Difference in the Na affinity of Na(+)-K(+)-ATPase along the rabbit nephron: modulation by K

1990 ◽  
Vol 259 (2) ◽  
pp. F246-F250 ◽  
Author(s):  
C. Barlet-Bas ◽  
L. Cheval ◽  
C. Khadouri ◽  
S. Marsy ◽  
A. Doucet
Keyword(s):  
Atpase Activity ◽  
Thick Ascending Limb ◽  
Kidney Cells ◽  
Nephron Segments ◽  
Adaptive Property ◽  
Collecting Tubule ◽  
Pump Activity ◽  
K Concentration ◽  
Cortical Collecting Tubule

The sensitivity of Na(+)-K(+)-ATPase to Na was determined in single segments of rabbit nephron isolated by microdissection. In the cortical collecting tubule (CCT), Na(+)-K(+)-ATPase was threefold more sensitive to Na (apparent K0.5 approximately 3 mM) than in proximal convoluted tubule and cortical thick ascending limb (apparent K0.5 approximately 10 mM). Furthermore, increasing K concentration from 5 to greater than 100 mM markedly reduced the affinity of the pump for Na in all three nephron segments. In fact, the main shift in Na affinity occurred when K changed from 100 to 120 mM; in the CCT, increasing K concentration from 100 to 120 mM while maintaining Na concentration at 10 mM reduced Na(+)-K(+)-ATPase activity by greater than 35%. These findings confirm that, in kidney cells as in other cells, intracellular Na limits the rate of Na(+)-K(+)-ATPase. Thus any alteration of intracellular Na concentration modifies the pump activity in a way that contributes to the restoration of intracellular Na homeostasis. This adaptive property is particularly efficient in the collecting tubule in which the apparent K0.5 of the pump for Na is close to normal intracellular Na concentration. Furthermore, changes in intracellular K concentration, which usually accompany those of Na so as to maintain the total cation concentration constant, potentiate the regulatory role of Na through modifications of its affinity for the pump.

Regulation of renal Na-K-ATPase in the rat: effect of uninephrectomy

1986 ◽  
Vol 251 (3) ◽  
pp. F506-F512 ◽  
Author(s):  
S. K. Mujais ◽  
N. A. Kurtzman
Keyword(s):  
Enzyme Activity ◽  
Adrenal Gland ◽  
Atpase Activity ◽  
Thick Ascending Limb ◽  
Medullary Thick Ascending Limb ◽  
Collecting Tubule ◽  
Pars Recta ◽  
Intact Rats ◽  
Cortical Collecting Tubule

This study has examined the temporal profile and the segmental localization along the rat nephron of the increase in Na-K-ATPase produced by uninephrectomy, and the role of the adrenal gland in the generation of the increase in enzyme activity. In adrenal-intact rats, an increase in Na-K-ATPase activity in the cortical collecting tubule (CCT) was observed at 1 wk (140 +/- 13% of sham, P less than 0.05) and sustained at 2 wk (140 +/- 8% of sham, P less than 0.05). In contrast, the enhancement of enzyme activity in the proximal convoluted tubule (PCT) was transient (at 1 wk: 164 +/- 20% of sham, P less than 0.05; and at 2 wk: 97 +/- 9% of sham, P greater than 0.5). No changes in Na-K-ATPase activity were observed in the other nephron segments studied: pars recta, medullary thick ascending limb, cortical thick ascending limb, distal convoluted tubule, and medullary collecting tubule. In adrenalectomized rats, CCT enzyme activity was lower than in adrenal-intact rats (761 +/- 84 vs. 1,984 +/- 276 pmol X mm-1 X h-1, P less than 0.001) and was not altered by uninephrectomy (849 +/- 91 pmol X mm-1 X h-1, NS). We conclude that the increase in Na-K-ATPase activity following uninephrectomy is restricted to two segments of the nephron and follows a distinctive pattern in each. In the PCT a transient enhancement in enzyme activity is observed, whereas in the CCT the increase in Na-K-ATPase is sustained and requires the presence of an intact adrenal gland.

