the Sodium-Chloride Cotransporter. KIDNEY360 2022; 3:1909-1923. [PMID: 36514401 PMCID: PMC9717638 DOI: 10.34067/kid.0003632022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 08/25/2022] [Indexed: 01/12/2023]
Abstract
Background Elevated abundance of sodium-chloride cotransporter (NCC) and phosphorylated NCC (pNCC) are potential markers of primary aldosteronism (PA), but these effects may be driven by hypokalemia. Methods We measured plasma potassium in patients with PA. If potassium was <4.0 mmol/L, patients were given sufficient oral potassium chloride (KCl) over 24 hours to achieve as close to 4.0 mmol/L as possible. Clinical chemistries were assessed, and urinary extracellular vesicles (uEVs) were examined to investigate effects on NCC. Results Among 21 patients with PA who received a median total dose of 6.0 g (2.4-16.8 g) of KCl, increases were observed in plasma potassium (from 3.4 to 4.0 mmol/L; P<0.001), aldosterone (from 305 to 558 pmol/L; P=0.01), and renin (from 1.2 to 2.5 mIU/L; P<0.001), whereas decreases were detected in uEV levels of NCC (median fold change(post/basal) [FC]=0.71 [0.09-1.99]; P=0.02), pT60-NCC (FC=0.84 [0.06-1.66]; P=0.05), and pT55/60-NCC (FC=0.67 [0.08-2.42]; P=0.02). By contrast, in 10 patients with PA who did not receive KCl, there were no apparent changes in plasma potassium, NCC abundance, and phosphorylation status, but increases were observed in plasma aldosterone (from 178 to 418 pmol/L; P=0.006) and renin (from 2.0 to 3.0 mU/L; P=0.009). Plasma potassium correlated inversely with uEV levels of NCC (R 2=0.11; P=0.01), pT60-NCC (R 2=0.11; P=0.01), and pT55/60-NCC (R 2=0.11; P=0.01). Conclusions Acute oral KCl loading replenished plasma potassium in patients with PA and suppressed NCC abundance and phosphorylation, despite a significant rise in plasma aldosterone. This supports the view that potassium supplementation in humans with PA overrides the aldosterone stimulatory effect on NCC. The increased plasma aldosterone in patients with PA without KCl supplementation may be due to aldosterone response to posture challenge.
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Affiliation(s)
- Aihua Wu
- Endocrine Hypertension Research Centre, The University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
| | - Martin J. Wolley
- Endocrine Hypertension Research Centre, The University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia,Department of Nephrology, Royal Brisbane and Women’s Hospital, Brisbane, Australia
| | - Alexandra Matthews
- Endocrine Hypertension Research Centre, The University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
| | - Diane Cowley
- Endocrine Hypertension Research Centre, The University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
| | - Paul A. Welling
- Department of Medicine and Physiology, Johns Hopkins University, Baltimore, Maryland
| | | | - Michael Stowasser
- Endocrine Hypertension Research Centre, The University of Queensland Diamantina Institute, Greenslopes and Princess Alexandra Hospitals, Brisbane, Australia
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Wei KY, Gritter M, Vogt L, de Borst MH, Rotmans JI, Hoorn EJ. Dietary potassium and the kidney: lifesaving physiology. Clin Kidney J 2020; 13:952-968. [PMID: 33391739 PMCID: PMC7769543 DOI: 10.1093/ckj/sfaa157] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Indexed: 02/07/2023] Open
Abstract
Potassium often has a negative connotation in Nephrology as patients with chronic kidney disease (CKD) are prone to develop hyperkalaemia. Approaches to the management of chronic hyperkalaemia include a low potassium diet or potassium binders. Yet, emerging data indicate that dietary potassium may be beneficial for patients with CKD. Epidemiological studies have shown that a higher urinary potassium excretion (as proxy for higher dietary potassium intake) is associated with lower blood pressure (BP) and lower cardiovascular risk, as well as better kidney outcomes. Considering that the composition of our current diet is characterized by a high sodium and low potassium content, increasing dietary potassium may be equally important as reducing sodium. Recent studies have revealed that dietary potassium modulates the activity of the thiazide-sensitive sodium-chloride cotransporter in the distal convoluted tubule (DCT). The DCT acts as a potassium sensor to control the delivery of sodium to the collecting duct, the potassium-secreting portion of the kidney. Physiologically, this allows immediate kaliuresis after a potassium load, and conservation of potassium during potassium deficiency. Clinically, it provides a novel explanation for the inverse relationship between dietary potassium and BP. Moreover, increasing dietary potassium intake can exert BP-independent effects on the kidney by relieving the deleterious effects of a low potassium diet (inflammation, oxidative stress and fibrosis). The aim of this comprehensive review is to link physiology with clinical medicine by proposing that the same mechanisms that allow us to excrete an acute potassium load also protect us from hypertension, cardiovascular disease and CKD.
