Interactions between ADH and prostaglandins in isolated erythrocyte-perfused rat kidney

1987 ◽  
Vol 252 (2) ◽  
pp. F331-F337 ◽  
Author(s):  
W. Lieberthal ◽  
M. L. Vasilevsky ◽  
C. R. Valeri ◽  
N. G. Levinsky
Keyword(s):  
Sodium Excretion ◽  
Rat Kidney ◽  
Urine Osmolality ◽  
Sodium Reabsorption ◽  
Urinary Osmolality ◽  
Hemodynamic Characteristics ◽  
Urinary Concentrating Ability ◽  
Tubular Morphology ◽  
Isolated Kidneys

Interactions between antidiuretic hormone (ADH) and renal prostaglandins in the regulation of sodium reabsorption and urinary concentrating ability were studied in isolated erythrocyte-perfused rat kidneys (IEPK). In this model, hemodynamic characteristics are comparable to those found in vivo, and tubular morphology is preserved throughout the period of perfusion. [Deamino]-D-arginine vasopressin (dDAVP) markedly reduced fractional sodium excretion (FE Na) in the IEPK from 3.5 +/- 0.6 to 0.45 +/- 0.14%. After indomethacin, FE Na fell still further to 0.08 +/- 0.02%. In the absence of dDAVP indomethacin had no effect on sodium excretion; FE Na was 2.4 +/- 0.6% in control and 2.0 +/- 0.4% in indomethacin-treated groups. dDAVP increased urine osmolality in the IEPK to 741 +/- 26 mosmol/kg. When prostaglandin synthesis was blocked with indomethacin, urinary osmolality increased further to 1,180 +/- 94 mosmol/kg. In isolated kidneys perfused without erythrocytes (IPK), dDAVP decreased FENa from 14.5 +/- 1.8% to 9.6 +/- 1.2%; addition of indomethacin had no further effect. dDAVP increased urine osmolality only modestly to 350 +/- 12 mosmol/kg in the IPK and indomethacin did not increase concentrating ability further (342 +/- 7 mosmol/kg). Thus the IEPK (unlike the IPK) can excrete a markedly hypertonic urine in response to ADH. ADH also enhances tubular reabsorption of sodium in the IEPK. Prostaglandins inhibit both these actions of ADH but do not directly affect sodium excretion in the absence of the hormone.

Effect of potassium concentration and ouabain on the renal adaptation to potassium depletion in isolated perfused rat kidney

1986 ◽  
Vol 64 (11) ◽  
pp. 1427-1433 ◽  
Author(s):  
Daniel B. Ornt
Keyword(s):  
Sodium Excretion ◽  
Rat Kidney ◽  
Control Diet ◽  
Kidney Tissue ◽  
Renal Tissue ◽  
Renal Adaptation ◽  
Low K ◽  
K Depletion ◽  
Isolated Kidneys

