Proximal tubule Na+-K+-ATPase activity is inhibited during high-salt diet: evidence for DA-mediated effect

1988 ◽  
Vol 254 (6) ◽  
pp. F795-F801 ◽  
Author(s):  
A. Bertorello ◽  
T. Hokfelt ◽  
M. Goldstein ◽  
A. Aperia
Keyword(s):  
Atpase Activity ◽  
Proximal Tubule ◽  
Significant Inhibition ◽  
High Salt ◽  
Acid Decarboxylase ◽  
Thick Ascending Limb ◽  
Amino Acid Decarboxylase ◽  
Physiological Importance ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition

Locally produced dopamine (DA) causes a reversible and dose-dependent inhibition in Na+-K+-ATPase activity in rat proximal tubule (PT) segments [A. Aperia, A. Bertorello, and I. Seri. Am. J. Physiol. 252 (Renal Fluid Electrolyte Physiol. 21): F32–F45, 1987.]. To examine whether this effect might be of physiological importance, rats were given normal-salt (NS) or high-salt (HS) diet for 10 days. HS diet significantly increased Na excretion but did not alter glomerular filtration rate (GFR). Benserazide (Bz), an inhibitor of the enzyme L-aromatic amino acid decarboxylase (AADC) that converts L-dopa to DA, significantly attenuated the natriuresis in HS rats but had no effect on GFR. By use of immunofluorescence (IF) studies AADC was localized to the PT. Specific AADC IF was not observed in the medulla. In AADC-positive PT segments, Na+-K+-ATPase activity was significantly lower in HS rats than in NS rats (P less than 0.001). In AADC-negative medullary thick ascending limb, Na+-K+-ATPase activity was the same in NS and HS rats. If HS rats were given Bz just before study, PT Na+-K+-ATPase activity increased significantly and was not different from Na+-K+-ATPase activity in PT segments from NS rats. Bz had no significant effect on PT Na+-K+-ATPase activity in NS rats. In PT segments from Bz-treated rats, DA inhibited Na+-K+-ATPase activity already at a dose of 10(-8) M, whereas in segments from NS rats, significant inhibition of Na+-K+-ATPase activity was not observed until DA was increased to 10(-7) M.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitochondrial injury: an early event in cisplatin toxicity to renal proximal tubules

1990 ◽  
Vol 258 (5) ◽  
pp. F1181-F1187 ◽  
Author(s):  
H. R. Brady ◽  
B. C. Kone ◽  
M. E. Stromski ◽  
M. L. Zeidel ◽  
G. Giebisch ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Proximal Tubule ◽  
Threshold Concentration ◽  
Early Event ◽  
Intact Cells ◽  
Mitochondrial Injury ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition ◽  
Early Effects ◽  
K Transport

Oxygen consumption (QO2) and net K+ transport were studied in rabbit proximal tubule suspensions to define the early effects of cisplatin on proximal tubule function. Cisplatin caused dose-dependent inhibition of QO2, which was delayed in onset. The concentration of cisplatin required for inhibition decreased as the duration of exposure was increased [40-min exposure, threshold concentration of 10(-4) M, inhibitor constant (Ki) of 10(-3) M; 4-h exposure, threshold concentration of 3 X 10(-5) M, Ki of 10(-4) M]. Both ouabain-sensitive and ouabain-insensitive QO2 were reduced, indicating inhibition of all adenosinetriphosphatases, including Na(+)- K(+)-ATPase activity. There was a parallel fall in ouabain-sensitive net K+ transport and cytosolic K+ content, confirming the latter observation. Na(+)-K(+)-ATPase activity was unchanged in cell membranes prepared by hypotonic lysis from cisplatin-treated tubules, indicating an indirect cytosol-dependent mechanism of enzyme inhibition. Nystatin-stimulated QO2 was reduced in cisplatin-treated tubules, excluding inhibition of Na+ entry as the mechanism of injury and suggesting mitochondrial injury. The latter was confirmed by measurement of carbonylcyanide-m-chlorophenylhydrazone (CCCP)-uncoupled QO2 in intact cells and ADP-stimulated (state 3) QO2 in digitonin-permeabilized tubules. Furthermore, by maximally stimulating mitochondrial respiration with CCCP and nystatin, it was possible to demonstrate mitochondrial injury at a time when basal QO2 and K+ transport were apparently normal. These data suggest that mitochondrial injury is a central event in cisplatin toxicity to the proximal tubule.