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Affiliation(s)
- Kuang-Yu Wei
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.,Department of Internal Medicine, Division of Nephrology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Martin Gritter
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Liffert Vogt
- Department of Internal Medicine, Division of Nephrology, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Martin H de Borst
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Joris I Rotmans
- Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, The Netherlands
| | - Ewout J Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Hoorn EJ, Gritter M, Cuevas CA, Fenton RA. Regulation of the Renal NaCl Cotransporter and Its Role in Potassium Homeostasis. Physiol Rev 2020; 100:321-356. [DOI: 10.1152/physrev.00044.2018] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Daily dietary potassium (K+) intake may be as large as the extracellular K+ pool. To avoid acute hyperkalemia, rapid removal of K+ from the extracellular space is essential. This is achieved by translocating K+ into cells and increasing urinary K+ excretion. Emerging data now indicate that the renal thiazide-sensitive NaCl cotransporter (NCC) is critically involved in this homeostatic kaliuretic response. This suggests that the early distal convoluted tubule (DCT) is a K+ sensor that can modify sodium (Na+) delivery to downstream segments to promote or limit K+ secretion. K+ sensing is mediated by the basolateral K+ channels Kir4.1/5.1, a capacity that the DCT likely shares with other nephron segments. Thus, next to K+-induced aldosterone secretion, K+ sensing by renal epithelial cells represents a second feedback mechanism to control K+ balance. NCC’s role in K+ homeostasis has both physiological and pathophysiological implications. During hypovolemia, NCC activation by the renin-angiotensin system stimulates Na+ reabsorption while preventing K+ secretion. Conversely, NCC inactivation by high dietary K+ intake maximizes kaliuresis and limits Na+ retention, despite high aldosterone levels. NCC activation by a low-K+ diet contributes to salt-sensitive hypertension. K+-induced natriuresis through NCC offers a novel explanation for the antihypertensive effects of a high-K+ diet. A possible role for K+ in chronic kidney disease is also emerging, as epidemiological data reveal associations between higher urinary K+ excretion and improved renal outcomes. This comprehensive review will embed these novel insights on NCC regulation into existing concepts of K+ homeostasis in health and disease.
