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Abstract
Urea transport proteins were initially proposed to exist in the kidney in the late 1980s when studies of urea permeability revealed values in excess of those predicted by simple lipid-phase diffusion and paracellular transport. Less than a decade later, the first urea transporter was cloned. Currently, the SLC14A family of urea transporters contains two major subgroups: SLC14A1, the UT-B urea transporter originally isolated from erythrocytes; and SLC14A2, the UT-A group with six distinct isoforms described to date. In the kidney, UT-A1 and UT-A3 are found in the inner medullary collecting duct; UT-A2 is located in the thin descending limb, and UT-B is located primarily in the descending vasa recta; all are glycoproteins. These transporters are crucial to the kidney's ability to concentrate urine. UT-A1 and UT-A3 are acutely regulated by vasopressin. UT-A1 has also been shown to be regulated by hypertonicity, angiotensin II, and oxytocin. Acute regulation of these transporters is through phosphorylation. Both UT-A1 and UT-A3 rapidly accumulate in the plasma membrane in response to stimulation by vasopressin or hypertonicity. Long-term regulation involves altering protein abundance in response to changes in hydration status, low protein diets, adrenal steroids, sustained diuresis, or antidiuresis. Urea transporters have been studied using animal models of disease including diabetes mellitus, lithium intoxication, hypertension, and nephrotoxic drug responses. Exciting new animal models are being developed to study these transporters and search for active urea transporters. Here we introduce urea and describe the current knowledge of the urea transporter proteins, their regulation, and their role in the kidney.
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Affiliation(s)
- Janet D Klein
- Renal Division, Department of Medicine, Emory University, Atlanta, Georgia, USA
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Earley LE, Orloff J. THE MECHANISM OF ANTIDIURESIS ASSOCIATED WITH THE ADMINISTRATION OF HYDROCHLOROTHIAZIDE TO PATIENTS WITH VASOPRESSIN-RESISTANT DIABETES INSIPIDUS. J Clin Invest 2006; 41:1988-97. [PMID: 16695887 PMCID: PMC291129 DOI: 10.1172/jci104657] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Affiliation(s)
- L E Earley
- Laboratory of Kidney and Electrolyte Metabolism, National Heart Institute, Bethesda, Md
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Knepper MA, Valtin H, Sands JM. Renal Actions of Vasopressin. Compr Physiol 2000. [DOI: 10.1002/cphy.cp070313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Abstract
Urea is important for the conservation of body water due to its role in the production of concentrated urine in the renal inner medulla. Physiologic data demonstrate that urea is transported by facilitated and by active urea transporter proteins. The facilitated urea transporter (UT-A) in the terminal inner medullary collecting duct (IMCD) permits very high rates of transepithelial urea transport and results in the delivery of large amounts of urea into the deepest portions of the inner medulla where it is needed to maintain a high interstitial osmolality for concentrating the urine maximally. Four isoforms of the UT-A urea transporter family have been cloned to date. The facilitated urea transporter (UT-B) in erythrocytes permits these cells to lose urea rapidly as they traverse the ascending vasa recta, thereby preventing loss of urea from the medulla and decreasing urine-concentrating ability by decreasing the efficiency of countercurrent exchange, as occurs in Jk null individuals (who lack Kidd antigen). In addition to these facilitated urea transporters, three sodium-dependent, secondary active urea transport mechanisms have been characterized functionally in IMCD subsegments: (1) active urea reabsorption in the apical membrane of initial IMCD from low-protein fed or hypercalcemic rats; (2) active urea reabsorption in the basolateral membrane of initial IMCD from furosemide-treated rats; and (3) active urea secretion in the apical membrane of terminal IMCD from untreated rats. This review focuses on the physiologic, biophysical, and molecular evidence for facilitated and active urea transporters, and integrative studies of their acute and long-term regulation in rats with reduced urine-concentrating ability.
