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Sparks MA, Stegbauer J, Chen D, Gomez JA, Griffiths RC, Azad HA, Herrera M, Gurley SB, Coffman TM. Vascular Type 1A Angiotensin II Receptors Control BP by Regulating Renal Blood Flow and Urinary Sodium Excretion. J Am Soc Nephrol 2015; 26:2953-62. [PMID: 25855778 DOI: 10.1681/asn.2014080816] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 01/27/2015] [Indexed: 01/10/2023] Open
Abstract
Inappropriate activation of the type 1A angiotensin (AT1A) receptor contributes to the pathogenesis of hypertension and its associated complications. To define the role for actions of vascular AT1A receptors in BP regulation and hypertension pathogenesis, we generated mice with cell-specific deletion of AT1A receptors in smooth muscle cells (SMKO mice) using Loxp technology and Cre transgenes with robust expression in both conductance and resistance arteries. We found that elimination of AT1A receptors from vascular smooth muscle cells (VSMCs) caused a modest (approximately 7 mmHg) yet significant reduction in baseline BP and exaggerated sodium sensitivity in mice. Additionally, the severity of angiotensin II (Ang II)-dependent hypertension was dramatically attenuated in SMKO mice, and this protection against hypertension was associated with enhanced urinary excretion of sodium. Despite the lower BP, acute vasoconstrictor responses to Ang II in the systemic vasculature were largely preserved (approximately 80% of control levels) in SMKO mice because of exaggerated activity of the sympathetic nervous system rather than residual actions of AT1B receptors. In contrast, Ang II-dependent responses in the renal circulation were almost completely eliminated in SMKO mice (approximately 5%-10% of control levels). These findings suggest that direct actions of AT1A receptors in VSMCs are essential for regulation of renal blood flow by Ang II and highlight the capacity of Ang II-dependent vascular responses in the kidney to effect natriuresis and BP control.
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Affiliation(s)
- Matthew A Sparks
- Division of Nephrology, Department of Medicine, Durham VA and Duke University Medical Centers, Durham, North Carolina
| | - Johannes Stegbauer
- Division of Nephrology, Department of Medicine, Durham VA and Duke University Medical Centers, Durham, North Carolina; Department of Nephrology, Medical Faculty, University Hospital Düsseldorf, Düsseldorf, Germany
| | - Daian Chen
- Division of Nephrology, Department of Medicine, Durham VA and Duke University Medical Centers, Durham, North Carolina
| | - Jose A Gomez
- Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, North Carolina; and
| | - Robert C Griffiths
- Division of Nephrology, Department of Medicine, Durham VA and Duke University Medical Centers, Durham, North Carolina
| | - Hooman A Azad
- Division of Nephrology, Department of Medicine, Durham VA and Duke University Medical Centers, Durham, North Carolina
| | - Marcela Herrera
- Division of Nephrology, Department of Medicine, Durham VA and Duke University Medical Centers, Durham, North Carolina
| | - Susan B Gurley
- Division of Nephrology, Department of Medicine, Durham VA and Duke University Medical Centers, Durham, North Carolina
| | - Thomas M Coffman
- Division of Nephrology, Department of Medicine, Durham VA and Duke University Medical Centers, Durham, North Carolina; Cardiovascular and Metabolic Disorders Research Program, Duke-National University of Singapore, Graduate Medical School, Singapore
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Franchini KG. Hemodilution mediates changes in renal hemodynamics after acute volume expansion in rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:R1670-6. [PMID: 9608022 DOI: 10.1152/ajpregu.1998.274.6.r1670] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The present study examined the factors responsible for triggering renal hemodynamic adjustments during acute volume expansion. The renal hemodynamic effects of graded volume expansion with 0.9% saline (Sal; 1, 2, and 4% of body wt), 7% BSA solution (0.35, 0.70, and 1.4% body wt), or whole blood from a donor rat (WBL; 0.35, 0.70, and 1.4% body wt) were compared in rats anesthetized with pentobarbital sodium. Neural influences on the kidney were eliminated by vagus nerves, baro/chemoreceptor afferents, and renal nerves section, and renal perfusion pressure was controlled at constant level (approximately 120 mmHg) throughout the experiments. In Sal- and BSA-expanded rats, renal blood flow (RBF) increased (Sal: 15, 40, 71%; BSA 17, 49, 107%) and renal vascular resistance (RVR) decreased in parallel with the degree of volume expansion (RVR: Sal 17, 31, 44%; and BSA: 15, 35, 54%). Renal hemodynamics remained unaltered after expansion with WBL. In rats expanded with Sal or BSA, correction of the fall of hematocrit restored RBF and RVR to control levels. Interference with tubuloglomerular feedback by uretheral obstruction had no effect on the decrease in RVR with Sal or BSA. Inhibition of the vascular tone by intrarenal papaverine infusion also did not alter the renal hemodynamic response to volume expansion with Sal or BSA. These findings suggest that the changes in renal hemodynamics after acute expansion are likely mediated by changes in rheologic properties of the blood rather than by changes in active vascular tone.