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Affiliation(s)
- Ewout J. Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Martin Gritter
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Catherina A. Cuevas
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Robert A. Fenton
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
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Epstein M, Lifschitz MD. The Unappreciated Role of Extrarenal and Gut Sensors in Modulating Renal Potassium Handling: Implications for Diagnosis of Dyskalemias and Interpreting Clinical Trials. Kidney Int Rep 2016; 1:43-56. [PMID: 29142913 PMCID: PMC5678840 DOI: 10.1016/j.ekir.2016.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 03/11/2016] [Indexed: 12/11/2022] Open
Abstract
In addition to the classic and well-established "feedback control" of potassium balance, increasing investigative attention has focused on a novel and not widely recognized complementary regulatory paradigm for maintaining potassium homeostasis-the "feed-forward control" of potassium balance. This regulatory mechanism, initially defined in rumen, has recently been validated in normal human subjects. Studies are being conducted to determine the location for this putative potassium sensor and to evaluate potential signals, which might increase renal potassium excretion. Awareness of this more updated integrative control mechanism for potassium homeostasis is ever more relevant today, when the medical community is increasingly focused on the challenges of managing the hyperkalemia provoked by renin-angiotensin-aldosterone system inhibitors (RAASis). Recent studies have demonstrated a wide gap between RAASi prescribing guidelines and real-world experience and have highlighted that this gap is thought to be attributable in great part to hyperkalemia. Consequently we require a greater knowledge of the complexities of the regulatory mechanisms subserving potassium homeostasis. Sodium polystyrene sulfonate has long been the mainstay for treating hyperkalemia, but its administration is fraught with challenges related to patient discomfort and colonic necrosis. The current and imminent availability of newer potassium binders with better tolerability and more predictive dose-response potassium removal should enhance the management of hyperkalemia. Consequently it is essential to better understand the intricacies of mammalian colonic K+ handling. We discuss colonic transport of K+ and review evidence for potassium (BK) channels being responsible for increased stool K+ in patients with diseases such as ulcerative colitis.
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Affiliation(s)
- Murray Epstein
- Division of Nephrology and Hypertension, University of Miami, Miller School of Medicine, South Florida Veterans Affairs Foundation for Research and Education (SFVAFRE), Miami, Florida, USA
| | - Meyer D. Lifschitz
- Adult Nephrology Unit, Shaare Zedek Medical Center, Jerusalem, Israel
- University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
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Epstein M, Lifschitz MD. Potassium homeostasis and dyskalemias: the respective roles of renal, extrarenal, and gut sensors in potassium handling. Kidney Int Suppl (2011) 2016; 6:7-15. [PMID: 30675414 PMCID: PMC6340905 DOI: 10.1016/j.kisu.2016.01.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 01/08/2016] [Accepted: 01/08/2016] [Indexed: 12/11/2022] Open
Abstract
Integrated mechanisms controlling the maintenance of potassium homeostasis are well established and are defined by the classic "feedback control" of potassium balance. Recently, increasing investigative attention has focused on novel physiological paradigms that increase the complexity and precision of homeostasis. This review briefly considers the classic and well-established feedback control of potassium and then considers subsequent investigations that inform on an intriguing and not widely recognized complementary paradigm: the "feed-forward control of potassium balance." Feed-forward control refers to a pathway in a homeostatic system that responds to a signal in the environment in a predetermined manner, without responding to how the system subsequently reacts (i.e., without responding to feedback). Studies in several animal species, and recently in humans, have confirmed the presence of a feed-forward control mechanism that is capable of mediating potassium excretion independent of changes in serum potassium concentration and aldosterone. Knowledge imparted by this update of potassium homeostasis hopefully will facilitate the clinical management of hyperkalemia in patients with chronic and recurrent hyperkalemia. Awareness of this updated integrative control mechanism for potassium homeostasis is more relevant today when the medical community is increasingly focused on leveraging and expanding established renin-angiotensin-aldosterone system inhibitor treatment regimens and on successfully coping with the challenges of managing hyperkalemia provoked by renin-angiotensin-aldosterone system inhibitors. These new insights are relevant to the future design of clinical trials delineating renal potassium handling.