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Affiliation(s)
- J M Sands
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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STEIN RM, LEVITT BH, GOLDSTEIN MH, PORUSH JG, EISNER GM, LEVITT MF. The effects of salt restriction on the renal concentrating operation in normal, hydropenic man. J Clin Invest 1998; 41:2101-11. [PMID: 13983693 PMCID: PMC291144 DOI: 10.1172/jci104668] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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AUKLAND K. Renal tubular permeability to urea with special reference to accumulation of urea in the renal medulla. Scandinavian Journal of Clinical and Laboratory Investigation 1998; 13:646-60. [PMID: 13863278 DOI: 10.3109/00365516109137339] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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JAENIKE JR. Acute effects of the administration of vasopressin during water diuresis in the dog. J Clin Invest 1998; 42:161-70. [PMID: 13964442 PMCID: PMC289264 DOI: 10.1172/jci104702] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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THOMAS S. SOLUTE EXCRETION IN MAN DURING CHANGING URINE FLOW OCCURRING SPONTANEOUSLY AND INDUCED BY VASOPRESSIN INJECTION. J Clin Invest 1996; 43:1-10. [PMID: 14105227 PMCID: PMC289489 DOI: 10.1172/jci104883] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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YUNIS SL, BERCOVITCH DD, STEIN RM, LEVITT MF, GOLDSTEIN MH. RENAL TUBULAR EFFECTS OF HYDROCORTISONE AND ALDOSTERONE IN NORMAL HYDROPENIC MAN: COMMENT ON SITES OF ACTION. J Clin Invest 1996; 43:1668-76. [PMID: 14201550 PMCID: PMC441966 DOI: 10.1172/jci105042] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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GARDNER KD, MAFFLY RH. AN IN VITRO DEMONSTRATION IN INCREASED COLLECTING TUBULAR PERMEABILITY TO UREA IN THE PRESENCE OF VASOPRESSIN. J Clin Invest 1996; 43:1968-75. [PMID: 14236220 PMCID: PMC289641 DOI: 10.1172/jci105070] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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JAENIKE JR. THE RELATIVE RATES OF UREA AND WATER PERMEATION IN THE DISTAL NEPHRON OF THE INTACT KIDNEY. J Clin Invest 1996; 43:45-55. [PMID: 14105231 PMCID: PMC289495 DOI: 10.1172/jci104893] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Marsh DJ, Knepper MA. Renal Handling of Urea. Compr Physiol 1992. [DOI: 10.1002/cphy.cp080229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Imai M, Taniguchi J, Yoshitomi K. Osmotic work across inner medullary collecting duct accomplished by difference in reflection coefficients for urea and NaCl. Pflugers Arch 1988; 412:557-67. [PMID: 3211709 DOI: 10.1007/bf00583755] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
To demonstrate that osmotic work can be accomplished across the inner medullary collecting duct (IMCD) by the difference in reflection coefficients for urea and NaCl, phenomenological coefficients for urea and NaCl transport were determined in isolated segments of the hamster IMCD perfused in vitro. Arginine vasopressin at 100 microU/ml increased urea permeability from 11.5 +/- 2.9 to 31.7 +/- 4.2 x 10(-7) cm2 s-1 in the middle IMCD but not in the upper IMCD. Urea transport in the middle IMCD consisted of two components, transport with saturable kinetics and simple passive diffusion. Permeability to Na+ was very low (2 x 10(-7) cm2 s-1). Reflection coefficients as measured by the equiosmolality method, with raffinose being a reference solute, were 0.87 +/- 0.05 and 0.71 +/- 0.04 for urea and 1.03 +/- 0.07 and 0.91 +/- 0.04 for NaCl in the upper and the middle IMCD, respectively. Reflection coefficient for urea in the middle IMCD was 0.68 when determined by the zero volume flux method. When the middle IMCD was perfused with bicarbonate Krebs-Ringer (BKR) solution containing 200 mmol/l urea, the replacement of urea in the bathing fluid with equisomolal NaCl caused large volume flux (3.81 +/- 0.45 nl mm-1 min-1) associated with dilatation of intercellular space. The existence of vasopressin in the bath was essential for this phenomenon. This effect was inhibited by 5 x 10(-4) M phloretin in the bath, suggesting that the vasoressin-stimulated urea transport is responsible for this phenomenon. From these observations, we conclude that transport parameters of the middle IMCD are appropriate for accomplishment of osmotic work across this segment in the absence of physicochemical osmotic gradients.
