scholarly journals Kidney outer medulla mitochondria are more efficient compared with cortex mitochondria as a strategy to sustain ATP production in a suboptimal environment

2018 ◽  
Vol 315 (3) ◽  
pp. F677-F681 ◽  
Author(s):  
Tomas A. Schiffer ◽  
Håkan Gustafsson ◽  
Fredrik Palm
Keyword(s):  
Oxygen Affinity ◽  
Kidney Cortex ◽  
Thick Ascending Limb ◽  
Kidney Medulla ◽  
Atp Production ◽  
Medullary Thick Ascending Limb ◽  
Functional Problem ◽  
Nephron Segment ◽  
Regional Renal Blood Flow

The kidneys receive ~25% of cardiac output, which is a prerequisite to maintain sufficient glomerular filtration rate. However, both intrarenal regional renal blood flow and tissue oxygen levels are heterogeneous with decreasing levels in the inner part of the medulla. These differences, in combination with the heterogeneous metabolic activity of the different nephron segment located in the different parts of the kidney, may constitute a functional problem when challenged. The proximal tubule and the medullary thick ascending limb of Henle are considered to have the highest metabolic rate, which is related to the high mitochondria content needed to sustain sufficient ATP production from oxidative phosphorylation to support high electrolyte transport activity in these nephron segments. Interestingly, the cells located in kidney medulla function at the verge of hypoxia, and the mitochondria may have adapted to the surrounding environment. However, little is known about intrarenal differences in mitochondria function. We therefore investigated functional differences between mitochondria isolated from kidney cortex and medulla of healthy normoglycemic rats by using high-resolution respirometry. The results demonstrate that medullary mitochondria had a higher degree of coupling, are more efficient, and have higher oxygen affinity, which would make them more suitable to function in an environment with limited oxygen supply. Furthermore, these results support the hypothesis that mitochondria of medullary cells have adapted to the normal hypoxic in vivo situation as a strategy of sustaining ATP production in a suboptimal environment.

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.

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.

Metabolism of C14-labeled substrates by rabbit kidney cortex and medulla

1962 ◽  
Vol 203 (1) ◽  
pp. 27-36 ◽  
Author(s):  
James B. Lee ◽  
Vernon K. Vance ◽  
George F. Cahill
Keyword(s):  
Fatty Acids ◽  
The Other ◽  
High Rate ◽  
Rabbit Kidney ◽  
Kidney Cortex ◽  
Anaerobic Conditions ◽  
Kidney Medulla ◽  
Bicarbonate Buffer ◽  
Radioactive Substrate

Slices of rabbit kidney cortex and medulla were incubated for 90 min at 38 C in Krebs-Ringer bicarbonate buffer containing C14 labeled substrate. In addition to substrate disappearance and concentrations of glycogen and fatty acids, measurements were made of the amount of radioactive substrate incorporated into CO2, glycogen, and fatty acids per gram of wet tissue. Glucose, fructose, mannose, glycerol, pyruvate, and palmitate were oxidized to a significantly greater extent by cortex than medulla. The concentration of glycogen in kidney medulla was twice that of cortex and was maintained at initial concentrations only in the presence of glucose, which showed a significantly greater incorporation into medullary glycogen than did the other substrates. Under pure anaerobic conditions simulating those in vivo, the present study suggests that the metabolism of medulla is almost exclusively glucose-dependent anaerobic glycolysis. On the other hand, the cortex is capable of utilizing a variety of substrates for a high rate of aerobic metabolism.

Regulation by glucocorticoids and osmolality of expression of ROMK (Kir 1.1), the apical K channel of thick ascending limb

2003 ◽  
Vol 284 (5) ◽  
pp. F977-F986 ◽  
Author(s):  
Morgan Gallazzini ◽  
Amel Attmane-Elakeb ◽  
David B. Mount ◽  
Steven C. Hebert ◽  
Maurice Bichara
Keyword(s):  
Protein Expression ◽  
In Vivo Studies ◽  
K Channel ◽  
Thick Ascending Limb ◽  
Rt Pcr ◽  
Immunoblotting Analysis ◽  
Medullary Thick Ascending Limb ◽  
Nacl Concentration ◽  
Mrna And Protein Expression

Mechanisms of regulation of ROMK channel mRNA and protein expression in medullary thick ascending limb (MTAL) were assessed in rat MTAL fragments incubated for 7 h. ROMK mRNA was quantified by quantitative RT-PCR and ROMK protein by immunoblotting analysis of crude membranes. Medium hyperosmolality (450 mosmol/kgH2O; NaCl plus urea added to isoosmotic medium) increased ROMK mRNA ( P < 0.04) and protein ( P < 0.006), and 10 nM dexamethasone also increased ROMK mRNA ( P < 0.02). Hyperosmolality and dexamethasone had no additive effects on ROMK mRNA. NaCl alone, but not urea or mannitol, reproduced the hyperosmolality effect on ROMK mRNA. 1-Deamino-(8-d-arginine) vasopressin (1 nM) or 0.5 mM 8-bromo-cAMP had no effect per se on ROMK mRNA and protein. However, 8-bromo-cAMP abolished the stimulatory effect of dexamethasone on ROMK mRNA in the isoosmotic but not in the hyperosmotic medium ( P < 0.004). In in vivo studies, the abundance of ROMK protein and mRNA increased in adrenalectomized (ADX) rats infused with dexamethasone compared with ADX rats ( P < 0.02). These results establish glucocorticoids and medium NaCl concentration as direct regulators of MTAL ROMK mRNA and protein expression, which may be modulated by cAMP-dependent factors.

