Effect of adrenalectomy on NEM-sensitive ATPase along rat nephron and on urinary acidification

1987 ◽  
Vol 253 (3) ◽  
pp. F495-F499 ◽  
Author(s):  
C. Khadouri ◽  
S. Marsy ◽  
C. Barlet-Bas ◽  
A. Doucet
Keyword(s):  
Atpase Activity ◽  
Automatic Determination ◽  
Outer Medulla ◽  
Proton Secretion ◽  
Nephron Segments ◽  
Collecting Tubule ◽  
Single Nephron ◽  
Electrogenic Proton Pump ◽  
Adrenalectomized Rats

An N-ethyl-maleimide (NEM)-sensitive ATPase that displays the properties of an electrogenic proton pump has been described in the different segments of the rat nephron where it mediates part of the active tubular proton secretion. Because corticosteroids are known to control kidney acidification, we evaluated whether or not NEM-sensitive ATPase is a target of corticosteroids in some nephron segments. For this purpose we measured NEM-sensitive ATPase activity in the different segments of nephron microdissected from normal and adrenalectomized rats. Results indicate that within 1 wk after adrenalectomy NEM-sensitive ATPase activity was markedly decreased in both cortical and outer medullary portions of the collecting tubule (cortex, from 398 +/- 12 (+/-SE) to 145 +/- 20; outer medulla, from 293 +/- 21 to 112 +/- 14 pmol X mm-1 X h-1); however, it was not altered in any other segment of the nephron. These results demonstrate that kidney NEM-sensitive ATPase is under the control of corticosteroids and suggest that mineralocorticoids rather than glucocorticoids are involved in this regulation that specifically occurs in mineralocorticoid-sensitive nephron segments. This paper also describes a new computerized method for the automatic determination of the length of single nephron segments.

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)

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.

Gluco- and mineralocorticoids control adenylate cyclase in specific nephron segments

1990 ◽  
Vol 258 (4) ◽  
pp. F812-F820 ◽  
Author(s):  
A. Doucet ◽  
C. Barlet-Bas ◽  
S. Siaume-Perez ◽  
C. Khadouri ◽  
S. Marsy
Keyword(s):  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Mechanism Of Action ◽  
Thick Ascending Limb ◽  
Aluminum Fluoride ◽  
Camp Production ◽  
Nephron Segments ◽  
Glucocorticoid Administration ◽  
Collecting Tubule ◽  
Adrenalectomized Rats

Adrenal insufficiency is associated with an impairment of kidney diluting and concentrating ability, defects that may result from alterations of vasopressin-induced adenosine 3',5'-cyclic monophosphate (cAMP) production. The purpose of this study were 1) to localize the sites of decreased vasopressin-stimulated adenylate cyclase (AC) activity along the nephron of adrenalectomized rats; 2) to determine whether the response of AC to other hormones is altered by adrenalectomy; 3) to evaluate whether changes in AC are due to the deficiency in mineralocorticoids and/or glucocorticoids; and 4) to characterize the mechanism of action of corticosteroids on the AC system. Results indicate that adrenalectomy reduced AC stimulation by vasopressin, glucagon, and calcitonin in the thick ascending limb, whereas only the response to vasopressin decreased in the collecting tubule. Glucocorticoid administration curtailed adrenalectomy-induced alterations of AC in the thick ascending limb, whereas that in the collecting tubule was prevented by mineralocorticoids. Adrenalectomy did not alter forskolin-stimulated AC, whereas it decreased responses to aluminum fluoride and cholera toxin. Finally, alterations of fluoride- and cholera toxin-stimulated AC were prevented by glucocorticoid and mineralocorticoid repletion in the thick ascending limb and collecting tubule, respectively.

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.

Relationship between mineralocorticoids and renal Na+-K+-ATPase: sodium reabsorption

1977 ◽  
Vol 233 (6) ◽  
pp. F593-F599
Author(s):  
C. Westenfelder ◽  
G. J. Arevalo ◽  
R. L. Baranowski ◽  
N. A. Kurtzman ◽  
A. I. Katz
Keyword(s):  
Atpase Activity ◽  
Specific Activity ◽  
Isotonic Saline ◽  
Sodium Reabsorption ◽  
Outer Medulla ◽  
High Salt Diet ◽  
Salt Diet ◽  
Relative Contribution ◽  
Adrenalectomized Rats ◽  
Stimulation Of

To evaluate the mechanism responsible for the effect of deoxycorticosterone acetate (DOCA) on renal Na+-K+-ATPase, we compared the relative contribution of this hormone and of increased absolute sodium reabsorption (TNa) to the restoration of the enzyme in kidneys of adrenalectomized rats. In study A, adrenalectomized animals maintained on a salt-free diet received 5 mg/kg per day DOCA i.m., while sham-operated and untreated adrenalectomized rats receiving the same diet served as controls. Absolute TNa and Na+-K+-ATPase specific activity in the cortex and outer medulla of DOCA-treated rats were similar to those measured in untreated adrenalectomized animals, but were significantly lower than in sham-operated controls. In study B, the adrenalectomized rats did not receive DOCA but were fed a high salt diet and received isotonic saline, 50 ml/kg per day s.c. Absolute TNa and cortical and medullary Na+-K+-ATPase specific activity were significantly higher in the salt-loaded group than in both adrenalectomized and sham-operated rats deprived of salt. These results suggest that absolute sodium reabsorption is a major determinant of renal Na+-K+-ATPase activity, and that the effect of DOCA on this enzyme is secondary to its stimulation of absolute tubular sodium transport.

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.

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.

K(+)-ATPase-mediated Rb+ transport in rat collecting tubule: modulation during K+ deprivation

1991 ◽  
Vol 260 (6) ◽  
pp. F800-F805 ◽  
Author(s):  
L. Cheval ◽  
C. Barlet-Bas ◽  
C. Khadouri ◽  
E. Feraille ◽  
S. Marsy ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Initial Rate ◽  
Apparent Affinity ◽  
Nephron Segments ◽  
Collecting Tubule ◽  
Collecting Tubules ◽  
K Transport

To evaluate the involvement of K(+)-ATPase activity in K+ transport in the terminal segments of the rat nephron, we searched for the existence of a component of Rb+ uptake into microdissected segments of collecting tubule associated with the activity of this ATPase. Results indicated that K(+)-ATPase is stimulated by K+ and by Rb+ in a similar fashion and that it is specifically inhibited by the imidazopyridine Sch 28080 (apparent affinity approximately 5 x 10(-7) M). In both cortical and outer medullary collecting tubules (CCT and MCT) of normal rats, 10(-4) M Sch 28080 significantly inhibited the initial rate of Rb+ uptake. Sch 28080-sensitive Rb+ uptake in these two nephron segments was not altered by ouabain, as K(+)-ATPase activity. Finally, both K(+)-ATPase activity and Sch 28080-sensitive Rb+ uptake were increased by similar factors in the CCT and MCT of rats fed a K(+)-depleted diet for 3 days. In these two nephron segments, the apparent stoichiometry of K(+)-ATPase was 1 Rb+:1 ATP. These results demonstrate that K(+)-ATPase reflects the activity of a K+ pump that is pharmacologically similar to the gastric H(+)-K+ pump.

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