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Renal water transport in health and disease. Pflugers Arch 2022; 474:841-852. [PMID: 35678906 PMCID: PMC9338902 DOI: 10.1007/s00424-022-02712-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 05/11/2022] [Accepted: 05/19/2022] [Indexed: 12/12/2022]
Abstract
Saving body water by optimal reabsorption of water filtered by the kidney leading to excretion of urine with concentrations of solutes largely above that of plasma allowed vertebrate species to leave the aquatic environment to live on solid ground. Filtered water is reabsorbed for 70% and 20% by proximal tubules and thin descending limbs of Henle, respectively. These two nephron segments express the water channel aquaporin-1 located along both apical and basolateral membranes. In the proximal tubule, the paracellular pathway accounts for at least 30% of water reabsorption, and the tight-junction core protein claudin-2 plays a key role in this permeability. The ascending limb of Henle and the distal convoluted tubule are impermeant to water and are responsible for urine dilution. The water balance is adjusted along the collecting system, i.e. connecting tubule and the collecting duct, under the control of arginine-vasopressin (AVP). AVP is synthesized by the hypothalamus and released in response to an increase in extracellular osmolality or stimulation of baroreceptors by decreased blood pressure. In response to AVP, aquaporin-2 water channels stored in subapical intracellular vesicles are translocated to the apical plasma membrane and raise the water permeability of the collecting system. The basolateral step of water reabsorption is mediated by aquaporin-3 and -4, which are constitutively expressed. Drugs targeting water transport include classical diuretics, which primarily inhibit sodium transport; the new class of SGLT2 inhibitors, which promotes osmotic diuresis and the non-peptidic antagonists of the V2 receptor, which are pure aquaretic drugs. Disturbed water balance includes diabetes insipidus and hyponatremias. Diabetes insipidus is characterized by polyuria and polydipsia. It is either related to a deficit in AVP secretion called central diabetes insipidus that can be treated by AVP analogs or to a peripheral defect in AVP response called nephrogenic diabetes insipidus. Diabetes insipidus can be either of genetic origin or acquired. Hyponatremia is a common disorder most often related to free water excess relying on overstimulated or inappropriate AVP secretion. The assessment of blood volume is key for the diagnosis and treatment of hyponatremia, which can be classified as hypo-, eu-, or hypervolemic.
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Aikins AO, Nguyen DH, Paundralingga O, Farmer GE, Shimoura CG, Brock C, Cunningham JT. Cardiovascular Neuroendocrinology: Emerging Role for Neurohypophyseal Hormones in Pathophysiology. Endocrinology 2021; 162:6247962. [PMID: 33891015 PMCID: PMC8234498 DOI: 10.1210/endocr/bqab082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Indexed: 11/19/2022]
Abstract
Arginine vasopressin (AVP) and oxytocin (OXY) are released by magnocellular neurosecretory cells that project to the posterior pituitary. While AVP and OXY currently receive more attention for their contributions to affiliative behavior, this mini-review discusses their roles in cardiovascular function broadly defined to include indirect effects that influence cardiovascular function. The traditional view is that neither AVP nor OXY contributes to basal cardiovascular function, although some recent studies suggest that this position might be re-evaluated. More evidence indicates that adaptations and neuroplasticity of AVP and OXY neurons contribute to cardiovascular pathophysiology.
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Affiliation(s)
- Ato O Aikins
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - Dianna H Nguyen
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
- Texas College of Osteopathic Medicine, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - Obed Paundralingga
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - George E Farmer
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - Caroline Gusson Shimoura
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - Courtney Brock
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - J Thomas Cunningham
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
- Correspondence: J. Thomas Cunningham Department of Physiology & Anatomy CBH 338 UNT Health Science Center 3500 Camp Bowie Blvd Fort Worth, TX 76107, USA.