Role of Na+/H+ exchanger NHE3 in nephron function: micropuncture studies with S3226, an inhibitor of NHE3

2000 ◽  
Vol 278 (3) ◽  
pp. F375-F379 ◽  
Author(s):  
Volker Vallon ◽  
Jan-Robert Schwark ◽  
Kerstin Richter ◽  
Max Hropot
Keyword(s):  
Proximal Tubule ◽  
Proximal Convoluted Tubule ◽  
Tubuloglomerular Feedback ◽  
Thick Ascending Limb ◽  
Loop Of Henle ◽  
Luminal Membrane ◽  
Henle's Loop ◽  
Dependent Inhibition ◽  
Proximal Tubular ◽  
Dose Dependent Inhibition

Na+/H+ exchanger NHE3 is expressed in the luminal membrane of proximal tubule and thin and thick ascending limb of Henle's loop. To further define its role, the novel NHE3 inhibitor S3226 was employed in micropuncture experiments in nephrons with superficial glomeruli of anesthetized rats. Microperfusion of proximal convoluted tubule with S3226 revealed a dose-dependent inhibition of reabsorption (IC50 of 4–5 μM) with a maximum inhibition of 30% for fluid and Na+. During microperfusion of Henle's loop (last superficial proximal to first superficial distal tubular loop), no effect of S3226 (10 or 30 μM) on the reabsorption of fluid or Na+ was observed. Finally, S3226 (30 μM) left the tubuloglomerular feedback response unaltered as determined by the fall in proximal tubular stop-flow pressure in response to increasing loop of Henle perfusion rate. These studies indicate that NHE3 significantly contributes to fluid and Na+ reabsorption in proximal convoluted tubule. NHE3 appears not to significantly contribute to fluid or Na+reabsorption in the loop of Henle (including the S3 segment of proximal tubule) or macula densa control of nephron filtration.

scholarly journals Chemical aspect of the influence of cobalt ions on atpase activity

2000 ◽  
Vol 65 (7) ◽  
pp. 507-515 ◽  
Author(s):  
Ljubica Vujisic ◽  
Danijela Krstic ◽  
Jovan Vucetic
Keyword(s):  
Experimental Data ◽  
Plasma Membrane ◽  
Atpase Activity ◽  
Kinetic Analysis ◽  
Synaptic Plasma Membrane ◽  
Cobalt Ions ◽  
Dependent Inhibition ◽  
Ic50 Values ◽  
Dose Dependent Inhibition ◽  
Dose Dependent

The influence of Co 2+ ions on the activities of Na+/K+-ATPase and Mg2+ -ATPase, enzymes from rat brain synaptic plasma membrane, was studied. The aim of this study was to investigate the inhibition of both ATPases activities byexposure tocobalt ions as a function of experimentally added CoSO4. The "free" Co2+ concentrations in the reaction mixturewere also calculated and discussed. CoSO4 induced a dose-dependent inhibition of both enzymes. The IC50 values of Co 2+, as calculated from the experimental curves, were 168 mM for Na+/K+-ATPase and 262 mMfor Mg 2+-ATPase, and for the recalculated free Co 2+ concentration 75.4 mM for Na+/K+-ATPase and 136 mM for Mg 2+-ATPase. The obtained linear Dixon's plot for Na+/K+-ATPase implies equilibium binding of cobalt with inhibitory sites on the enzyme. The kinetic parameters for both enzymes in presence and absence of CoSO4 were calculated from the experimental data. The results of the kinetic analysis show that inhibition of Na+/K+-ATPase induced by CoSO4 is non-competitive, and for Mg 2+-ATPase that there are two sites of different sensitivities or two different enzymes.

Influence of Na+ intake on dopamine-induced inhibition of renal cortical Na(+)-K(+)-ATPase

1990 ◽  
Vol 258 (1) ◽  
pp. F52-F60 ◽  
Author(s):  
I. Seri ◽  
B. C. Kone ◽  
S. R. Gullans ◽  
A. Aperia ◽  
B. M. Brenner ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Sodium Intake ◽  
Dietary Sodium ◽  
Acid Decarboxylase ◽  
Proximal Tubule Cell ◽  
Maximal Velocity ◽  
Tubule Cell ◽  
Amino Acid Decarboxylase ◽  
Cell Cytosol ◽  
In Cells