Renal adaptation for potassium (K) conservation has been demonstrated in isolated perfused kidneys from rats within 3 days of K depletion and appears to be independent of aldosterone and sodium excretion. This study was designed to investigate whether the renal adaptation for K conservation is independent of ambient [K] and renal tissue levels of K and whether ouabain may have effects on K excretion, which are in constrast to the effects on K excretion in normal animals, in the first study, rats K depleted for 3 days received 2500 μequiv. KCl intraperitoneally, while other K-depleted rats and a group of control diet animals received intraperitoneal H2O alone to determine whether simple restoration of K deficits would reverse the renal adaptation for K conservation. Intraperitoneal KCl increased plasma [K] and kidney tissue K significantly within 3 h in the K-repleted group compared with the K-depleted rats. Isolated kidneys were perfused from the three groups of rats 3 h after intraperitoneal injection. Despite K repletion in vivo, perfused kidneys from the K-repleted group still had significantly decreased K excretion (1.28 ± 0.085 μequiv./min) compared with controls (2.05 ± 0.291 μequiv./min), and K excretion was still not different from the K-depleted group (0.57 ± 0.134 μequiv./min). However, fractional K excretion by the kidneys from K-repleted rats was increased above K-depleted kidneys (0.48 ± 0.051 vs. 0.18 ± 0.034, p < 0.01). Despite the increased renal tissue K in K-repleted kidneys at the start of perfusion (285 ± 5.1 vs. 257 ± 5.4 μequiv./g), by the end of the perfusion tissue K in perfused kidneys was identical in all three groups. In the second study, isolated kidneys were perfused from 3-day K-depleted or control rats with either 2 or 6 mM [K] in the perfusate. Isolated kidneys adapted to 3 days of K depletion excreted less K at both 2 and 6 mM [K] compared with controls at the same ambient [K]. The linear relationship of K excretion to perfusate [K] was significantly different in controls compared with low K adapted kidneys (p < 0.001). Finally, when 10−4 M ouabain was added after 60 min of perfusion in kidneys from control diet rats, there was a sodium diuresis and fractional K excretion decreased significantly (0.55 ± 0.043 to 0.32 ± 0.044, p < 0.01). However, in low K adapted kidneys, ouabain had no effect on fractional K excretion (0.020 ± 0.051 to 0.18 ± 0.038) despite a similar increase in sodium excretion. Perfusions of kidneys from 3-day K-depleted rats at 4 × 10−3 M ouabain gave similar results, showing no change in fractional K excretion. Low K adaptation to K depletion developed within 3 days and was not totally abolished by acute K repletion. Maneuvers that favored either a decrease in renal tissue K or an increase in tissue K did not reverse low K adaptation, although renal tissue K levels did alter the rate of K excretion in both controls and K-depleted kidneys. Therefore, a reduction in tissue K was clearly not the sole mediator of renal K conservation. Finally, the markedly different response of low K adapted kidneys to ouabain compared with controls strongly suggests a mechanism for K reabsorption that developed within 3 days of K depletion and is ouabain sensitive.

Dopamine production by the isolated perfused rat kidney

1984 ◽  
Vol 62 (3) ◽  
pp. 272-276 ◽  
Author(s):  
Andrew D. Baines ◽  
Rosa Drangova
Keyword(s):  
Sodium Excretion ◽  
Filtration Rate ◽  
Rat Kidney ◽  
Kidney Weight ◽  
Perfused Rat Kidney ◽  
Wet Weight ◽  
Collection Period ◽  
Renal Vascular ◽  
Isolated Kidneys

We used isolated perfused rat kidneys to examine dopamine (DA) production and its relation to renal function. Both innervated and chronically surgically denervated kidneys perfused with a solution containing neither albumin nor tyrosine, excreted 0.2 ± 0.1 ng DA∙min−1∙g wet weight−1 during the 10-min collection period between 30 and 40 min after starting perfusion. When perfused with 6.7% albumin, without tyrosine, innervated kidneys excreted 1.0 ± 0.06 ng DA∙min−1∙g−1 and denervated kidneys excreted 1.0 ± 0.07 DA∙min−1∙g−1. When 0.03 mM tyrosine was included in the albumin perfusate, innervated kidneys excreted 1.2 ± 0.1 ng DA∙min−1∙g−1 (p < 0.1). Under these conditions DA excretion continued for at least 100 min at which time it was 0.6 ng∙min−1∙g−1 and 86 ng/g kidney weight had been excreted. Denervated kidneys perfused with albumin + tyrosine excreted 0.9 ± 0.13 ng DA∙min−1∙g−1. Renal stores of free DA, conjugated DA, and dihydroxyphenylalanine (DOPA) could have provided at the most 30 ng/g of DA. Carbidopa inhibited DA excretion completely. DA excretion did not correlate with renal vascular resistance, inulin clearance, or fractional sodium excretion. In summary, nonneural tissue in isolated perfused kidneys produced DA at the same rate as denervated kidneys in vivo. Less than one-third of the DA produced by isolated kidneys could have come from intrarenal stores of DOPA, free DA, and conjugated DA; the rest was synthesized from unknown precursors. Circulating DOPA and tyrosine were not the DA precursors, but albumin was required to obtain production rates similar to those in vivo. Nonneuronal DA production did not influence renal hemodynamics, glomerular filtration rate (GFR), or sodium excretion.