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Affiliation(s)
- K G Franchini
- Departamento de Clinica Médica, Faculdade de Ciencias Médicas, Universidade Estadual de Campinas, 13081-970 Campinas, São Paulo, Brazil
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Boer WH, Koomans HA, Dorhout Mees EJ. Renal lithium handling during water loading and subsequent d-DAVP-induced anti-diuresis. Eur J Clin Invest 1988; 18:273-8. [PMID: 3138130 DOI: 10.1111/j.1365-2362.1988.tb01258.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Assuming that lithium is exclusively reabsorbed in the proximal tubules pari passu with sodium (Na), the lithium clearance (CLi) has been advanced as an index of filtrate delivery from the proximal tubules. In order to determine whether water loads in a range commonly given during clearance studies affect CLi, we studied nine normal subjects (Na intake 150 mmol day-1) on three water loads resulting in stable urine flow rates of 2.2 +/- 0.9, 6.1 +/- 0.7 and 11.7 +/- 3.0 ml min-1, respectively. We also studied the effect of acute anti-diuresis (urine flow less than 1 ml min-1) induced by d-DAVP given i.v. at the end of all studies. Water loading up to induction of maximum water diuresis did not significantly affect absolute or fractional CLi. Sodium and chloride excretion were reduced at the highest water intake level. Administration of d-DAVP caused a 50% reduction in fractional Na excretion and a small but significant rise in fractional lithium reabsorption from 75.5 +/- 3.9 to 77.5 +/- 3.6%. We conclude that CLi is hardly affected over a wide range of water intakes and urine flow rates, despite concomitant changes in Na excretion. The finding that d-DAVP, which probably enhances Na reabsorption in the thick ascending limb of Henle's loop, also enhanced lithium reabsorption, suggests that lithium may be partly reabsorbed in this nephron segment. Thus, lithium may not be the exact, quantitative marker of Na reabsorption in the proximal tubules that it is purported to be.
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Affiliation(s)
- W H Boer
- Department of Nephrology and Hypertension, University Hospital, Utrecht, The Netherlands
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Ikeda N, Marumo F, Shirataka M, Sato T. A model of overall regulation of body fluids. Ann Biomed Eng 1979; 7:135-66. [PMID: 533022 DOI: 10.1007/bf02363132] [Citation(s) in RCA: 39] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Alexander EA, Doner DW, Auld RB, Levinsky NG. Tubular reabsorption of sodium during acute and chronic volume expansion in man. J Clin Invest 1972; 51:2370-9. [PMID: 4639021 PMCID: PMC292404 DOI: 10.1172/jci107049] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Renal hemodynamics and tubular fractional sodium reabsorption (FSR) were evaluated by clearance techniques during acute and chronic extracellular volume expansion in man. (1 - V/GFR) x 100 was used as an index of proximal and (C(H2O)/V) x 100 as an estimate of distal fractional reabsorption. After acute loading with isotonic saline 37 ml/kg body wt, proximal FSR decreased by 4.8% and distal FSR decreased by 4.4%. After comparable chronic expansion by mineralocorticoids ("escape"), proximal FSR also decreased by 3.9%, but distal reabsorption was not altered.In separate studies, subjects were progressively infused with saline to 57 (E(1)) and to 80 (E(2)) ml/kg body wt, and appeared to divide into "excreters" (maximum U(Na)V > 1000 muEq/min) and "nonexcreters" (maximum U(Na)V < 550 muEq/min). In the excreters, GFR rose, proximal FSR decreased by 7.1% after E(1) and only 0.9% further after E(2). Distal FSR fell by 14.8% after E(1) and by an additional 4.9% after E(2). In the nonexcreters, GFR was stable and proximal FSR did not fall significantly after E(1) or E(2). Distal FSR decreased 4.5% after E(1) and 1.3% further after E(2). It is concluded that both acute and chronic extracellular expansion decrease proximal FSR in man, but only acute loading depresses distal FSR. Ability of some men to excrete sodium rapidly after acute infusion is related to larger increases in GFR and greater decreases in both proximal and distal FSR than occur in men in whom natriuresis is more limited.