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Management of Cirrhotic Ascites under the Add-on Administration of Tolvaptan. Int J Mol Sci 2021; 22:ijms22115582. [PMID: 34070416 PMCID: PMC8197450 DOI: 10.3390/ijms22115582] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/21/2021] [Accepted: 05/22/2021] [Indexed: 12/15/2022] Open
Abstract
Tolvaptan is a recently available diuretic that blocks arginine vasopressin receptor 2 in the renal collecting duct. Its diuretic mechanism involves selective water reabsorption by affecting the water reabsorption receptor aquaporin 2. Given that liver cirrhosis patients exhibit hyponatremia due to their pseudo-aldosteronism and usage of natriuretic agents, a sodium maintaining agent, such as tolvaptan, is physiologically preferable. However, large scale studies indicating the patients for whom this would be effective and describing management under its use have been insufficient. The appropriate management of cirrhosis patients treated with tolvaptan should be investigated. In the present review, we collected articles investigating the effectiveness of tolvaptan and factors associated with survival and summarized their management reports. Earlier administration of tolvaptan before increasing the doses of natriuretic agents is recommended because this may preserve effective arterial blood volume.
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Adachi T, Takaki A, Sato S, Tobita H, Kobashi H, Kinomura M, Nakatsuka A, Oyama A, Wada N, Sakata M, Takeuchi Y, Yasunaka T, Onishi H, Shiraha H, Okada H. High expression of a vascular stricture-related marker is predictive of an early response to tolvaptan, and a low fractional excretion of sodium is predictive of a poor long-term survival after tolvaptan administration for liver cirrhosis. Hepatol Res 2020; 50:1347-1354. [PMID: 32939957 DOI: 10.1111/hepr.13573] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 08/17/2020] [Accepted: 08/28/2020] [Indexed: 12/14/2022]
Abstract
AIM Tolvaptan is a newly available diuretic that has a specific function in water reabsorption inhibition. Given that spironolactone or furosemide induces the aggravation of cirrhotic hyponatremia and dehydration, tolvaptan affects the management strategy of liver cirrhosis. Representative predictive markers of its response include renal function-related markers such as urea nitrogen or creatinine. However, vascular function-related markers have not been well investigated. We investigated the effect of the vascular function-related marker asymmetric dimethylarginine (ADMA) and the effective arterial blood volume (EABV) marker, fractional excretion of sodium (FENa), on the early tolvaptan response and survival in liver cirrhosis. METHODS We prospectively recruited 49 patients who required add-on tolvaptan for refractory ascites or edema. Laboratory data were obtained immediately before and 1 day after tolvaptan administration. Patients exhibiting >1.5 kg weight loss after 1 week were categorized as early responders to tolvaptan. Patients were followed for a median of 200 days and were assessed for survival. RESULTS Early responders showed lower creatinine levels (<1.0 mg/dL), and higher ADMA levels (≥0.61 nmol/mL) than others in a multivariate analysis. Patients with a shorter survival were positive for hepatocellular carcinoma and had a low FENa (<0.35%). CONCLUSION Early responders showed higher ADMA levels reflecting vascular stricture, suggesting that higher vascular tonus is required for a tolvaptan early response. Patients with a shorter survival showed a lower FENa, reflecting a lower EABV and suggesting that adequate EABV is required for the prolonged survival after tolvaptan administration.
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Affiliation(s)
- Takuya Adachi
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan
| | - Akinobu Takaki
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan
| | - Shuichi Sato
- Department of Gastroenterology and Hepatology2, Shimane University Faculty of Medicine, Izumo, Shimane, Japan.,Department of Internal Medicine, Izumo City General Medical Center, Nadabun-cho, Izumo Shimane, Japan
| | - Hiroshi Tobita
- Department of Gastroenterology and Hepatology2, Shimane University Faculty of Medicine, Izumo, Shimane, Japan
| | - Haruhiko Kobashi
- Department of Hepatology, Japanese Red Cross Okayama Hospital, Kita-Ku, Okayama, Japan
| | - Masaru Kinomura
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan.,Department of Internal Medicine, Izumo City General Medical Center, Nadabun-cho, Izumo Shimane, Japan
| | - Atsuko Nakatsuka
- Department of Internal Medicine, Izumo City General Medical Center, Nadabun-cho, Izumo Shimane, Japan
| | - Atsushi Oyama
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan
| | - Nozomu Wada
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan
| | - Masahiro Sakata
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan
| | - Yasuto Takeuchi
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan
| | - Tetsuya Yasunaka
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan
| | - Hideki Onishi
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan
| | - Hidenori Shiraha
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan
| | - Hiroyuki Okada
- Departments of Gastroenterology and Hepatology, and Medical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama, Japan
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