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Affiliation(s)
- Murray Epstein
- Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Meyer D. Lifschitz
- Adult Nephrology Unit, Shaare Zedek Medical Center, Jerusalem, Israel
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
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Evidence for a gastrointestinal–renal kaliuretic signaling axis in humans. Kidney Int 2015; 88:1383-1391. [DOI: 10.1038/ki.2015.243] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 06/18/2015] [Accepted: 06/18/2015] [Indexed: 01/20/2023]
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10
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Pachaly MA, Baena CP, Buiar AC, de Fraga FS, Carvalho M. Effects of non-pharmacological interventions on urinary citrate levels: a systematic review and meta-analysis. Nephrol Dial Transplant 2015; 31:1203-11. [DOI: 10.1093/ndt/gfv303] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 07/16/2015] [Indexed: 11/12/2022] Open
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Abstract
Extracellular K(+) homeostasis has been explained by feedback mechanisms in which changes in extracellular K(+) concentration drive renal K(+) excretion directly or indirectly via stimulating aldosterone secretion. However, this cannot explain meal-induced kaliuresis, which often occurs without increases in plasma K(+) or aldosterone concentrations. Recent studies have produced evidence supporting a feedforward control in which gut sensing of dietary K(+) increases renal K(+) excretion (and extrarenal K(+) uptake) independent of plasma K(+) concentrations, namely, a gut factor. This review focuses on these new findings and discusses the role of gut factor in acute and chronic regulation of extracellular K(+) as well as in the beneficial effects of high K(+) intake on the cardiovascular system.
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Affiliation(s)
- Jang H Youn
- Department of Physiology and Biophysics, University of Southern California Keck School of Medicine, Los Angeles, CA 90089-9142, USA.
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Rengarajan S, Lee DH, Oh YT, Delpire E, Youn JH, McDonough AA. Increasing plasma [K+] by intravenous potassium infusion reduces NCC phosphorylation and drives kaliuresis and natriuresis. Am J Physiol Renal Physiol 2014; 306:F1059-68. [PMID: 24598799 DOI: 10.1152/ajprenal.00015.2014] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Dietary potassium loading results in rapid kaliuresis, natriuresis, and diuresis associated with reduced phosphorylation (p) of the distal tubule Na(+)-Cl(-) cotransporter (NCC). Decreased NCC-p inhibits NCC-mediated Na(+) reabsorption and shifts Na(+) downstream for reabsorption by epithelial Na(+) channels (ENaC), which can drive K(+) secretion. Whether the signal is initiated by ingesting potassium or a rise in plasma K(+) concentration ([K(+)]) is not understood. We tested the hypothesis, in male rats, that an increase in plasma [K(+)] is sufficient to reduce NCC-p and drive kaliuresis. After an overnight fast, a single 3-h 2% potassium (2%K) containing meal increased plasma [K(+)] from 4.0 ± 0.1 to 5.2 ± 0.2 mM; increased urinary K(+), Na(+), and volume excretion; decreased NCC-p by 60%; and marginally reduced cortical Na(+)-K(+)-2Cl(-) cotransporter (NKCC) phosphorylation 25% (P = 0.055). When plasma [K(+)] was increased by tail vein infusion of KCl to 5.5 ± 0.1 mM over 3 h, significant kaliuresis and natriuresis ensued, NCC-p decreased by 60%, and STE20/SPS1-related proline alanine-rich kinase (SPAK) phosphorylation was marginally reduced 35% (P = 0.052). The following were unchanged at 3 h by either the potassium-rich meal or KCl infusion: Na(+)/H(+) exchanger 3 (NHE3), NHE3-p, NKCC, ENaC subunits, and renal outer medullary K(+) channel. In summary, raising plasma [K(+)] by intravenous infusion to a level equivalent to that observed after a single potassium-rich meal triggers renal kaliuretic and natriuretic responses, independent of K(+) ingestion, likely driven by decreased NCC-p and activity sufficient to shift sodium reabsorption downstream to where Na(+) reabsorption and flow drive K(+) secretion.
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Affiliation(s)
- Srinivas Rengarajan
- Cell and Neurobiology, Keck School of Medicine of USC, 1333 San Pablo St Los Angeles, CA 90033.