Stimulation of Na-K-ATPase in the rat collecting tubule by two diuretics: furosemide and amiloride

1984 ◽  
Vol 247 (3) ◽  
pp. F485-F490 ◽  
Author(s):  
G. E. Mernissi ◽  
A. Doucet
Keyword(s):  
Atpase Activity ◽  
Chronic Administration ◽  
Maximal Activity ◽  
Thick Ascending Limb ◽  
Sodium Permeability ◽  
Nephron Segments ◽  
Collecting Tubule ◽  
Pump Activity ◽  
Tubule Diameter ◽  
Stimulation Of

To test whether sodium availability controls the concentration of renal Na-K-ATPase, we evaluated the effect of chronic alterations in apical membrane sodium permeability in specific nephron segments on the maximal activity of Na-K-ATPase. For this purpose Na-K-ATPase activity was determined in nephron segments microdissected from rats treated continuously for 3-8 days with either furosemide or amiloride, two diuretics known to lower the apical permeability to sodium in the thick ascending limb and the collecting tubule, respectively. Unexpectedly, Na-K-ATPase activity was decreased neither in the thick ascending limb nor in the collecting tubule after administration of either drug. In fact, both diuretics paradoxically increased the pump activity by 60-150% in the collecting tubule. This stimulation of Na-K-ATPase activity was accompanied with an enhancement of the collecting tubule diameter. Stimulation of Na-K-ATPase was identical in the collecting tubule of diuretic-treated rats receiving spironolactone. These results suggest that Na-K-ATPase maximal activity is not controlled by sodium availability or by aldosterone under these conditions and that chronic administration of furosemide or amiloride induces Na-K-ATPase activity in the collecting tubule. This effect appears to be independent of aldosterone.

Regulation of renal Na+-K+-ATPase in the rat: role of increased potassium transport

1986 ◽  
Vol 251 (2) ◽  
pp. F199-F207
Author(s):  
S. K. Mujais ◽  
M. A. Chekal ◽  
J. P. Hayslett ◽  
A. I. Katz
Keyword(s):  
Enzyme Activity ◽  
Atpase Activity ◽  
Potassium Transport ◽  
High Potassium ◽  
Dietary Potassium ◽  
Collecting Tubule ◽  
Physiological Dose ◽  
Potassium Loading ◽  
Cortical Collecting Tubule

The purpose of this study was to characterize the alterations in collecting tubule Na+-K+-ATPase activity produced by sustained increments in dietary potassium in the rat and to evaluate the role of aldosterone in their generation. In adrenal-intact animals, feeding a high-potassium diet (10-fold that of control) or administration of a high physiological dose of aldosterone (5 micrograms X 100 g-1 X day-1), which simulates the delivery rate of this hormone during potassium loading (both for 7 days), caused marked increments in Na+-K+-ATPase activity in the cortical collecting tubule (CCT) but had no effect on the enzyme in the inner stripe of the medullary collecting tubule (MCT). A significant increase in enzyme activity was also observed after smaller dietary potassium increments (2.5 and 5 times the control) and after 4 (but not 2) days of dietary potassium load. In adrenalectomized rats provided with physiological replacement doses of corticosterone and aldosterone (0.8 micrograms X 100 g-1 X day-1), Na+-K+-ATPase activity in both CCT and MCT was similar to that of adrenal-intact controls but remained unchanged after 7 days on the potassium-enriched (10-fold) diet. In contrast, adrenalectomized animals receiving the high physiological dose of aldosterone displayed an increase in Na+-K+-ATPase activity of CCT comparable with that of adrenal-intact animals, whereas the enzyme activity in the MCT was unaffected. In conclusion, 1) following chronic potassium loading Na+-K+-ATPase activity increases significantly in the CCT with no change in its activity in the inner stripe of the MCT.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal memory after potassium adaptation: role of Na+-K+-ATPase