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Schrier RW, De Wardener HE. Tubular reabsorption of sodium ion: influence of factors other than aldosterone and glomerular filtration rate. 1. N Engl J Med 1971; 285:1231-43. [PMID: 4939799 DOI: 10.1056/nejm197111252852205] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Cannon PJ, Svahn DS, Demartini FE. The influence of hypertonic saline infusions upon the fractional reabsorption of urate and other ions in normal and hypertensive man. Circulation 1970; 41:97-108. [PMID: 5420637 DOI: 10.1161/01.cir.41.1.97] [Citation(s) in RCA: 51] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Renal hemodynamics and the excretion rates of six ions were studied in a group of 24 normotensive and hypertensive subjects during expansion of extracellular fluid volume (ECF) with intravenous infusions of hypertonic saline. In response to the 2.5% saline infusions arterial blood pressure did not change from control values, but glomerular filtration rate increased, and renal vascular resistance decreased.
Accompanying these hemodynamic alterations the urinary excretion rates of sodium, calcium, magnesium, potassium, chloride, and urate increased significantly. Net fractional reabsorption of the six ions fell significantly below control values. The induced changes in net Ca, Mg, K, Cl, and urate reabsorption in all the subjects were directly and significantly related to the simultaneous depression of Na reabsorption.
The data indicate that increased excretion and net tubular rejection of urate accompany depression of tubular sodium reabsorption during hypertonic saline infusions in normal and hypertensive man. The nonspecificity of depressed fractional ion reabsorption during the infusions is compatible with the hypothesis that physical forces which alter fluid uptake by peritubular capillaries determine to a significant extent the natriuretic response of the human nephron to hypertonic saline infusions. Alternatively, if a natriuretic hormone elicited by ECF volume expansion in man accounts for the depressed fractional Na reabsorption, the data imply that directly or indirectly this substance inhibits net fractional reabsorption of a variety of other ions.
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Bonjour JP, Peters G. Non-occurrence of a natriuretic factor in circulating blood of rats after expansion of the extracellular or the intravascular space. Pflugers Arch 1970; 318:21-34. [PMID: 5463914 DOI: 10.1007/bf00588540] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Aperia A, Broberger O, Ericsson NO, Feychting H. Renal function in man during transition from hydropenia to water diuresis with superimposed mannitol load. ACTA PHYSIOLOGICA SCANDINAVICA 1969; 77:429-38. [PMID: 5376866 DOI: 10.1111/j.1748-1716.1969.tb04586.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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11
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Hai MA, Thomas S. Influence of prehydration on the changes in renal tissue composition induced by water diuresis in the rat. J Physiol 1969; 205:599-618. [PMID: 5361291 PMCID: PMC1348571 DOI: 10.1113/jphysiol.1969.sp008985] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
1. The composition of renal tissue was determined in rats before and immediately after intravenous infusion of dextrose (2.5 g/100 ml.) in amounts sufficient to administer a positive fluid load of 4% body weight over 2 hr. The rats were classified into three groups, according to the preinfusion urine osmolality: hydropaenia, normal and moderately diuretic (over 2400, 800-1500 and below 800 mu-osmoles/g H(2)O, respectively).2. In non-infused rats, the steepness of the corticomedullary osmolal gradient varied, due to differences in both water and solute (sodium and urea) contents, and was related to urinary osmolality. Whereas differences in medullary and papillary solute contents occurred between all three groups, papillary water content was significantly higher only in the moderately diuretic animals.3. Dextrose infusion caused the induction of water diuresis, the lowest urinary osmolalities being produced in the previously moderately diuretic animals.4. Dextrose infusion caused a considerable reduction in the steepness of the corticomedullary osmolal gradient in all rats, particularly in the previously hydropaenic animals, due to changes in both solute (sodium and urea) and water contents. Whereas reductions in medullary and papillary solute contents occurred in all three groups, there was no further increase in papillary water content from the already high values seen in the noninfused diuretic animals.5. Thus, dextrose infusion largely abolished any previous differences in tissue water content, whereas significant, though small, differences in osmolal (particularly urea) content persisted.6. These data are discussed in terms of changes and differences in endogenous antidiuretic hormone (A.D.H.) release.7. Changes in the magnitude and direction of the urinary-papillary urea concentration difference are discussed in terms of passive transport, with probable A.D.H.-induced changes in nephron urea permeability.
