Differentiation of Na+-K+ pump in rat proximal tubule is modulated by Na+-H+ exchanger

1988 ◽  
Vol 255 (3) ◽  
pp. F552-F557 ◽  
Author(s):  
Y. Fukuda ◽  
A. Aperia
Keyword(s):  
Atpase Activity ◽  
Rat Kidney ◽  
Thick Ascending Limb ◽  
Adult Rats ◽  
Entry Pathway ◽  
Medullary Thick Ascending Limb ◽  
Weanling Rats ◽  
Rat Proximal Tubule ◽  
Exchange Activity

This study examines the effect of in vivo modulation of Na+-H+ exchange activity on the development of Na+-K+-ATPase in rat kidney proximal convoluted tubule (PCT) segments. To stimulate Na+-H+ exchanger (major entry pathway for Na in PCT), weanling rats were fed NH4Cl for 4 days to induce metabolic acidosis (MA). In vehicle (Vh)-fed rats PCT Na+-K+-ATPase activity (pmol Pi.mm tubule-1.h-1 +/- SE) increased from 481 +/- 78 at 16 days to 1,122 +/- 119 at 20 days. In 20-day-old chronic MA rats, PCT Na+-K+-ATPase activity was 1,717 +/- 109, i.e., significantly higher (P less than 0.01) relative to controls. Chronic MA had no effect on PCT Mg ATPase activity and on Na+-K+-ATPase in the medullary thick ascending limb (MTAL). To inhibit the Na+-H+ exchanger, weanling rats received amiloride (30 micrograms.100 g body wt-1.day-1) via osmotic minipump for 4 days. In Vh-treated rats PCT Na+-K+-ATPase increased from 481 +/- 78 at 16 days to 1,428 +/- 81 at 20 days. In rats given chronic amiloride, PCT Na+-K+-ATPase was significantly lower (858 +/- 75) at 20 days relative to controls but PCT Mg ATPase and MTAL Na+-K+-ATPase activity was the same as in controls. Chronic MA and amiloride had no significant effect on PCT Na+-K+-ATPase activity in adult rats. Acute MA and acute amiloride injection had no significant effect on PCT Na+-K+-ATPase in weanling rats.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Cloning, renal distribution, and regulation of the rat Na+- HCO 3 − cotransporter

1998 ◽  
Vol 274 (6) ◽  
pp. F1119-F1126 ◽  
Author(s):  
Charles E. Burnham ◽  
Michael Flagella ◽  
Zhaohui Wang ◽  
Hassane Amlal ◽  
Gary E. Shull ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Rat Kidney ◽  
Human Kidney ◽  
Cloning And Expression ◽  
Thick Ascending Limb ◽  
Mrna Levels ◽  
Reading Frame ◽  
Medullary Thick Ascending Limb ◽  
Nephron Segment

We recently reported the cloning and expression of a human kidney Na+-[Formula: see text]cotransporter (NBC-1) (C. E. Burnham, H. Amlal, Z. Wang, G. E. Shull, and M. Soleimani. J. Biol. Chem. 272: 19111–19114, 1997). To expedite in vivo experimentation, we now report the cDNA sequence of rat kidney NBC-1. In addition, we describe both the organ and nephron segment distributions and the regulation of NBC-1 mRNA under three models of pH stress: chloride-depletion alkalosis (CDA), metabolic acidosis, and bicarbonate loading. Rat NBC-1 cDNA encodes an open reading frame of 1,035 amino acids, with 96 and 87% identity to human and salamander NBC-1, respectively. Rat NBC-1 mRNA is expressed at high levels in kidney and brain, with lower levels in colon, stomach, and heart. None appears in liver. In the kidney, NBC-1 is expressed mainly in the proximal tubule, with traces found in medullary thick ascending limb and papilla. [Formula: see text] loading decreased NBC-1 mRNA levels, which were unchanged either by metabolic acidosis or by CDA.

Adrenalectomy reduces alpha 1 and not beta 1 Na(+)-K(+)-ATPase mRNA expression in rat distal nephron

1992 ◽  
Vol 263 (4) ◽  
pp. C810-C817 ◽  
Author(s):  
N. Farman ◽  
N. Coutry ◽  
N. Logvinenko ◽  
M. Blot-Chabaud ◽  
R. Bourbouze ◽  
...  
Keyword(s):  
Rat Kidney ◽  
Unit Surface Area ◽  
Thick Ascending Limb ◽  
Cell Type ◽  
Adult Rats ◽  
Medullary Thick Ascending Limb ◽  
Normal Rat ◽  
Beta 2