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Sorensen MV, Grossmann S, Roesinger M, Gresko N, Todkar AP, Barmettler G, Ziegler U, Odermatt A, Loffing-Cueni D, Loffing J. Rapid dephosphorylation of the renal sodium chloride cotransporter in response to oral potassium intake in mice. Kidney Int 2013; 83:811-24. [DOI: 10.1038/ki.2013.14] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Oh YT, Kim J, Youn JH. Role of pituitary in K+ homeostasis: impaired renal responses to altered K+ intake in hypophysectomized rats. Am J Physiol Regul Integr Comp Physiol 2013; 304:R1166-74. [PMID: 23594607 DOI: 10.1152/ajpregu.00495.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The kidneys maintain extracellular K⁺ homeostasis by altering K⁺ excretion to match K⁺ intake. Because this can occur without changes in plasma K⁺ concentrations ([K⁺]), how the kidneys sense K⁺ intake is unclear. We tested the hypothesis that the pituitary plays a critical role in signaling K⁺ intake to the kidneys. If this hypothesis is true, hypophysectomy would impair kidney responses to altered K⁺ intake. Hypophysectomized (Hypox) and sham-operated control rats (n = 8 each) were compared for their abilities to adjust K⁺ excretion during a transition from normal to reduced (to one-third of normal) K⁺ intake, followed by a reversal to normal K⁺ intake. Food was provided only at night, and renal K⁺ excretion was determined both for absorptive (night or feeding) and postabsorptive (day or nonfeeding) periods. In normal rats, both absorptive and postabsorptive renal K⁺ excretion were changed in parallel to the changes in K⁺ intake, indicating a rapid adaptation of normal kidneys to altered K⁺ intake. In Hypox rats, whereas absorptive renal K⁺ excretion was changed in response to changes in K⁺ intake, postabsorptive K⁺ excretion was not responsive (P < 0.001), indicating impaired renal responses to altered K⁺ intake. In addition, Hypox rats, compared with control rats, showed K⁺ intolerance (increases in plasma [K⁺]) upon feeding (i.e., K⁺ intake) at night or following an intravenous K⁺ infusion (P < 0.01), indicating an impairment of acute renal responses to K⁺ intake. These data support that the pituitary plays a key role in the signaling of K⁺ intake to the kidneys (and kidney responses to altered K⁺ intake).
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Affiliation(s)
- Young Taek Oh
- Department of Physiology and Biophysics, University of Southern California, Keck School of Medicine, Los Angeles, CA 90089, USA
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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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Oh KS, Oh YT, Kim SW, Kita T, Kang I, Youn JH. Gut sensing of dietary K⁺ intake increases renal K⁺excretion. Am J Physiol Regul Integr Comp Physiol 2011; 301:R421-9. [PMID: 21543632 DOI: 10.1152/ajpregu.00095.2011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Dietary K(+) intake may increase renal K(+) excretion via increasing plasma [K(+)] and/or activating a mechanism independent of plasma [K(+)]. We evaluated these mechanisms during normal dietary K(+) intake. After an overnight fast, [K(+)] and renal K(+) excretion were measured in rats fed either 0% K(+) or the normal 1% K(+) diet. In a third group, rats were fed with the 0% K(+) diet, and KCl was infused to match plasma [K(+)] profile to that of the 1% K(+) diet group. The 1% K(+) feeding significantly increased renal K(+) excretion, associated with slight increases in plasma [K(+)], whereas the 0% K(+) diet decreased K(+) excretion, associated with decreases in plasma [K(+)]. In the KCl-infused 0% K(+) diet group, renal K(+) excretion was significantly less than that of the 1% K(+) group, despite matched plasma [K(+)] profiles. We also examined whether dietary K(+) alters plasma profiles of gut peptides, such as guanylin, uroguanylin, glucagon-like peptide 1, and glucose-dependent insulinotropic polypeptide, pituitary peptides, such as AVP, α-MSH, and γ-MSH, or aldosterone. Our data do not support a role for these hormones in the stimulation of renal K(+) excretion during normal K(+) intake. In conclusion, postprandial increases in renal K(+) excretion cannot be fully accounted for by changes in plasma [K(+)] and that gut sensing of dietary K(+) is an important component of the regulation of renal K(+) excretion. Our studies on gut and pituitary peptide hormones suggest that there may be previously unknown humoral factors that stimulate renal K(+) excretion during dietary K(+) intake.