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Affiliation(s)
- M Imai
- Department of Pharmacology, National Cardiovascular Center, Osaka, Japan
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Kirk CJ, Creba JA, Hawkins PT, Michell RH. Is vasopressin-stimulated inositol lipid breakdown intrinsic to the mechanism of Ca2+-mobilization at V1 vasopressin receptors? PROGRESS IN BRAIN RESEARCH 1983; 60:405-11. [PMID: 6320275 DOI: 10.1016/s0079-6123(08)64407-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Lacy ER, Schmidt-Nielsen B. Anatomy of the renal pelvis in the hamster. THE AMERICAN JOURNAL OF ANATOMY 1979; 154:291-320. [PMID: 433785 DOI: 10.1002/aja.1001540302] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The hamster renal pelvis has been studied by means of low-power light microscopy, scanning electron microscopy and morphometric analyses. The results of this study are highly suggestive that the contact of pelvic urine with the other medulla as well as with the inner medulla may be an important aspect of final urine formation. The outer medulla constituted nearly 50% of the total pelvic surface area, with the inner stripe of the outer medulla more than twice the pelvic surface area of the outer stripe of the outer medulla. The large outer medullary pelvic surface area was accounted for by the elaboration of the upper pelvic walls into peripelvic columns, opercula ("secondary pyramids"), fornices and secondary pouches. A thin simple-squamous to low cuboidal pelvic epithelium separated pelvic urine from outer medullary parenchyma. The inner medulla which constituted about one quarter of the total pelvic surface area was covered by a cuboidal to columnar pelvic epithelium which appeared morphologically similar to the papillary collecting duct epithelium. Tubules and capillaries of the inner medulla did not appear as closely juxtaposed to the pelvic epithelium as did those of the outer medulla. Cortical tissue comprised only 11.7% of the total pelvic surface area and was covered by transitional epithelium similar to that of ureter and bladder. The previously reported impermeability of this epithelium suggests that pelvic urine contact with the cortex is unimportant in final urine formation. The rich layer of smooth muscle under the transitional epithelium probably functions to move urine into and out of the pelvis during pelvic peristalsis, which has been observed in vivo.
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Sanjana VM, Robertson CR, Jamison RL. Water extraction from the inner medullary collecting tubule system: a role for urea. Kidney Int 1976; 10:139-46. [PMID: 966451 DOI: 10.1038/ki.1976.87] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Recent examinations of the inner medullary collecting tubule membrane in vitro have demonstrated that its reflection coefficient to urea (sigma urea) is significantly less than unity and less than sigma NaClhe presence of antidiuretic hormone. Fluid entering the inner medullary collecting tubule has a higher urea concentration and lower NaCl concentration than does the medullary interstitium, although total osmolarity is nearly equal on either side of the membrane. The transtubular difference in solute composition, together with the difference between sigma urea and sigma NaCl, should result in a driving force for extraction of water from the tubule. This hypothesis was examined in a differential analysis of water and solute fluxes across the collecting tubule epitheliu. The results indicate that this driving force contributes significantly to water extraction from the inner medullary collecting tubule.
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Tisher CC, Yarger WE. Lanthanum permeability of tight junctions along the collecting duct of the rat. Kidney Int 1975; 7:35-44. [PMID: 1127864 DOI: 10.1038/ki.1975.5] [Citation(s) in RCA: 45] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The permeability of the tight junctions (zonulae occludentes) was evaluated along the entire length of the collecting duct of the rat using a lanthanum tracer technique. Nine rats with hereditary hypothalamic diabetes insipidus were studied using standard micropuncture and clearance techniques. Glomerular filtration rate (GFR) estimated from inulin clearance, urine and plasma osmolality (U/Posm) and urine flow rate (V) were determined in eight of nine animals. During either sustained diuresis (five animals) or vasopressin-induced antidiuresis (four animals), individual surface convolutions of distal convoluted tubules or early cortical collecting ducts were preserved for ultrastructural examination by intraluminal microperfusion with a glutaraldehyde-formaldehyde fixative followed by a second microperfusion with a lanthanum tracer. Mean GFR during diuresis was 6.31 plus or minus se 0.63 ml/min/kg of body wt and v=797 plus or minus se 108 mul/min/kg or 13.6 plus or minus se 2.2% of the filtered load of water. After administration of exogenous vasopressin, V fell to 311 plus or minus 157 mul/min/kg or 5.2 plus or minus se 3.8% of the filtered load of water and U/Posm rose from 0.658 plus or minus se 0.043 to 2.124 plus or minus 0.454. Tight junctions of cortical and outer medullary segments of the collecting duct resisted lanthanum penetration. Tight junctions of the inner medullary and papillary segments of the collecting duct were freely permeable to lanthanum suggesting the presence of a paracellular shunt pathway for solute and water movement. The results were independent of the presence or absence of vasopressin. Physiological studies have previously demonstrated that cortical and outer medullary segments of the collecting duct have a low urea permeability while inner medullary and papillary segments of the collecting duct have a relatively high urea permeability. The possibility is suggested that urea movement across the inner medullary and papillary segments of the collecting duct may occur, at least in part, via a paracellular pathway formed by the nonoccluding tight junction and the lateral intercellular space.