The enzyme L-amino acid decarboxylase (L-AADC), found in abundance in rat proximal tubule cell cytosol, converts L-dopa to dopamine. Dopamine, in turn, suppresses proximal tubule sodium transport by inhibiting Na(+)-K(+)-ATPase activity. We sought to determine whether changes in dietary sodium intake in rats lead to adaptation of dopamine formation and dopamine-induced Na(+)-K(+)-ATPase inhibition. In rats on a high-salt (HS) diet, the maximal velocity (Vmax) of renal cortical L-AADC was 78 +/- 19% higher than that in rats on a low-salt (LS) diet. The Michaelis constant (Km) of the enzyme remained unchanged. In renal cortical tubule cell suspensions the L-dopa-induced inhibition of ouabain-sensitive oxygen consumption (QO2) was significantly greater in rats on HS diet than in rats on LS diet. Furthermore, L-dopa completely inhibited the nystatin-induced rise in QO2 in the HS but not in the LS group. Carbidopa, an inhibitor of L-AADC, abolished the L-dopa-induced inhibition of nystatin-stimulated QO2 in cells from HS rats and was without significant effect in cells from LS rats. L-Dopa-stimulated K+ efflux was greater in cells from HS rats at 28 +/- 1 nmol.min-1.mg protein-1, compared with 7 +/- 6 nmol.min-1.ng protein-1 in cells from LS rats. By contrast, ouabain-stimulated K+ efflux did not differ between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

High-salt diet upregulates activity and mRNA of renal Na(+)-K(+)-ATPase in Dahl salt-sensitive rats

1993 ◽  
Vol 264 (3) ◽  
pp. F448-F452 ◽  
Author(s):  
A. Nishi ◽  
G. Celsi ◽  
A. Aperia
Keyword(s):  
Atpase Activity ◽  
Proximal Tubule ◽  
Hormonal Regulation ◽  
High Salt ◽  
Dopa Decarboxylase ◽  
Primary Defect ◽  
High Salt Diet ◽  
Salt Diet ◽  
Tubular Cells ◽  
Proximal Tubule Segments

We examined the effect of a high-salt (HS) diet on the regulation of renal cortical Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) in young Dahl salt-sensitive (DS) and salt-resistant (DR) rats. The activity of Na(+)-K(+)-ATPase, determined in permeabilized proximal tubule segments, was similar in DS and DR rats on normal salt (NS) diet. HS diet resulted in a twofold increase in proximal tubule Na(+)-K(+)-ATPase activity in DS rats but not in DR rats. The mRNA abundance, which was also similar in DS and DR rats on NS diet, increased after 2 days on HS diet in both innervated and denervated kidneys from DS rats but had no effect in DR rats. The activity of Na(+)-K(+)-ATPase and the content of alpha 1- and beta-protein in cortical homogenate were similar in DS and DR rats on both NS and HS diets. Treatment with benserazide, an inhibitor of dopa decarboxylase, upregulated proximal tubule Na(+)-K(+)-ATPase activity and increased Na(+)-K(+)-ATPase mRNA in DR rats on HS diet. Taken together, these data indicate that there is a primary defect in the dynamic hormonal regulation of Na(+)-K(+)-ATPase activity in intact tubular cells, which might stimulate Na(+)-K(+)-ATPase transcription.

Mechanism of proximal tubule bicarbonate absorption in NHE3 null mice

1999 ◽  
Vol 277 (2) ◽  
pp. F298-F302 ◽  
Author(s):  
Tong Wang ◽  
Chao-Ling Yang ◽  
Thecla Abbiati ◽  
Patrick J. Schultheis ◽  
Gary E. Shull ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Proximal Tubule ◽  
Apical Membrane ◽  
Significant Inhibition ◽  
Fluid Absorption ◽  
Wild Type ◽  
Significant Component ◽  
Nhe Isoforms