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Affiliation(s)
- Ki-Sook Oh
- Department of Physiology and Biophysics, University of Southern California, Keck School of Medicine, Los Angeles, California 90089-9142, USA
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Youn JH, McDonough AA. Recent advances in understanding integrative control of potassium homeostasis. Annu Rev Physiol 2009; 71:381-401. [PMID: 18759636 DOI: 10.1146/annurev.physiol.010908.163241] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The potassium homeostatic system is very tightly regulated. Recent studies have shed light on the sensing and molecular mechanisms responsible for this tight control. In addition to classic feedback regulation mediated by a rise in extracellular fluid (ECF) [K(+)], there is evidence for a feedforward mechanism: Dietary K(+) intake is sensed in the gut, and an unidentified gut factor is activated to stimulate renal K(+) excretion. This pathway may explain renal and extrarenal responses to altered K(+) intake that occur independently of changes in ECF [K(+)]. Mechanisms for conserving ECF K(+) during fasting or K(+) deprivation have been described: Kidney NADPH oxidase activation initiates a cascade that provokes the retraction of K(+) channels from the cell membrane, and muscle becomes resistant to insulin stimulation of cellular K(+) uptake. How these mechanisms are triggered by K(+) deprivation remains unclear. Cellular AMP kinase-dependent protein kinase activity provokes the acute transfer of K(+) from the ECF to the ICF, which may be important in exercise or ischemia. These recent advances may shed light on the beneficial effects of a high-K(+) diet for the cardiovascular system.
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Affiliation(s)
- Jang H Youn
- Department of Physiology and Biophysics, University of Southern California Keck School of Medicine, Los Angeles, California 90089-9142, 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
We tested the hypothesis that K+ intake is sensed by putative K+ sensors in the splanchnic areas, and renal K+ handling is regulated by this signal. K+ was infused for 2 h into overnight-fasted rats via the jugular vein (systemic infusion), hepatic portal vein (intraportal infusion), or stomach (intragastric infusion) ( n = 5 each), and plasma K+ concentration ([K+]) and renal K+ excretion were measured during the 2-h preinfusion, 2-h K+ infusion, and 3-h washout periods. During systemic K+ infusion, plasma [K+] increased by ∼1.3 mM ( P < 0.05), and, on cessation of the K+ infusion, plasma [K+] fell to the preinfusion level within 1–2 h. Renal K+ excretion changed in proportion to the changes in plasma [K+]. During intraportal or intragastric K+ infusion, plasma [K+] and renal K+ excretion profiles were similar to those with systemic infusion. The effects of K+ infusions via the different routes ( n = 5 or 6 each) were also studied during simultaneous feeding of overnight-fasted rats with a K+-deficient diet. During the meal, intraportal infusion resulted in increases in plasma [K+] similar to those with the systemic K+ infusion, while intragastric K+ infusion did not significantly increase plasma [K+]. Thus, when the intragastric K+ infusion was combined with a meal, there was marked enhancement of clearance of the K+ infused, which was associated with an apparent increase in renal efficiency of K+ excretion. These data suggest that there may be a gut factor that enhances renal efficiency of K+ excretion during meal (or dietary K+) intake.