Consequences of differential effects of ADH and other peptide hormones on thick ascending limb of mammalian kidney

1991 ◽  
Vol 260 (6) ◽  
pp. R1023-R1035 ◽  
Author(s):  
C. De Rouffignac ◽  
A. Di Stefano ◽  
M. Wittner ◽  
N. Roinel ◽  
J. M. Elalouf
Keyword(s):  
Term Treatment ◽  
Thick Ascending Limb ◽  
Adenylate Cyclase System ◽  
Nacl Transport ◽  
Differential Effects ◽  
Physiological Relevance ◽  
Long Term Treatment ◽  
Nephron Segment

Several hormones stimulate the adenylate cyclase system of the thick ascending limb (TAL). There are, however, some species differences concerning the cyclase sensitivity and the hormonal response in this nephron segment. In the mouse, antidiuretic hormone (ADH), parathyroid hormone, glucagon, calcitonin, and isoproterenol stimulate Na+, Cl-, Mg2+, and Ca2+ transports in the cortical TAL, whereas ADH, glucagon, and isoproterenol stimulate NaCl transport only in the medullary TAL. Many of these effects are different from those previously described for the corresponding segments of the rabbit nephron. The close similarity of the cyclase responsiveness to hormones of the mouse and rat TALs makes it possible to interpret the micropuncture data obtained in vivo in the rat superficial (S) and juxtamedullary (JM) nephrons, in the light of the in vitro data obtained in the mouse. Long-term treatment of Brattleboro rats with ADH also elicits differential effects along the TAL. Their consequences on the function of the S and JM nephrons are also examined. There are several indications supporting the view that the newly described hormonal effects in the mouse and rat are of physiological relevance.

Effect of metabolic acidosis and alkalosis on NEM-sensitive ATPase in rat nephron segments

1992 ◽  
Vol 262 (4) ◽  
pp. F583-F590 ◽  
Author(s):  
C. Khadouri ◽  
S. Marsy ◽  
C. Barlet-Bas ◽  
L. Cheval ◽  
A. Doucet
Keyword(s):  
Metabolic Acidosis ◽  
Atpase Activity ◽  
Thick Ascending Limb ◽  
Nephron Segments ◽  
Medullary Thick Ascending Limb ◽  
Henle's Loop ◽  
Collecting Tubule ◽  
Nephron Segment ◽  
Electrogenic Proton Pump ◽  
Chloride Treatment

An N-ethylmaleimide (NEM)-sensitive adenosinetriphosphatase (ATPase) displaying the kinetic and pharmacological properties of an electrogenic proton pump has been described in the different segments of rat nephron, where it mediates part of the active tubular proton secretion. This study was therefore designed to evaluate whether changes in urinary acidification observed during metabolic acidosis or alkalosis were associated with alterations of the activity of tubular NEM-sensitive ATPase, and if so, to localize the nephron segments responsible for these changes. Within 1 wk after the onset of ammonium chloride treatment, rats developed a metabolic acidosis, and NEM-sensitive ATPase activity was markedly increased in the medullary thick ascending limb of Henle's loop and outer medullary collecting tubule, and slightly increased in the cortical collecting tubule. Conversely, treatment with sodium bicarbonate induced a metabolic alkalosis that was accompanied by decreased NEM-sensitive ATPase activity in medullary thick ascending limb and outer medullary collecting tubule. NEM-sensitive ATPase activity was not altered in any other nephron segment tested in alkalotic and acidotic rats, i.e., the proximal tubule and the cortical thick ascending limb of Henle's loop. Changes qualitatively similar were observed as soon as 3 h after the onset of NaHCO3 or NH4Cl-loading. In the medullary collecting tubule, alterations of NEM-sensitive ATPase activity are in part due to hyperaldosteronism observed in both acidotic and alkalotic rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium transport in the proximal convoluted tubule and loop of Henle of rats made diabetic with streptozotocin

1991 ◽  
Vol 131 (3) ◽  
pp. 373-380 ◽  
Author(s):  
H. O. Garland ◽  
P. J. Harris ◽  
T. O. Morgan
Keyword(s):  
Calcium Absorption ◽  
Diabetic Rats ◽  
Thick Ascending Limb ◽  
Loop Of Henle ◽  
Fluid Absorption ◽  
New Information ◽  
Causative Factors ◽  
Nephron Segment ◽  
Acute Changes

ABSTRACT In-vivo microperfusion was used to localize the reabsorptive defect responsible for the hypercalciuria of diabetes mellitus and to investigate possible causative factors. Unidirectional proximal calcium absorption was not significantly different in rats made diabetic with streptozotocin compared with controls, providing evidence against the involvement of this nephron segment in the phenomenon. Calcium absorption by the loop of Henle, was however, significantly (P<0·01) lower in diabetic animals (32·1 ±1·2 vs 40·4±0·6 pmol/min). Based on our knowledge of calcium movements within the loop, it is likely that the reabsorptive defect resides within the thick ascending limb. The calcium lesion was found to be independent of acute changes in intraluminal glucose concentration and could not be corrected by acute insulin treatment. The study also provides new information on the relationship between intratubular glucose and fluid movements in the rat nephron. In diabetic rats a proximal perfusate containing 30 mmol glucose/l resulted in fluid absorption comparable with that seen in control rats perfused with 5 mmol glucose/l. However, intraluminal glucose had a stimulatory effect on fluid absorption in the loop of Henle of diabetic rats (10·7 ±0·5 vs 7·9±0·4 nl/min; P<0·01). Journal of Endocrinology (1991) 131, 373–380

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