NHE3 is the predominant isoform responsible for apical membrane Na+/H+exchange in the proximal tubule. Deletion of NHE3 by gene targeting results in an NHE3−/−mouse with greatly reduced proximal tubule[Formula: see text] absorption compared with NHE3+/+ animals (P. J. Schultheis, L. L. Clarke, P. Meneton, M. L. Miller, M. Soleimani, L. R. Gawenis, T. M. Riddle, J. J. Duffy, T. Doetschman, T. Wang, G. Giebisch, P. S. Aronson, J. N. Lorenz, and G. E. Shull. Nature Genet. 19: 282–285, 1998). The purpose of the present study was to evaluate the role of other acidification mechanisms in mediating the remaining component of proximal tubule [Formula: see text] reabsorption in NHE3−/− mice. Proximal tubule transport was studied by in situ microperfusion. Net rates of[Formula: see text] ( J HCO3) and fluid absorption ( J v) were reduced by 54 and 63%, respectively, in NHE3 null mice compared with controls. Addition of 100 μM ethylisopropylamiloride (EIPA) to the luminal perfusate caused significant inhibition of J HCO3 and J v in NHE3+/+ mice but failed to inhibit J HCO3 or J v in NHE3−/− mice, indicating lack of activity of NHE2 or other EIPA-sensitive NHE isoforms in the null mice. Addition of 1 μM bafilomycin caused a similar absolute decrement in J HCO3 in wild-type and NHE3 null mice, indicating equivalent rates of[Formula: see text] absorption mediated by H+-ATPase. Addition of 10 μM Sch-28080 did not reduce J HCO3 in either wild-type or NHE3 null mice, indicating lack of detectable H+-K+-ATPase activity in the proximal tubule. We conclude that, in the absence of NHE3, neither NHE2 nor any other EIPA-sensitive NHE isoform contributes to mediating [Formula: see text] reabsorption in the proximal tubule. A significant component of[Formula: see text] reabsorption in the proximal tubule is mediated by bafilomycin-sensitive H+-ATPase, but its activity is not significantly upregulated in NHE3 null mice.

Effects of high salt intake on dopamine production in rat kidney

1991 ◽  
Vol 260 (5) ◽  
pp. E675-E679 ◽  
Author(s):  
M. Hayashi ◽  
Y. Yamaji ◽  
W. Kitajima ◽  
T. Saruta
Keyword(s):  
Degradation Rate ◽  
Salt Intake ◽  
Rat Kidney ◽  
Dopamine Metabolism ◽  
High Salt ◽  
Acid Decarboxylase ◽  
Amino Acid Decarboxylase ◽  
High Salt Intake ◽  
Urinary Dopamine ◽  
Convoluted Tubules

To examine the origin of increased urinary dopamine excretion (UDAV) during high salt intake, we measured UDAV from the innervated (INN) or the chronically denervated (DEN) kidney in rats fed either a high-salt (HS) or low-salt (LS) diet. UDAV of DEN [3.50 +/- 0.46 ng. min-1.inulin clearance (CIN)-1] and INN (4.00 +/- 0.59 ng. min-1.CIN-1) kidneys in the HS group showed a significant increase compared with that of the respective kidney in the LS group (DEN 1.42 +/- 0.12, INN 1.44 +/- 0.09 ng.min-1.CIN-1), whereas the effect of denervation on UDAV was not significantly different between two groups. We determined aromatic L-amino acid decarboxylase (L-AADC) activity and dopamine degradation rate of microdissected proximal convoluted tubules to study the changes in dopamine metabolism. L-AADC activity in the HS group showed a significant increase compared with that in the LS group, although there was no significant change in dopamine degradation rate. We conclude that the increase in UDAV during high salt intake was mainly caused by the enhancement of extraneural dopamine production by the kidney in rats. Dopamine-producing enzyme, but not its degradation in the tubular cells, plays a role in the regulation of extraneural dopamine production.

scholarly journals Influence of Human Sera on the In Vitro Activity of the Echinocandin Caspofungin (MK-0991) against Aspergillus fumigatus

2000 ◽  
Vol 44 (12) ◽  
pp. 3302-3305 ◽  
Author(s):  
Tom Chiller ◽  
Kouros Farrokhshad ◽  
Elmer Brummer ◽  
David A. Stevens
Keyword(s):  
Aspergillus Fumigatus ◽  
Human Serum ◽  
Hyphal Growth ◽  
Significant Inhibition ◽  
Dependent Inhibition ◽  
Human Sera ◽  
Dose Dependent Inhibition ◽  
Synthase Inhibitor ◽  
Dose Dependent