1988 ◽  
Vol 254 (6) ◽  
pp. F845-F850 ◽  
Author(s):  
S. K. Mujais
Keyword(s):  
Atpase Activity ◽  
Time Course ◽  
Base Line ◽  
Sprague Dawley ◽  
Membrane Transport Proteins ◽  
Sprague Dawley Rats ◽  
Potassium Adaptation ◽  
Collecting Tubule ◽  
Cortical Collecting Tubule

The present study was designed to explore the time course of the resolution of enhanced Na+-K+-ATPase activity in the cortical collecting tubule (CCT) and the parallel changes in renal K excretion that are characteristic of potassium adaptation. Potassium-adapted male Sprague-Dawley rats manifested an enhanced kaliuretic response to an acute intravenous load of KCl and a doubling of Na+-K+-ATPase activity in the CCT. Withdrawal of dietary K loading from these adapted rats was associated with a gradual resolution of these adaptive biochemical (t1/2 of Na+-K+-ATPase return to base line 48 h) and excretory changes. During this resolution phase, however, a temporal discrepancy was uncovered between the change in dietary K and the slower changes in enzyme activity and renal K excretion with a persistence of the enhanced kaliuresis leading to a negative K balance. We conclude that the slow inactivation, after withdrawal of K loading, of the increased membrane transport proteins of K adaptation, will manifest as a renal memory of the antecedent excretory requirements.

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)

Na+,K+-ATPase activity and hormones in single nephron segments from nephrotic rats

1991 ◽  
Vol 80 (6) ◽  
pp. 599-604 ◽  
Author(s):  
B. Vogt ◽  
H. Favre
Keyword(s):  
Nephrotic Syndrome ◽  
Atpase Activity ◽  
Hormonal Regulation ◽  
Sodium Balance ◽  
Sodium Retention ◽  
Twofold Increase ◽  
Nephron Segments ◽  
Endogenous Ouabain ◽  
Collecting Tubule ◽  
Cortical Collecting Tubule

1. In the nephrotic syndrome the kidneys retain salt and water, which leads to oedema formation. The site of this sodium retention has been localized in the cortical collecting tubule by micropuncture studies. Whether or not this phenomenon is an intrinsic renal problem or is the consequence of changes in hormonal activities is still a matter of discussion. 2. Using the model of puromycin aminonucleoside-induced nephrotic syndrome in the rat, we measured Na+,K+-ATPase activity in nephron segments from control and nephrotic rats and investigated the regulatory role of aldosterone and endogenous-ouabain-displacing factor. 3. Nephrotic animals had a twofold increase in Na+,K+-ATPase activity in the cortical collecting tubule only (control versus nephrotic: 1065 ± 68 versus 2081 ± 274 pmol h−1 mm−1, P = 0.036), which was not modified by adrenalectomy and was independent of the kidney content of endogenous ouabain-displacing factor. Na+,K+-ATPase activity in the cortical collecting tubule correlated with the sodium balance in both control and nephrotic rats. 4. The data are consistent with the view that sodium retention in this model of the nephrotic syndrome is a primary event, i.e. an increase in sodium transport throughout the cortical collecting tubule expressed as a twofold increase in Na+,K+-ATPase activity which is no longer under hormonal regulation (aldosterone and endogenous ouabain-displacing factor).