Role of endothelin receptor subtypes in the in vivo regulation of renal function

1995 ◽  
Vol 268 (3) ◽  
pp. F455-F460 ◽  
Author(s):  
A. L. Clavell ◽  
A. J. Stingo ◽  
K. B. Margulies ◽  
R. R. Brandt ◽  
J. C. Burnett
Keyword(s):  
Sodium Excretion ◽  
Urine Osmolality ◽  
Receptor Activation ◽  
Receptor Subtypes ◽  
Low Doses ◽  
Renal Vasoconstriction ◽  
Etb Receptor ◽  
Diuretic Response

Endothelin (ET) is a potent vasoconstrictor peptide of endothelial origin, which at low doses results in renal vasoconstriction and diuresis with variable actions on sodium excretion. The current study conducted in four groups of anesthetized dogs was designed to define the role of the ETA and ETB receptor subtypes in the renal actions of low-dose exogenous ET. Group 1 (n = 4) animals served as time controls. In group 2 (n = 6) a systemic ET-1 (5 ng.kg-1.min-1) infusion mediated renal vasoconstriction, antinatriuresis with increases in proximal fractional reabsorption of sodium, and diuresis with a decrease in urine osmolality. In group 3 (n = 6) intrarenal BQ-123 (4 micrograms.kg-1.min-1), a selective ETA antagonist, abolished the systemic ET-1-mediated changes in renal hemodynamics and unmasked a natriuretic action at the level of the proximal tubule. In contrast, the diuretic response of ET was not altered by BQ-123. In group 4 (n = 6) intrarenal sarafotoxin 6-c, a selective ETB receptor agonist, resulted in a diuretic response without a change in sodium excretion. These studies suggest that the ETA receptor contributes to the renal vasoconstriction, whereas the ETB receptor is largely responsible for the diuretic response during exogenous ET. This study also suggests that at low doses ET is natriuretic in vivo by decreasing proximal tubular reabsorption of sodium independent of ETA or ETB receptor activation.

Localization and regulation of the rat renal Na(+)-K(+)-2Cl- cotransporter, BSC-1

1996 ◽  
Vol 271 (3) ◽  
pp. F619-F628 ◽  
Author(s):  
C. A. Ecelbarger ◽  
J. Terris ◽  
J. R. Hoyer ◽  
S. Nielsen ◽  
J. B. Wade ◽  
...  
Keyword(s):  
Rat Kidney ◽  
Rat Colon ◽  
Thick Ascending Limb ◽  
Outer Medulla ◽  
Water Excretion ◽  
Saline Loading ◽  
Cloned Cdna ◽  
Urinary Concentrating Ability

To investigate the role of the thick ascending limb (TAL) Na(+)-K(+)-2Cl- cotransporter in regulation of water excretion, we have prepared a peptide-derived polyclonal antibody based on the cloned cDNA sequence of the rat type 1 bumetanide-sensitive cotransporter, BSC-1 (also termed "NKCC-2"). Immunoblots revealed a single broad 161-kDa band in membrane fractions of rat renal outer medulla and cortex but not from rat colon or parotid gland. A similar protein was labeled in mouse kidney. Immunoperoxidase immunohistochemistry in rat kidney revealed labeling restricted to the medullary and cortical TAL segments. Because long-term regulation of urinary concentrating ability may depend on regulation of Na(+)-K(+)-2Cl- cotransporter abundance, we used immunoblotting to evaluate the effects of several in vivo factors on expression levels of BSC-1 protein in rat kidney outer medulla. Chronic oral saline loading with 0.16 M NaCl markedly increased BSC-1 abundance. However, long-term vasopressin infusion or thirsting of rats did not affect BSC-1 abundance. Chronic furosemide infusion caused a 9-kDa upward shift in apparent molecular mass and an apparent increase in expression level. These results support the previous identification of BSC-1 as the TAL Na(+)-K(+)-2Cl- transporter and demonstrate that the expression of this transporter is regulated.