The abundance of mRNA of alpha 1-, alpha 2-, alpha 3-, beta 1-, and beta 2-isoforms of Na(+)-K(+)-ATPase was examined in several renal structures of normal and adrenalectomized (ADX) rats. In situ hybridization with 35S-labeled cRNA probes was performed on kidney sections from adult rats. The number of silver grains per unit surface area was quantified over cells of the glomerulus, proximal convoluted tubules (PCT), early distal tubules (EDT), and cortical collecting ducts (CCD). In normal rat kidney, alpha 1- and beta 1-mRNA was detected in PCT, EDT, and CCD, with the following range of magnitude: EDT > CCD > PCT > glomerulus. The amount of alpha 1- and beta 1-mRNA was equivalent. A large abundance of these two mRNA species was also found in the medullary thick ascending limb of the loop of Henle. Expression of alpha 2, alpha 3, and beta 2 was very low and evenly distributed over any cell type. In ADX, a significant decrease in alpha 1-mRNA (30%) was observed in EDT and CCD, with no change in PCT. beta 1-mRNA abundance was unaffected by adrenalectomy. These results indicate that 1) in the rat kidney alpha 1- and beta 1-mRNA are coexpressed at a similar level that varies along the renal tubule according to the cell type, 2) minute expression of alpha 2-, alpha 3-, and beta 2-mRNA is present in the kidney, and 3) corticosteroid depletion reduces the expression of alpha 1- and not beta 1-mRNA in the corticosteroid-sensitive tubular cells.

In vitro stimulation of Na-K-ATPase in rat thick ascending limb by dexamethasone

1986 ◽  
Vol 251 (5) ◽  
pp. F851-F857 ◽  
Author(s):  
A. Doucet ◽  
A. Hus-Citharel ◽  
F. Morel
Keyword(s):  
Atpase Activity ◽  
Sodium Reabsorption ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Short Term ◽  
Medullary Thick Ascending Limb ◽  
Dose Dependent ◽  
Stimulation Of

Dexamethasone has been reported to stimulate Na-K-ATPase activity in the medullary thick ascending limb of adrenalectomized animals within a few hours. The present study was aimed at characterizing the mechanism of this action by investigating the stimulatory effect of the hormone in vitro. Dexamethasone (10(-8) M) added in vitro to segments of the medullary thick ascending limb of Henle's loop, which were microdissected from adrenalectomized rats, restored in a dose-dependent manner the depressed Na-K-ATPase activity within one h of incubation. This stimulation of Na-K-ATPase was inhibited by cycloheximide and actinomycin D. Dexamethasone also stimulated the component of oxidative metabolism coupled to sodium transport. These results, which confirm previous in vivo observations, demonstrate that dexamethasone-induced stimulation of Na-K-ATPase is a direct tubular action of the hormone mediated by protein synthesis. They suggest that this short-term effect of dexamethasone corresponds to the stimulation of sodium reabsorption by the dilution segment.

scholarly journals High sodium intake increases HCO3− absorption in medullary thick ascending limb through adaptations in basolateral and apical Na+/H+ exchangers

2011 ◽  
Vol 301 (2) ◽  
pp. F334-F343 ◽  
Author(s):  
David W. Good ◽  
Thampi George ◽  
Bruns A. Watts
Keyword(s):  
Absorptive Capacity ◽  
Sodium Intake ◽  
Thick Ascending Limb ◽  
Acid Base Balance ◽  
High Sodium ◽  
High Sodium Intake ◽  
Medullary Thick Ascending Limb ◽  
Nhe1 Activity ◽  
Exchange Activity

A high sodium intake increases the capacity of the medullary thick ascending limb (MTAL) to absorb HCO3−. Here, we examined the role of the apical NHE3 and basolateral NHE1 Na+/H+ exchangers in this adaptation. MTALs from rats drinking H2O or 0.28 M NaCl for 5–7 days were perfused in vitro. High sodium intake increased HCO3− absorption rate by 60%. The increased HCO3− absorptive capacity was mediated by an increase in apical NHE3 activity. Inhibiting basolateral NHE1 with bath amiloride eliminated 60% of the adaptive increase in HCO3− absorption. Thus the majority of the increase in NHE3 activity was dependent on NHE1. A high sodium intake increased basolateral Na+/H+ exchange activity by 89% in association with an increase in NHE1 expression. High sodium intake increased apical Na+/H+ exchange activity by 30% under conditions in which basolateral Na+/H+ exchange was inhibited but did not change NHE3 abundance. These results suggest that high sodium intake increases HCO3− absorptive capacity in the MTAL through 1) an adaptive increase in basolateral NHE1 activity that results secondarily in an increase in apical NHE3 activity; and 2) an adaptive increase in NHE3 activity, independent of NHE1 activity. These studies support a role for NHE1 in the long-term regulation of renal tubule function and suggest that the regulatory interaction whereby NHE1 enhances the activity of NHE3 in the MTAL plays a role in the chronic regulation of HCO3− absorption. The adaptive increases in Na+/H+ exchange activity and HCO3− absorption in the MTAL may play a role in enabling the kidneys to regulate acid-base balance during changes in sodium and volume balance.