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Affiliation(s)
- Felix N Lee
- Dept. of Physiology and Biophysics, Keck School of Medicine, University of Southern California, 1333 San Pablo St., MMR 626, Los Angeles, CA 90089-9142, USA
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Trindade AAT, Macedo CS, Riyuzo MC, Padovani CR, Bastos HD. Estudo da excreção urinária de cálcio, potássio e sódio com o emprego de citrato de potássio na hipercalciúria idiopática na criança. REVISTA PAULISTA DE PEDIATRIA 2007. [DOI: 10.1590/s0103-05822007000200004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJETIVO: Estudar as relações entre a excreção urinária de cálcio, sódio e potássio e a associação sódio/potássio urinários em crianças com hipercalciúria idiopática em dieta habitual, antes e depois da administração de citrato de potássio na dose de 1mEq/kg/dia. MÉTODOS: Foram estudadas prospectivamente 26 crianças: 19 (73%) meninos e sete (27%) meninas com idade entre dois e 13 anos, portadores de hipercalciúria idiopática recém-diagnosticada por dosagem de cálcio em urina de 24 horas >4mg/kg/dia. O citrato de potássio foi administrado na dose de 1mEq/kg/dia. Foram realizadas dosagens séricas e em urina de 24 horas de cálcio (Ca), potássio(K), sódio (Na) e creatinina (Cr), antes e 15 dias depois da administração diária do citrato de potássio. Para comparar os resultados de cálcio/creatinina (Ca/Cr), potássio/creatinina (K/Cr) e sódio/potássio (Na/K) urinários nos dois momentos, aplicou-se o teste não-paramétrico de Wilcoxon. Para a análise das associações entre Ca/Cr e K/Cr e entre Ca/Cr e Na/Cr foi utilizado o coeficiente de correlação de Pearson. Considerou-se significante p<0,05. RESULTADOS: Após o uso de citrato de potássio, ocorreu significativa redução da calciúria e da relação Na/K urinários, bem como elevação na caliúria. Não houve modificação da excreção urinária de sódio. CONCLUSÕES: Em dieta habitual, o citrato de potássio eleva a caliúria e diminui a calciúria em criança hipercalciúricas, sendo um eficaz recurso terapêutico.
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Morita H, Fujiki N, Miyahara T, Lee K, Tanaka K. Hepatoportal bumetanide-sensitive K(+)-sensor mechanism controls urinary K(+) excretion. Am J Physiol Regul Integr Comp Physiol 2000; 278:R1134-9. [PMID: 10801279 DOI: 10.1152/ajpregu.2000.278.5.r1134] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To determine whether a K(+)-sensor mechanism exists in the hepatoportal region, periarterial hepatic afferent nerve activity responses to intraportal injection of KCl were examined in anesthetized rats. Hepatic afferent nerve activity increased in response to intraportal injection in a K(+) concentration-dependent manner, and the increase was attenuated by inhibition of the Na(+)-K(+)-2Cl(-) cotransporter by bumetanide in a dose-dependent manner. These results suggest that a bumetanide-sensitive K(+)-sensor mechanism exists in the hepatoportal region. Stimulation of this mechanism by intraportal KCl infusion elicited an immediate and powerful kaliuresis with no significant change in the plasma K(+) concentration; this was significantly greater than the kaliuresis induced by intravenous KCl infusion and was attenuated by severing the periarterial hepatic nervous plexus. These results indicate that a hepatoportal bumetanide-sensitive K(+)-sensor mechanism senses the portal venous K(+) concentration and that stimulation of this sensor mechanism causes kaliuresis, which is mainly mediated by the periarterial hepatic nervous plexus.
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Affiliation(s)
- H Morita
- Department of Physiology, Gifu University School of Medicine, Gifu 500-8705, Japan.
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Lindinger MI, Franklin TW, Lands LC, Pedersen PK, Welsh DG, Heigenhauser GJ. NaHCO(3) and KHCO(3) ingestion rapidly increases renal electrolyte excretion in humans. J Appl Physiol (1985) 2000; 88:540-50. [PMID: 10658021 DOI: 10.1152/jappl.2000.88.2.540] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This paper describes and quantifies acute responses of the kidneys in correcting plasma volume, acid-base, and ion disturbances resulting from NaHCO(3) and KHCO(3) ingestion. Renal excretion of ions and water was studied in five men after ingestion of 3.57 mmol/kg body mass of sodium bicarbonate (NaHCO(3)) and, in a separate trial, potassium bicarbonate (KHCO(3)). Subjects had a Foley catheter inserted into the bladder and indwelling catheters placed into an antecubital vein and a brachial artery. Blood and urine were sampled in the 30-min period before, the 60-min period during, and the 210-min period after ingestion of the solutions. NaHCO(3) ingestion resulted in a rapid, transient diuresis and natriuresis. Cumulative urine output was 44 +/- 11% of ingested volume, resulting in a 555 +/- 119 ml increase in total body water at the end of the experiment. The cumulative increase (above basal levels) in renal Na(+) excretion accounted for 24 +/- 2% of ingested Na(+). In the KHCO(3) trial, arterial plasma K(+) concentration rapidly increased from 4.25 +/- 0.10 to a peak of 7.17 +/- 0.13 meq/l 140 min after the beginning of ingestion. This increase resulted in a pronounced, transient diuresis, with cumulative urine output at 270 min similar to the volume ingested, natriuresis, and a pronounced kaliuresis that was maintained until the end of the experiment. Cumulative (above basal) renal K(+) excretion at 270 min accounted for 26 +/- 5% of ingested K(+). The kidneys were important in mediating rapid corrections of substantial portions of the fluid and electrolyte disturbances resulting from ingestion of KHCO(3) and NaHCO(3) solutions.