Changes in tubular basolateral membrane markers after chronic DOCA treatment

1983 ◽  
Vol 245 (1) ◽  
pp. F100-F109 ◽  
Author(s):  
G. El Mernissi ◽  
D. Chabardes ◽  
A. Doucet ◽  
A. Hus-Citharel ◽  
M. Imbert-Teboul ◽  
...  
Keyword(s):  
Adenylate Cyclase ◽  
Atpase Activity ◽  
Protein Content ◽  
Basolateral Membrane ◽  
Chronic Administration ◽  
Distal Nephron ◽  
Nephron Segments ◽  
Collecting Tubule ◽  
Nephron Segment ◽  
Cortical Collecting Tubule

Chronic administration of DOCA to rabbits is known to increase the surface area of the basolateral membrane and the Na-K-ATPase activity of the cortical collecting tubule (CCT). We attempted to ascertain 1) whether Na-K-ATPase is the only basolateral membrane marker induced by DOCA, and 2) whether CCT is the only nephron segment affected by this steroid. We measured the activity of Na-K-ATPase and adenylate cyclase (AC) and the protein content of nephron segments microdissected from control and DOCA-treated rabbits. Morphogenic effects of DOCA, assessed by 30-60% increases in protein content, were specifically observed in the distal convoluted tubule, CCT, and medullary collecting tubule. When expressed as a function of tubular length, Na-K-ATPase activity rose from 80 to 200% in all these segments, whereas the increments in AC of 40-70%, observed in response to four different hormones, occurred only in some of them. When expressed as a function of protein content, Na-K-ATPase activity increased but AC activity remained unchanged. This study indicates that the morphogenic action resulting from chronic DOCA administration affects the entire rabbit distal nephron. During this action Na-K-ATPase is the preferentially induced enzyme.

NEM-sensitive ATPase activity in rat nephron: effect of metabolic acidosis and alkalosis

1990 ◽  
Vol 258 (2) ◽  
pp. F297-F304 ◽  
Author(s):  
S. Sabatini ◽  
M. E. Laski ◽  
N. A. Kurtzman
Keyword(s):  
Enzyme Activity ◽  
Metabolic Acidosis ◽  
Atpase Activity ◽  
Collecting Duct ◽  
Proximal Convoluted Tubule ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Chronic Metabolic Acidosis ◽  
Collecting Tubule ◽  
Cortical Collecting Tubule

The present study was designed to quantitate the amount and to map the localization of N-ethylmaleimide (NEM)-sensitive adenosinetriphosphatase (ATPase) activity in microdissected segments of the rat nephron. After complete nephron mapping the effect of chronic metabolic acidosis and alkalosis on enzyme activity was determined. In control animals the highest enzyme activity was found in the early proximal convoluted tubule of juxtamedullary nephrons; superficial early proximal tubule as well as medullary and cortical thick ascending limbs and collecting ducts also contained substantial activity. Enzyme activity in the papillary collecting duct before entry into the ducts of Bellini was 329 +/- 93 pmol.mm-1.h-1 (n = 8); after entry, however, enzyme activity was approximately one-fourth that value (60 +/- 9 pmol.mm-1.h-1, n = 8, P less than 0.01). No NEM-sensitive ATPase activity was found in the thin limbs of the loop of Henle. Enzyme activity increased in both the medullary and cortical thick ascending limbs as well as in the cortical collecting tubule in response to NH4Cl-induced chronic metabolic acidosis; in the cortical collecting duct, metabolic acidosis increased maximum activity (Vmax) but did not change Michaelis-Menten constant (Km). In the proximal convoluted tubule, enzyme activity decreased with metabolic acidosis. Bicarbonate loading had no effect on enzyme activity except in the most distal portion of the collecting duct where it was stimulated. These results show that NEM-sensitive ATPase activity exists throughout much of the rat nephron. These data suggest that both the cortical collecting tubule and thick ascending limb are regulatory sites of distal urinary acidification during acid loading.