ABSTRACT There have been several reports that the activity of echinocandin antifungal agents is not affected or decreased in the presence of human sera. It is known that these drugs are bound >80% in animal and human sera. The activity of the echinocandin caspofungin (MK-0991), a 1,3-β-d-glucan synthase inhibitor, againstAspergillus fumigatus with and without human sera was studied. Conidia of A. fumigatus in microtest plate wells formed germlings after overnight culture in RPMI 1640. Caspofungin was then added with or without serum, and the germlings were incubated at 37°C for 24 h. Human serum (5%) in RPMI 1640 alone did not significantly inhibit the growth of A. fumigatus in vitro. Caspofungin in RPMI 1640 exhibited dose-dependent inhibition, with concentrations of 0.1 and 0.05 μg/ml inhibiting 24.9% +/− 10.4% and 11.7% +/− 3.6%, respectively (n = 10;P < 0.01). The addition of 5% human serum to caspofungin at 0.1 or 0.05 μg/ml increased the inhibition to 78.6% +/− 5.8% or 58.3% +/− 19.2%, respectively (n = 10; P < 0.01 versus controls and versus the drug without serum). Lower concentrations of serum also potentiated drug activity. The effect of human sera was further seen when using caspofungin that had lost activity (e.g., by storage) against A. fumigatus at 0.1 μg/ml. Inactive caspofungin alone demonstrated no significant inhibition of hyphal growth, whereas the addition of 5% human serum to the inactive drug showed 83% +/− 16.5% inhibition (n = 5; P < 0.01). The restoration of activity of caspofungin was seen at concentrations as low as 0.05% human serum. In contrast to prior reports, this study suggests that human serum acts synergistically with caspofungin to enhance its inhibitory activity in vitro against A. fumigatus.

scholarly journals Antinociceptive Activity of Ethanol Extract fromDuguetia chrysocarpaMaas (Annonaceae)

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Jackson Roberto Guedes da Silva Almeida ◽  
Edigênia Cavalcante da Cruz Araújo ◽  
Luciano Augusto de Araújo Ribeiro ◽  
Julianeli Tolentino de Lima ◽  
Xirley Pereira Nunes ◽  
...  
Keyword(s):  
Antinociceptive Effect ◽  
Intraperitoneal Administration ◽  
Ethanol Extract ◽  
Significant Inhibition ◽  
Antinociceptive Activity ◽  
Hot Plate Test ◽  
Phytochemical Investigation ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition ◽  
First Time

The ethanol extract from the fruits ofDuguetia chrysocarpawas evaluated for its antinociceptive activity in chemical and thermal models of nociception in mice. The intraperitoneal administration of the ethanol extract (100, 200, and 400 mg/kg body weight) showed a dose-dependent inhibition of acetic-acid-induced abdominal writhes. The extract also produced a significant inhibition of both phases of the formalin test in all doses tested and increased the reaction time in hot-plate test at dose of 200 mg/kg. The data obtained suggest that the antinociceptive effect of the extract may be mediated via both peripheral and central mechanisms. The phytochemical investigation yielded the isolation of the benzenoid derivative 3-methoxy-4-ethoxy benzoic acid which is being reported for the first time in this genus.

Inhibition of rat mesangial cell growth by heparan sulfate

1990 ◽  
Vol 258 (2) ◽  
pp. F259-F265
Author(s):  
G. C. Groggel ◽  
G. N. Marinides ◽  
P. Hovingh ◽  
E. Hammond ◽  
A. Linker
Keyword(s):  
Cell Growth ◽  
Heparan Sulfate ◽  
Mesangial Cell ◽  
Mesangial Cells ◽  
Significant Inhibition ◽  
3T3 Fibroblasts ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition ◽  
Dose Dependent ◽  
Endogenous Component

The ability of heparan sulfate, an endogenous component of the glomerulus, to regulate the growth of cultured rat mesangial cells was investigated. Heparan sulfate caused a dose-dependent inhibition of rat mesangial cell growth, 85% inhibition compared with controls at the highest dose (1,000 micrograms/ml). Chondroitin sulfate produced no inhibition. The low-sulfated fraction of heparan sulfate (9%) produced more inhibition than the high-sulfated fraction (13%), 90 +/- 1 vs. 71 +/- 2% (P = 0.002). The effects of the heparan sulfate were completely reversible. Treatment of heparan sulfate with heparitinase increased the degree of inhibition, 71 +/- 1 vs. 84 +/- 1% (P less than 0.001). Four different oligosaccharides derived from heparan sulfate and heparin were tested for their ability to inhibit growth. One of the oligosaccharides, low-sulfated (10%), caused significant inhibition, 76 +/- 2%. Heparan sulfate was also able to inhibit the growth of Swiss 3T3 fibroblasts (63 +/- 5%). This inhibition was less marked than that seen with mesangial cells. Thus heparan sulfate was able to significantly inhibit rat mesangial cell growth in culture. Alterations in glomerular heparan sulfate may play an important role in alterations in mesangial cell growth.

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