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Hutchin P, Terzi RG, Hollandsworth LC, Johnson G, Peters RM. The influence of intravenous fluid administration on postoperative urinary water and electrolyte excretion in thoracic surgical patients. Ann Surg 1969; 170:813-23. [PMID: 5347558 PMCID: PMC1387660 DOI: 10.1097/00000658-196911000-00013] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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13
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Mullane JF, Gliedman ML. Acute renal vein hypertension: oliguria, hormone infusion, and volume expansion. J Surg Res 1969; 9:247-53. [PMID: 4304581 DOI: 10.1016/0022-4804(69)90061-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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14
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McGiff JC, Lynch JR, Leinicke JA, Strand JC, Aboosi A. Some determinants of the effects of VAL-5-angiotensin II amide on glomerular filtration rate and sodium excretion in dogs. J Clin Invest 1969; 48:146-55. [PMID: 4303789 PMCID: PMC322200 DOI: 10.1172/jci105963] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In 12 dogs anesthetized with chloralose, angiotensin (angiotensin II amide) given intravenously increased the glomerular filtration rate (GFR) of an ischemic kidney while simultaneously having little effect on the GFR of the contralateral kidney. In the ischemic kidney, in 14 of 30 observations, increments of GFR greater than 100% of mean control GFR (9 ml/min) occurred in response to angiotensin. The magnitude of the increase in GFR produced by angiotensin was independent of dose (range 0.005-0.050 mug/kg per min), the degree of accompanying pressor response, and alterations in renal blood flow (RBF) (electromagnetic flow-meter). In the ischemic kidney, increments of GFR could be produced by sub-pressor doses of angiotensin. Dissociations between increments of GFR and sodium excretion occurred. Equivalent increments of GFR in the ischemic kidney in dogs receiving either 5% glucose in water or 10% mannitol in 0.3% saline were associated with natriuresis only in the latter group: a) as an initial response of the contralateral kidney to renal arterial constriction (RAC) in spite of a concomitant reduction in RBF and an unchanged GFR; b) in the ischemic kidney on giving angiotensin. The natriuresis produced by angiotensin was independent of the magnitude of elevations in blood pressure, altered filtration fraction, and was associated with a further reduction in RBF. After release of RAC in the dogs receiving mannitol, an antinatriuresis was again observed in response to angiotensin. The presence of unilateral renal ischemia allowed the demonstration of a differential action of angiotensin on the GFR of an ischemic and nonischemic kidney. The natriuresis in response to angiotensin requires, in addition to mannitol, the participation of undefined factors invoked by unilateral renal ischemia.
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Metzger RA, Vaamonde LS, Vaamonde CA, Papper S. Renal excretion of sodium during oral water administration in patients with systemic hypertension. Circulation 1968; 38:955-64. [PMID: 5697692 DOI: 10.1161/01.cir.38.5.955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The renal excretion of sodium and water was studied in 10 hypertensive subjects following an oral sustained 20 ml/kg water load. The study was performed under conditions controlled for sodium content of the diet, time of the day, and posture; the urine was collected by spontaneous voiding. The results were compared with those obtained from 10 normotensive subjects studied under similar conditions.
The increased urine flow following the water load in the hypertensive subjects was not accompanied by increased excretion of sodium, a pattern similar to the one observed in the normotensive subjects.
Comparing the group of hypertensive subjects with previously studied normotensives revealed the following additional information. The hypertensive subjects responded to water administration by increasing volume and C
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more rapidly than the normotensives; however, the maximal response was not significantly different. The fractional reabsorption of sodium was less in the hypertensive subjects despite a lower filtered load of sodium. This suggests a difference in the renal tubular handling of sodium between hypertensive and normotensive subjects.