Characterization of K-ATPase activity in distal nephron: stimulation by potassium depletion

1987 ◽  
Vol 253 (3) ◽  
pp. F418-F423 ◽  
Author(s):  
A. Doucet ◽  
S. Marsy
Keyword(s):  
Atpase Activity ◽  
Rat Kidney ◽  
Intercalated Cells ◽  
Distal Nephron ◽  
Morphological Alterations ◽  
Nephron Segments ◽  
Collecting Tubule ◽  
K Depletion ◽  
Cortical Collecting Tubule

Intercalated cells of the distal segments of the mammalian nephron are able to reabsorb K through an active mechanism, particularly during K depletion. However, the molecular basis of this transport is unknown. Therefore, we attempted to determine whether a K-ATPase similar to K-H-ATPase described in gastric mucosa and colon might be present in segments of the distal nephron and thereby account for active K reabsorption. K-stimulated ATPase activity was detected in microdissected segments of rabbit nephron: its activity was proportional to the density of intercalated cells, since it was highest in the connecting tubule, intermediate in the cortical collecting tubule, lowest in the outer medullary collecting tubule, and was not detectable in all other nephron segments. K-ATPase had a high affinity for K (Km approximately equal to 0.2-0.4 mM), was inhibited by vanadate and omeprazole, and was insensitive to ouabain, indicating that it is different from Na+-K+-ATPase but similar to K-H-ATPase. In the rat kidney, K-ATPase was also detected in the collecting tubule and its activity was markedly increased (+100-200%) following K depletion. This stimulation occurred before morphological alterations and might therefore be a primary event responsible for K conservation during K depletion. In summary, these results demonstrate the presence of a vanadate-sensitive, ouabain-insensitive K-ATPase activity in distal nephron segments of mammalian tubules. It is suggested that K-ATPase activity originates in intercalated cells where it might account, at least in part, for K reabsorption.

PGE2, PGF2 alpha, 6-keto-PGF1 alpha, and TxB2 synthesis along the rabbit nephron

1987 ◽  
Vol 252 (1) ◽  
pp. F53-F59 ◽  
Author(s):  
N. Farman ◽  
P. Pradelles ◽  
J. P. Bonvalet
Keyword(s):  
Arachidonic Acid ◽  
Prostaglandin E2 ◽  
Proximal Tubule ◽  
Enzyme Immunoassay ◽  
Thick Ascending Limb ◽  
Pge2 Synthesis ◽  
Nephron Segments ◽  
Prostaglandin F2 Alpha ◽  
Collecting Tubule ◽  
Cortical Collecting Tubule

The capacity of synthesis of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), 6-keto-PGF1 alpha, and thromboxane (TxB2) along the rabbit nephron was determined. A sensitive enzyme immunoassay was applied to isolated nephron segments, from the glomerulus to the terminal collecting tubule. The three prostaglandins and thromboxane (PG) were measured on the same samples after incubation in the presence of arachidonic acid. In the glomerulus, PGE2 synthesis (29.4 +/- 3.3 pg X glomerulus-1 X 30 min-1) represented 60% of the sum of the four PGs. PGF2 alpha and 6-keto-PGF1 alpha represented 22 and 17%, respectively, and TxB2 1.4%. The contribution of each PG to tubular synthesis was different, since at least 90% of PG synthesis consisted of PGE2. In the medullary collecting tubule (MCT), by far the major tubular site of PG synthesis, it was 809.6 +/- 140.8 pg X mm-1 X 30 min-1 for PGE2, 17.7 +/- 7.2 for PGF2 alpha, 8.3 +/- 1.9 for 6-keto-PGF1 alpha and 0.24 +/- 0.08 for TxB2. These relative proportions were roughly respected all along the tubule. Values were much lower in the convoluted and straight portions of the proximal tubule (proximal convoluted tubule: PGE2 8.2 +/- 2.0, PGF2 alpha 0.4 +/- 0.06, 6-keto-PGF1 alpha 0.26 +/- 0.04, TxB2 0.017) and the medullary and cortical thick ascending limb of the loop. They increased regularly along the distal structures of the tubule (light portion of the cortical collecting tubule (CCT1): PGE2 228.3 +/- 20.4, PGF2 alpha 4.34 +/- 0.6, 6-keto-PGF1 alpha 1.8 +/- 0.3, TxB2 0.22 +/- 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)

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