Na-K-ATPase activity along the rabbit, rat, and mouse nephron

1979 ◽  
Vol 237 (2) ◽  
pp. F114-F120 ◽  
Author(s):  
A. I. Katz ◽  
A. Doucet ◽  
F. Morel
Keyword(s):  
Atpase Activity ◽  
Thick Ascending Limb ◽  
Sensitivity Limit ◽  
Henle's Loop ◽  
Collecting Tubule ◽  
Pars Recta ◽  
Hydrolysis Of ◽  
Total Enzyme

Na-K-ATPase activity along the rabbit, rat, and mouse nephron was determined with a micromethod that measures directly labeled phosphate released by the hydrolysis of [gamma-32P]ATP. Na-K-ATPase activity was highest in the rat, intermediate in the mouse, and lowest in the rabbit nephron. With the exception of rabbit cortical thick ascending limb, the enzyme profile was similar in the three species: Na-K-ATPase activity per millimeter tubule length was highest in the distal convoluted tubule and thick ascending limb of Henle's loop, intermediate in the proximal convoluted tubule, and lowest in the pars recta and collecting tubule. The enzyme was present in the thin limbs of Henle's loop, but its activity was very low and measurements were close to the sensitivity limit of the method. Both the absolute activity and the fraction of the total enzyme represented by Na-K-ATPase were severalfold higher than in kidney homogenates. Finally, the Na-K-ATPase activity measured in certain segments of the rat and rabbit nephron in this study seems sufficient to account in theory for the active component of the net sodium transport found in the corresponding region of the nephron with either in vivo or in vitro single tubule microperfusion techniques.

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.

scholarly journals Angiotensin II inhibits NaCl absorption in the rat medullary thick ascending limb

2004 ◽  
Vol 287 (3) ◽  
pp. F404-F410 ◽  
Author(s):  
Nicolas Lerolle ◽  
Soline Bourgeois ◽  
Françoise Leviel ◽  
Gaëtan Lebrun ◽  
Michel Paillard ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Plasma Membranes ◽  
Inhibitory Effect ◽  
Thick Ascending Limb ◽  
Sprague Dawley ◽  
Experimental Conditions ◽  
Nacl Absorption ◽  
Medullary Thick Ascending Limb

NaCl reabsorption in the medullary thick ascending limb of Henle (MTALH) contributes to NaCl balance and is also responsible for the creation of medullary interstitial hypertonicity. Despite the presence of angiotensin II subtype 1 (AT1) receptors in both the luminal and the basolateral plasma membranes of MTALH cells, no information is available on the effect of angiotensin II on NaCl reabsorption in MTALH and, furthermore, on angiotensin II-dependent medullary interstitial osmolality. MTALHs from male Sprague-Dawley rats were isolated and microperfused in vitro; transepithelial net chloride absorption ( JCl) as well as transepithelial voltage ( Vte) were measured. Luminal or peritubular 10−11 and 10−10 M angiotensin II had no effect on JCl or Vte. However, 10−8 M luminal or peritubular angiotensin II reversibly decreased both JCl and Vte. The effect of both luminal and peritubular angiotensin II was prevented by the presence of losartan (10−6 M). By contrast, PD-23319, an AT2-receptor antagonist, did not alter the inhibitory effect of 10−8 M angiotensin II. Finally, no additive effect of luminal and peritubular angiotensin II was observed. We conclude that both luminal and peritubular angiotensin II inhibit NaCl absorption in the MTALH via AT1 receptors. Because of intrarenal angiotensin II synthesis, angiotensin II concentration in medullary tubular and interstitial fluids may be similar in vivo to the concentration that displays an inhibitory effect on NaCl reabsorption under the present experimental conditions.

Interactions of external and internal K+ with K(+)-HCO3- cotransporter of rat medullary thick ascending limb

1996 ◽  
Vol 271 (1) ◽  
pp. C218-C225 ◽  
Author(s):  
A. Blanchard ◽  
F. leviel ◽  
M. Bichara ◽  
R. A. Podevin ◽  
M. Paillard
Keyword(s):  
Maximum Velocity ◽  
Hill Coefficient ◽  
Kinetic Properties ◽  
Thick Ascending Limb ◽  
Medullary Thick Ascending Limb ◽  
Sigmoidal Curve ◽  
K Concentration ◽  
Physiological Variations ◽  
Allosteric Activator