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Atherton JC, Hai MA, Thomas S. The time course of changes in renal tissue composition duruig water diuresis in the rat. J Physiol 1968; 197:429-43. [PMID: 5716852 PMCID: PMC1351808 DOI: 10.1113/jphysiol.1968.sp008568] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
1. The time course and extent of changes in the composition of renal tissue slices in water diuresis were determined by sacrificing groups of rats before and during the intravenous infusion of dextrose (2.5 g/100 ml.) in amounts sufficient to administer over 2 hr, and subsequently to maintain for up to 7(1/2) hr, a positive fluid load of 4% body weight.2. The corticomedullary osmolal gradient characteristic of the nondiuretic rats was progressively dissipated until, at 7(1/2) hr, only papillary tip concentrations were higher than those of other segments.3. The changes in individual constituents followed different time courses: (i) an increase in water content in all segments, particularly the papilla, was almost complete by 1 hr, preceding the maximal increases in urine flow; (ii) a marked decrease in papillary and medullary urea content in the first hour was followed by a slower, progressive decrease leading to an almost complete dissipation of the urea gradient by 7(1/2) hr; (iii) small, non-significant decreases in sodium content occurred in all segments in the first hr, followed by a further small, progressive decrease in papillary sodium content; (iv) changes in ammonium and potassium concentrations were mainly related to those in water content, since the contents of these solutes showed only small changes.4. By 2 hr, differences in the rates of decline of osmolal and urea concentrations in urine and papilla led to urinary concentrations significantly lower than papillary values. The steep papilla-urine urea concentration difference became smaller, but remained significant even at 7(1/2) hr.5. The findings are discussed in terms of changes in countercurrent mechanisms, particularly as influenced by anti-diuretic hormone.6. The development of papilla/urine urea concentration ratio greater than unity is also considered in terms of passive transport with changes in membrane permeability.
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Atherton JC, Hai MA, Thomas S. Effects of water diuresis and osmotic (mannitol) diuresis on urinary solute excretion by the conscious rat. J Physiol 1968; 197:395-410. [PMID: 5716850 PMCID: PMC1351806 DOI: 10.1113/jphysiol.1968.sp008566] [Citation(s) in RCA: 39] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
1. The time course and extent of changes in urinary flow and in the outputs of urea, Na(+), K(+), and NH(4) (+) over a period of 7(1/2) hr in conscious rats during water and osmotic (mannitol) diuresis were determined, and compared with spontaneous changes in non-diuretic animals.2. In non-diuretic rats, a morning rise and subsequent decline in urinary osmolal, sodium, potassium and ammonium outputs occurred, possibly attributable to circadian rhythms.3. Water diuresis was accompanied by (i) a rapid increase in urea excretion during the phase of increasing urine flow, followed by a fall in later periods to values similar to those in non-diuresis, (ii) a slower increase in sodium output, continuing after the establishment of the constant water load, (iii) unchanged potassium excretion, but slightly increased ammonium outputs.4. Mannitol diuresis was accompanied by (i) a rapid increase in urea outputs which subsequently fell but remained significantly higher, (ii) a steep rise in sodium and potassium outputs to values which remained far higher than those in non-diuretic and water diuretic animals.5. The changes in mannitol diuresis are considered to result mainly from decreased tubular reabsorption, due to the lowered intraluminal sodium, potassium and urea concentrations and increased intratubular fluid flow. Some of the acute increase in urea excretion may be due to washout of medullary urea into the tubular fluid.6. In water diuresis, some of the changes in solute excretion may similarly result from altered tubular reabsorption, perhaps influenced by suppression of anti-diuretic hormone (A.D.H.). In addition, the slower changes in sodium output may be related to several consequences of change in body fluid volume.
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Cannon PJ. Effects of five per cent dextros-water infusions in normal and hypertensive man. Evidence for increased proximal and distal tubular sodium rejection by hypertensive patients and its relation to renal hemodynamics. Circulation 1968; 37:832-46. [PMID: 4869293 DOI: 10.1161/01.cir.37.5.832] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
During infusions of 5% dextrose in water urinary sodium excretion and the renal tubular rejection of filtered sodium (E/F Na %) were significantly higher in hypertensive than in normotensive subjects. Increased E/F Na % did not result from alterations in plasma sodium, in filtered sodium, or from an osmotic diuresis.
Fractional sodium reabsorption in proximal (isosmotic) portions of the nephron was diminished in the hypertensive patients. Free water formation (C
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o
rose with increased "distal" sodium delivery (V) in both groups; however, fractional sodium reabsorption in the "distal" nephron was significantly impaired in the hypertensive patients and urinary osmolality was increased.
Mean arterial blood pressure and E/F Na % were related in curvilinear fashion in the 31 studies, and there was a direct relation between E/F Na % and the magnitude of renal vascular resistance. The data suggested that alterations of renal arterial pressure and vascular resistance in hypertensive disease modify sodium transport in proximal and diluting segments of the nephron and determine to a major extent the increased natriuresis exhibited by hypertensive subjects during infusions that expand extracellular fluid volume.
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