Renal localization and actions of adrenomedullin: a natriuretic peptide

1995 ◽  
Vol 268 (4) ◽  
pp. F657-F663 ◽  
Author(s):  
M. Jougasaki ◽  
C. M. Wei ◽  
L. L. Aarhus ◽  
D. M. Heublein ◽  
S. M. Sandberg ◽  
...  
Keyword(s):  
Natriuretic Peptide ◽  
Sodium Excretion ◽  
Collecting Duct ◽  
Plasma Concentrations ◽  
In Vivo Studies ◽  
Sodium Reabsorption ◽  
Contralateral Kidney ◽  
Arterial Blood ◽  
Group I

Adrenomedullin (ADM) is a newly described 52-amino acid peptide originally isolated from extracts of human pheochromocytoma and, more recently, detected in human plasma. Based on the report that ADM mRNA and immunoreactivity are present in the kidney, the current study was designed to determine the renal distribution of ADM by immunohistochemistry and the renal biological actions of ADM. In the immunohistochemical studies, the present investigation demonstrated the localization of ADM in glomeruli, cortical distal tubules, and medullary collecting duct cells of the normal canine kidney. In the in vivo studies, ADM was administered (0.25 ng.kg-1.min-1 in group I and 1, 5, and 25 ng.kg-1.min-1 in group II) intrarenally in normal mongrel dogs with the contralateral kidney receiving only saline vehicle. Intrarenal infusion of ADM resulted in a marked diuretic and natriuretic response, whereas the contralateral kidney showed no renal effects. These significant natriuresis and diuresis in the ADM kidney were associated with increases in glomerular filtration rate and fractional sodium excretion and with a decrease in distal tubular sodium reabsorption. Intrarenal infusion of ADM also caused an increase in mean arterial blood pressure and a decrease in heart rate. Plasma concentrations of atrial natriuretic peptide, renin activity, aldosterone, and guanosine 3',5'-cyclic monophosphate were not changed during the infusion of ADM. The current study demonstrates that ADM is present in renal glomerular and tubular cells and is a potent natriuretic peptide that may play an important role in the regulation of sodium excretion.

scholarly journals ANP-mediated inhibition of distal nephron fractional sodium reabsorption in wild-type and mice overexpressing natriuretic peptide receptor

2010 ◽  
Vol 298 (1) ◽  
pp. F103-F108 ◽  
Author(s):  
Di Zhao ◽  
Kailash N. Pandey ◽  
L. Gabriel Navar
Keyword(s):  
Natriuretic Peptide ◽  
Sodium Excretion ◽  
Urinary Sodium Excretion ◽  
Sodium Reabsorption ◽  
Natriuretic Peptide Receptor ◽  
Distal Nephron ◽  
Peptide Receptor ◽  
Natriuretic Peptide Receptor A ◽  
Npr1 Gene

Atrial natriuretic peptide (ANP) elicits natriuresis; however, the relative contributions of proximal and distal nephron segments to the overall ANP-induced natriuresis have remained uncertain. This study was performed to characterize the effects of ANP on distal nephron sodium reabsorption determined after blockade of the two major distal nephron sodium transporters with amiloride (5 μg/g body wt) plus bendroflumethiazide (12 μg/g body wt) in male anesthetized C57/BL6 and natriuretic peptide receptor-A gene (Npr1) targeted four-copy mice. The lower dose of ANP (0.1 ng·g body wt−1·min−1, n = 6) increased distal sodium delivery (DSD, 2.4 ± 0.4 vs. 1.6 ± 0.2 μeq/min, P < 0.05) but did not change fractional reabsorption of DSD compared with control (86.3 ± 2.0 vs. 83.9 ± 3.6%, P > 0.05), thus limiting the magnitude of the natriuresis. In contrast, the higher dose (0.2 ng·g body wt−1·min−1, n = 6) increased DSD (2.8 ± 0.3 μeq/min, P < 0.01) and also decreased fractional reabsorption of DSD (67.4 ± 4.5%, P < 0.01), which markedly augmented the natriuresis. In Npr1 gene-duplicated four-copy mice ( n = 6), the lower dose of ANP increased urinary sodium excretion (0.6 ± 0.1 vs. 0.3 ± 0.1 μeq/min, P < 0.05) and decreased fractional reabsorption of DSD compared with control (72.2 ± 3.4%, P < 0.05) at similar mean arterial pressures (91 ± 6 vs. 92 ± 3 mmHg, P > 0.05). These results provide in vivo evidence that ANP-mediated increases in DSD alone exert modest effects on sodium excretion and that inhibition of fractional reabsorption of distal sodium delivery is requisite for the augmented natriuresis in response to the higher dose of ANP or in Npr1 gene-duplicated mice.