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Atherton JC, Green R, Thomas S, Wood JA. Time course of changes in renal tissue and urinary composition after cessation of constant infusion of lysine vasopressin in the conscious, hydrated rat. J Physiol 1972; 222:583-95. [PMID: 5033024 PMCID: PMC1331402 DOI: 10.1113/jphysiol.1972.sp009816] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
1. The changes in urinary and renal tissue composition in conscious rats were determined for up to 2 hr following the cessation of intravenous infusion of lysine vasopressin, LVP (at 60 muu./min. 100 g body wt. for 4(1/2) hr). A constant water load (4% body wt.) was maintained during and after lysine vasopressin infusion, by quantitative replacement of excreted water. In these circumstances, any changes in urinary and renal tissue composition are presumed to represent direct consequences of the rapid plasma and tissue clearance of lysine vasopressin.2. Urinary flow increased and osmolality decreased, rapidly, reaching stable values characteristic of sustained water diuresis after about 60 min.3. The steepness of the corticomedullary solute concentration gradients also decreased rapidly. Papillary Na and urea concentrations fell to values characteristic of sustained water diuresis in about 45 min.4. The changes in medullary composition were compounded of a moderate significant increase in water content, a moderate, significant decrease in Na content, and a profound decrease in urea content.5. In the eventual steady-state water diuresis, urinary outputs of Na and K were significantly lower, and of NH(4) significantly higher, than those observed in control experiments where LVP infusion was continued for the corresponding 2 hr.6. It is concluded that the diuresis following the cessation of LVP infusion is due not merely to reduced nephron permeability to water but also to a rapid reduction in the osmotic force responsible for water reabsorption from the collecting duct.
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Abstract
1. To find how urea contributes to the water-conserving ability of a herbivore's kidney, groups of ten young rabbits on a low-protein diet and at three different levels of dietary electrolyte were given 1.8 g urea by mouth daily for 3 days. Vasopressin was administered daily to half the animals in each group.2. The urinary osmolarity and urea output of each animal was recorded daily during the urea loading and for a 3-day control period before and after loading. The renal water requirement for non-urea solute output (defined as daily volume/daily non-urea solute output) was calculated. The sodium content of renal cortex and medulla was measured in some animals from each group.3. Urea caused additional water excretion only in those rabbits which were receiving the low-salt diet. There was invariably increased water excretion when the ratio of urea to non-urea solute output exceeded 2.4. In most of the rabbits on normal-salt and high-salt intake, urea produced little change in the volume in which non-urea solute was excreted. Three out of the ten high-salt animals showed significant reduction of this volume during urea-loading.5. Vasopressin significantly reduced the volume required for non-urea solute output, but the effect of vasopressin was independent of urea-loading and of dietary electrolyte level.6. The low-electrolyte diet significantly reduced the sodium concentration in the rabbits' renal medullary tissue.7. It is concluded that in rabbits urea contributes to water retention mainly by its high permeability, enhanced by vasopressin, which permits maximal water reabsorption in the renal medulla. Water retention by means of uphill transport of urea, if it occurs at all, is slight.
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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. The time course of changes in renal tissue composition during mannitol diuresis in the rat. J Physiol 1968; 197:411-28. [PMID: 5716851 PMCID: PMC1351807 DOI: 10.1113/jphysiol.1968.sp008567] [Citation(s) in RCA: 38] [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 the composition of renal tissue slices in osmotic diuresis were determined by sacrificing groups of rats before and during the intravenous infusion of mannitol (15 g/100 ml.) for up to 7(1/2) hr.2. Very rapid changes in tissue water and solute contents occurred within 15 min, preceding the times of maximal diuresis, with little subsequent change even up to 7(1/2) hr.3. The main changes were:(a) an increase in water content in all slices, particularly the papilla; (b) a very profound decrease in papillary and medullary urea content in the first 15 min, with a small, but significant, further decrease, subsequently; (c) a small, but significant, rapid decrease in papillary sodium, and small non-significant increases in the outer medulla and cortex. Subsequent changes in any segment were small and non-significant; (d) apart from small changes in the first 15 min ammonium and potassium contents remained fairly constant.4. The rates of change in papillary and urinary urea concentrations were similar, so that after 30 min, any differences between tip and urinary concentrations were small and non-significant.5. The findings are discussed in terms of factors influencing counter-current mechanisms. It is concluded that altered medullary blood flow is mainly responsible for the rapid changes in medullary composition.6. The relation between papillary and urinary urea concentrations is explicable in terms of passive handling, with equilibration across a freely permeable collecting duct membrane.