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Affiliation(s)
- M I Lindinger
- Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph N1G 2W1, Canada L8N 3Z5.
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Osorio AV, Alon US. The relationship between urinary calcium, sodium, and potassium excretion and the role of potassium in treating idiopathic hypercalciuria. Pediatrics 1997; 100:675-81. [PMID: 9310524 DOI: 10.1542/peds.100.4.675] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
OBJECTIVES 1) To evaluate the relationships between urinary sodium (UNa), potassium (UK), and calcium (UCa) excretion in the pediatric population; and 2) to determine the effect of increasing potassium intake in patients with idiopathic hypercalciuria and investigate whether this intervention can be offered as another mode of therapy in this patient population. DESIGN Prospectively, we determined UNa, UK, UCa, and creatinine (Cr) concentrations in randomly collected urine samples from children on initial evaluation for urinary frequency, dysuria, hematuria, enuresis, or kidney stones to identify children with hypercalciuria. SETTING The outpatient renal clinic of an academic hospital. PARTICIPANTS Twenty-three black children (13 girls and 10 boys) and 77 white children (44 girls and 33 boys) 3.92 to 16.67 years of age. INTERVENTIONS Eleven children with hypercalciuria were given potassium supplementation or placed on a high-potassium diet for at least 2 weeks. OUTCOME MEASURES UNa to UK, UNa to Cr, UK to Cr, and UCa to Cr ratios were calculated from measured levels of urinary minerals. These were repeated in 11 hypercalciuric patients after 2 weeks of increased potassium intake. RESULTS A total of 100 urine samples were analyzed. The UCa/Cr ratio in blacks 0.04 +/- 0.06 (mean +/- standard deviation) was significantly lower than in whites 0.16 +/- 0.12. There were 21 hypercalciuric white children versus only 1 black child. Linear regression analysis revealed a positive direct correlation between UNa/Cr and UCa/Cr in all 100 subjects and in whites alone but not in blacks. An inverse relationship existed between UK/Cr and UCa/Cr in all subjects and in whites and showed a strong trend in blacks. A marked direct relationship was found between UNa/K and UCa/Cr in all subjects (r = .43) as well as in whites (r = .59) and blacks (r = .49). One black child and 10 white hypercalciuric children were treated with "extra" K for at least 2 weeks. The UNa/K decreased from 4.73 +/- 2.28 to 1.98 +/- 1.09, and the UCa/Cr decreased from 0. 31 +/- 0.10 to 0.14 +/- 0.07, with resolution or improvement of the patients' symptoms. CONCLUSIONS In our patient population with urinary symptoms, the UCa/Cr ratio in black children is lower and hypercalciuria less common than in white children. In both white and black populations, the UNa/K ratio had the strongest association with the UCa/Cr ratio, indicating an opposing role of UNa and UK on the UCa/Cr ratio. Increased potassium intake was found to be beneficial for hypercalciuric children by decreasing the UNa/K ratio and, consequently, the UCa/Cr ratio.
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Affiliation(s)
- A V Osorio
- Section of Pediatric Nephrology, Children's Mercy Hospital, University of Missouri at Kansas City, Missouri 64108, USA
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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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