Sodium excretion during elevation of renal venous pressure: modulation by dDAVP

1989 ◽  
Vol 256 (5) ◽  
pp. F776-F779
Author(s):  
J. D. Firth ◽  
A. E. Raine ◽  
J. G. Ledingham
Keyword(s):  
Sodium Excretion ◽  
Rat Kidney ◽  
Linear Regression Analysis ◽  
Venous Pressure ◽  
Perfusate Flow ◽  
Data Points ◽  
V2 Receptor ◽  
Pressure Modulation ◽  
Perfusate Flow Rate

Studies were performed to determine the effects of elevation of renal venous pressure on sodium excretion by the isolated perfused rat kidney in the presence and absence of a specific V2-receptor agonist, 1-des-amino-8-D-arginine vasopressin (dDAVP), at a concentration (1 ng/ml) expected to have maximal antidiuretic activity but minor vasopressor action. In either the presence or absence of dDAVP, increments in venous pressure led to falls in perfusate flow rate and glomerular filtration rate, which became significant at an imposed pressure greater than or equal to 18.75 mmHg. In the absence of dDAVP, absolute sodium excretion fell as venous pressure increased, and there was a negative correlation between fractional sodium excretion (FENa) and renal venous pressure (RVP) within each experiment and when all data points were combined: FENa = 3.46-0.072RVP (r = -0.608, P less than 0.01). In contrast, in the presence of dDAVP, absolute sodium excretion was unchanged, and in four of five experiments FENa rose as venous pressure increased (in one it remained unchanged). Linear regression analysis of all data points showed a positive correlation between FENa and RVP: FENa = 1.27 + 0.127RVP (r = 0.392, P less than 0.05). The slopes of the two regression lines were significantly different (P less than 0.001). It is postulated that this effect of dDAVP may be mediated via changes in the distal tubular pressure response to elevation of RVP. Such an effect of vasopressin could explain the observation that the response to renal vein constriction in vivo is dependent on volume status.

scholarly journals Effects of pH and medullary blood flow on oxygen transport and sodium reabsorption in the rat outer medulla

2010 ◽  
Vol 298 (6) ◽  
pp. F1369-F1383 ◽  
Author(s):  
Jing Chen ◽  
Aurélie Edwards ◽  
Anita T. Layton
Keyword(s):  
Blood Flow ◽  
Rat Kidney ◽  
Sodium Reabsorption ◽  
Vascular Bundles ◽  
Outer Medulla ◽  
Medullary Blood Flow ◽  
Blood Ph ◽  
Effects Of Ph ◽  
Tubular Flow

We used a mathematical model of O2 transport and the urine concentrating mechanism of the outer medulla of the rat kidney to study the effects of blood pH and medullary blood flow on O2 availability and Na+ reabsorption. The model predicts that in vivo paracellular Na+ fluxes across medullary thick ascending limbs (mTALs) are small relative to transcellular Na+ fluxes and that paracellular fluxes favor Na+ reabsorption from the lumen along most of the mTAL segments. In addition, model results suggest that blood pH has a significant impact on O2 transport and Na+ reabsorption owing to the Bohr effect, according to which a lower pH reduces the binding affinity of hemoglobin for O2. Thus our model predicts that the presumed greater acidity of blood in the interbundle regions, where mTALs are located, relative to that in the vascular bundles, facilitates the delivery of O2 to support the high metabolic requirements of the mTALs and raises the concentrating capability of the outer medulla. Model results also suggest that increases in vascular and tubular flow rates result in disproportional, smaller increases in active O2 consumption and mTAL active Na+ transport, despite the higher delivery of O2 and Na+. That is, at a sufficiently high medullary O2 supply, O2 demand in the outer medulla does not adjust precisely to changes in O2 delivery.