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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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Goldberg M, Wojtczak AM, Ramirez MA. Uphill transport of urea in the dog kidney: effects of certain inhibitors. J Clin Invest 1967; 46:388-99. [PMID: 6023774 PMCID: PMC297059 DOI: 10.1172/jci105540] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
To study the renal medullary transport and accumulation of urea in dogs independent of water transport, we obliterated the medullary electrolyte gradient by a sustained ethacrynic acid diuresis. Infusions of urea were also given at various rates to vary urinary urea concentration. In the steady state, the kidneys were removed, and slices were analyzed for water, urea, and electrolytes. In every experiment in 15 dogs over a range of urinary urea concentration from 19 to 230 mmoles per L and urine flow from 0.5 to 9.7 ml per minute per kidney, an intrarenal urea gradient persisted, and urinary urea concentration was always lower than papillary water urea concentration. The magnitude of this uphill urinary-papillary gradient (mean +/- SE = - 21 +/- 2.9 mmoles per L) was not affected by hemorrhagic hypotension or a nonprotein diet. In 12 additional experiments begun similarly, inhibitors were infused into one renal artery. Both iodoacetate, an inhibitor of anaerobic glycolysis, and acetamide, an analogue of urea, markedly and significantly reduced both the intrarenal urea gradient and the uphill urinary-papillary gradient. In contrast, cyanide, an inhibitor of oxidative metabolism, had no observable effect on the urea gradients. The data are best explained by postulating an active transport system for urea in the medullary collecting duct deriving its energy from anaerobic glycolysis.
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Dormandy TL, Robinson A, Wright ED. Active renal water excretion. Lancet 1967; 1:246-8. [PMID: 4163149 DOI: 10.1016/s0140-6736(67)91305-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Abstract
The isotopic equilibration of urea, thiourea, and inulin between urine and plasma was determined in rabbits in the presence or absence of antidiuretic hormone (ADH). Animals were anesthetized with ethanol and permitted to reach steady state after completion of surgery. Tracer was then administered by intraarterial infusion in such a manner that a high constant specific activity in plasma was rapidly attained. Urine flow was kept independent of ADH by addition of mannitol. Urea/creatinine clearance ratios and the accumulation of urea in renal medulla and papilla also remained unaffected by ADH. Under these conditions, thiourea and inulin at all times approached equilibrium, at similar rates. In the absence of ADH, urea also equilibrated at a rate similar to that of inulin. The addition of ADH, however, significantly prolonged the delay before urinary urea reached the high constant specific activity of plasma urea. These observations are interpreted in terms of a specific effect of the hormone on the solute permeability of the nephron.
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Anastasakis S, Buchborn E. [Disorders of urine concentration in chronic nephropathies]. KLINISCHE WOCHENSCHRIFT 1966; 44:288-98. [PMID: 5987546 DOI: 10.1007/bf01752275] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Valtin H. Sequestration of urea and nonurea solutes in renal tissues of rats with hereditary hypothalamic diabetes insipidus: effect of vasopressin and dehydration on the countercurrent mechanism. J Clin Invest 1966; 45:337-45. [PMID: 5904551 PMCID: PMC292703 DOI: 10.1172/jci105348] [Citation(s) in RCA: 110] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
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Capek K, Fuchs G, Rumrich G, Ullrich KJ. Harnstoffpermeabilit�t der corticalen Tubulusabschnitte von Ratten in Antidiurese und Wasserdiurese. Pflugers Arch 1966. [DOI: 10.1007/bf00363128] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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37
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Chemical pathology in relation to clinical medicine RENAL FUNCTION: The proceedings of a symposium organized by the Association of Clinical Pathologists held in London at the Westminster Hospital 16-17 October 1964. Clin Mol Pathol 1965; 18:491-578. [PMID: 16811025 PMCID: PMC473000 DOI: 10.1136/jcp.18.4.491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
38
|
Mertz DP. [On the problem of participation of non-electrolytes (urea, creatinine) in the process of urine concentration in man]. KLINISCHE WOCHENSCHRIFT 1965; 43:661-73. [PMID: 5838499 DOI: 10.1007/bf01728704] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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39
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40
|
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41
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MERTZ DP, SARRE H, CREMER Z. �ber den diagnostischen Wert semiquantitativer Nierenfunktionsproben. ACTA ACUST UNITED AC 1962; 40:889-93. [PMID: 14472905 DOI: 10.1007/bf01482931] [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: 10/25/2022]
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42
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Untersuchungen �ber den Transportmechanismus von Harnstoff-Stickstoff durch die Pansenschleimhaut von Rindern in vitro. Pflugers Arch 1962. [DOI: 10.1007/bf00362611] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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43
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GAERTNER K. [Studies on the mechanism of urea-nitrogen transport through the mucosa of cattle rumen in vitro]. PFLUGERS ARCHIV FUR DIE GESAMTE PHYSIOLOGIE DES MENSCHEN UND DER TIERE 1962; 276:292-302. [PMID: 13946084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/24/2023]
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