We studied [K+]i and [K+]o, where subscripts i and o refer to intracellular and extracellular, respectively, concentration dependency of the kinetic properties of the electroneutral K(+)-HCO3-cotransport, using suspensions of rat medullary thick ascending limb (mTAL). With the use of nigericin and monensin, [K+]i was clamped at various values, while maintaining [Na+]i = [Na+]o = 37 mM, [HCO3-]i = [HCO3-]o = 23 mM, and pHi = pHo = 7.4. As indicated by 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein HCO3(-)-dependent rates of change in pHi, at constant [K+]i, increasing the magnitude of the outward K+ gradient by varying [K+]o saturated HCO3-efflux with a Michaelis-Menten curve (apparent Michaelis constant for [K+]o = 2 mM, Hill coefficient = 1). On the other hand, increasing [K+]i from 30 to 140 mM, while either [K+]o or the magnitude of the K+ concentration gradient was fixed, saturated HCO3- efflux with a sigmoidal curve and yielded a Hill coefficient of 3.4 and 50% of maximum velocity at 70 mM [K+]i. These results indicate that [K+]i, independent of its role as a transportable substrate for the cotransport with HCO3-, has a role as an allosteric activator of the K(+)-HCO3- cotransporter. Such an allosteric modulation may contribute to the maintenance of net HCO3- absorption despite large in vivo physiological variations of K+ concentration in the medullary interstitium.

Regional and segmental localization of AE2 anion exchanger mRNA and protein in rat kidney

1995 ◽  
Vol 269 (4) ◽  
pp. F461-F468 ◽  
Author(s):  
F. C. Brosius ◽  
K. Nguyen ◽  
A. K. Stuart-Tilley ◽  
C. Haller ◽  
J. P. Briggs ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Chloride Concentration ◽  
Transepithelial Transport ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Base Exchange ◽  
Medullary Thick Ascending Limb ◽  
Nephron Segment ◽  
Medullary Collecting Duct

Chloride/base exchange activity has been detected in every mammalian nephron segment in which it has been sought. However, in contrast to the Cl-/HCO3- exchanger AE1 in type A intercalated cells, localization of AE2 within the kidney has not been reported. We therefore studied AE2 expression in rat kidney. AE2 mRNA was present in cortex, outer medulla, and inner medulla. Semiquantitative polymerase chain reaction of cDNA from microdissected tubules revealed AE2 cDNA levels as follows [copies of cDNA derived per mm tubule (+/- SE)]: proximal convoluted tubule, 688 +/- 161; proximal straight tubule, 652 +/- 189; medullary thick ascending limb, 1,378 +/- 226; cortical thick ascending limb, 741 +/- 24; cortical collecting duct, 909 +/- 71; and outer medullary collecting duct, 579 +/- 132. AE2 cDNA was also amplified in thin limbs and in inner medullary collecting duct. AE2 polypeptide was detected in all kidney regions. AE2 mRNA and protein were also detected in several renal cell lines. The data are compatible with the postulated roles of AE2 in maintenance of intracellular pH and chloride concentration and with its possible participation in transepithelial transport.

scholarly journals Water and solute permeabilities of medullary thick ascending limb apical and basolateral membranes

1998 ◽  
Vol 274 (3) ◽  
pp. F453-F462 ◽  
Author(s):  
Rickey Rivers ◽  
Anne Blanchard ◽  
Dominique Eladari ◽  
Francois Leviel ◽  
Michel Paillard ◽  
...  
Keyword(s):  
Plasma Membranes ◽  
Basolateral Membrane ◽  
Thick Ascending Limb ◽  
Membrane Structures ◽  
Membrane Unit ◽  
Small Surface ◽  
Basolateral Membranes ◽  
Medullary Thick Ascending Limb ◽  
Osmotic Water

The medullary thick ascending limb (MTAL) reabsorbs solute without water and concentrates [Formula: see text] in the interstitium without a favorable pH gradient, activities which require low water and NH3 permeabilities. The contributions of different apical and basolateral membrane structures to these low permeabilities are unclear. We isolated highly purified apical and basolateral MTAL plasma membranes and measured, by stopped-flow fluorometry, their permeabilities to water, urea, glycerol, protons, and NH3. Osmotic water permeability at 20°C averaged 9.4 ± 0.8 × 10−4 cm/s for apical and 11.9 ± 0.5 × 10−4cm/s for basolateral membranes. NH3 permeabilities at 20°C averaged 0.0023 ± 0.00035 and 0.0035 ± 0.00080 cm/s for apical and basolateral membranes, respectively. These values are consistent with those obtained in isolated perfused tubules and can account for known aspects of MTAL function in vivo. Because the apical and basolateral membrane unit permeabilities are similar, the ability of the apical membrane to function as the site of barrier function arises from its very small surface area when compared with the highly redundant basolateral membrane.

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