scholarly journals Long-term aldosterone treatment induces decreased apical but increased basolateral expression of AQP2 in CCD of rat kidney

2007 ◽  
Vol 293 (1) ◽  
pp. F87-F99 ◽  
Author(s):  
Sophie de Seigneux ◽  
Jakob Nielsen ◽  
Emma T. B. Olesen ◽  
Henrik Dimke ◽  
Tae-Hwan Kwon ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Urine Volume ◽  
Urine Osmolality ◽  
Sodium Reabsorption ◽  
Urinary Concentration ◽  
High Dose ◽  
Free Access ◽  
Cortical Collecting Duct ◽  
Water Metabolism

The purpose of the present studies was to determine the effects of high-dose aldosterone and dDAVP treatment on renal aquaporin-2 (AQP2) regulation and urinary concentration. Rats were treated for 6 days with either vehicle (CON; n = 8), dDAVP (0.5 ng/h, dDAVP, n = 10), aldosterone (Aldo, 150 μg/day, n = 10) or combined dDAVP and aldosterone treatment (dDAVP+Aldo, n = 10) and had free access to water with a fixed food intake. Aldosterone treatment induced hypokalemia, decreased urine osmolality, and increased the urine volume and water intake in ALDO compared with CON and dDAVP+Aldo compared with dDAVP. Immunohistochemistry and semiquantitative laser confocal microscopy revealed a distinct increase in basolateral domain AQP2 labeling in cortical collecting duct (CCD) principal cells and a reduction in apical domain labeling in Aldo compared with CON rats. Given the presence of hypokalemia in aldosterone-treated rats, we studied dietary-induced hypokalemia in rats, which also reduced apical AQP2 expression in the CCD but did not induce any increase in basolateral AQP2 expression in the CCD as observed with aldosterone treatment. The aldosterone-induced basolateral AQP2 expression in the CCD was thus independent of hypokalemia but was dependent on the presence of sodium and aldosterone. This redistribution was clearly blocked by mineralocorticoid receptor blockade. The increased basolateral expression of AQP2 induced by aldosterone may play a significant role in water metabolism in conditions with increased sodium reabsorption in the CCD.

Pressure-dependent action of angiotensin II on glomerular filtration in the isolated rat kidney

1982 ◽  
Vol 60 (10) ◽  
pp. 1311-1314 ◽  
Author(s):  
Thomas H. Steele ◽  
Jeanne H. Gottstein ◽  
Laura Challoner-Hue
Keyword(s):  
Angiotensin Ii ◽  
Glomerular Filtration ◽  
Sodium Excretion ◽  
Rat Kidney ◽  
Sodium Concentration ◽  
Renal Perfusion ◽  
Sodium Reabsorption ◽  
Urine Sodium ◽  
Isolated Rat Kidney ◽  
Isolated Rat

We examined the action of angiotensin II (AII) on isolated rat kidney perfused with a recirculating cell-free solution at either 12 pKa (90 mmHg) or 17 kPa (128 mmHg). The renal perfusion pressure was maintained constant while sufficient All was added to increase the renal vascular resistance by 50%. In the low-pressure kidneys, AII increased the glomerular filtration rate (GFR) by 155%, increased sodium reabsorption by 157%, and decreased the urine sodium concentration by 34% without affecting sodium excretion. In the high-pressure kidneys, GFR initially was significantly greater but was not affected by AII. In these experiments, AII had no effect on sodium reabsorption or excretion and decreased the urine sodium concentration by 7%. The data suggest that AII could be involved in autoregulation of the GFR without producing large changes in sodium excretion.

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