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Nitric oxide - superoxide cooperation in the regulation of renal Na+,K+-ATPase.

100%
Bełtowski J., Marciniak A., Jamroz-Wiśniewska A., Borkowska E.
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vol. 51
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issue 4
933-942
EN
The aim of this study was to investigate whether endogenous superoxide anion is involved in the regulation of renal Na+,K+-ATPase and ouabain-sensitive H+,K+-ATPase activities. The study was performed in male Wistar rats. Compounds modulating superoxide anion concentration were infused under general anaesthesia into the abdominal aorta proximally to the renal arteries. The activity of ATPases was assayed in isolated microsomal fraction. We found that infusion of a superoxide anion-generating mixture, xanthine oxidase (1 mU/min per kg) + hypoxanthine (0.2 μmol/min per kg), increased the medullary Na+,K+-ATPase activity by 49.5% but had no effect on cortical Na+,K+-ATPase and either cortical or medullary ouabain-sensitive H+,K+-ATPase. This effect was reproduced by elevating endogenous superoxide anion with a superoxide dismutase inhibitor, diethylthiocarbamate. In contrast, a superoxide dismutase mimetic, TEMPOL, decreased the medullary Na+,K+-ATPase activity. The inhibitory effect of TEMPOL was abolished by inhibitors of nitric oxide synthase (L-NAME), soluble guanylate cyclase (ODQ) and protein kinase G (KT5823). The stimulatory effect of diethylthiocarbamate was not observed in animals pretreated with a synthetic cGMP analogue, 8-bromo-cGMP. An inhibitor of NAD(P)H oxidase, apocynin (1 μmol/min per kg), decreased the Na+,K+-ATPase activity in the renal medulla and its effect was prevented by L-NAME, ODQ or KT5823. In contrast, a xanthine oxidase inhibitor, oxypurinol, administered at the same dose was without effect. These data suggest that NAD(P)H oxidase-derived superoxide anion increases Na+,K+-ATPase activity in the renal medulla by reducing the availability of NO. Excessive intrarenal generation of superoxide anion may upregulate medullary Na+,K+-ATPase leading to sodium retention and blood pressure elevation.
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Regulation of renal Na+,K+ -ATPase and ouabain-sensitive H+,K+ -ATPase by the cyclic AMP-protein kinase A signal transduction pathway.

100%
Bełtowski J., Marciniak A., Wójcicka G., Górny D.
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2003
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vol. 50
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issue 1
103-114
EN
We investigated the effect of the cyclic AMP-protein kinase A (PKA) signalling pathway on renal Na+,K+-ATPase and ouabain-sensitive H+,K+-ATPase. Male Wistar rats were anaesthetized and catheter was inserted through the femoral artery into the abdominal aorta proximally to the renal arteries for infusion of the investigated substances. Na+,K+-ATPase activity was measured in the presence of Sch 28080 to block ouabain-sensitive H+,K+-ATPase and improve specificity of the assay. Dibutyryl-cyclic AMP (db-cAMP) administered at a dose of 10-17 mol/kg per min and 10-6 mol/kg per min increased Na+,K+-ATPase activity in the renal cortex by 34% and 42%, respectively, and decreased it in the renal medulla by 30% and 44%, respectively. db-cAMP infused at 10-6 mol/kg per min increased the activity of cortical ouabain-sensitive H+,K+-ATPase by 33%, and medullary ouabain-sensitive H+,K+-ATPase by 30%. All the effects of db-cAMP were abolished by a specific inhibitor of protein kinase A, KT 5720. The stimulatory effect on ouabain-sensitive H+,K+-ATPase and on cortical Na+,K+-ATPase was also abolished by brefeldin A which inhibits the insertion of proteins into the plasma membranes, whereas the inhibitory effect on medullary Na+,K+-ATPase was partially attenuated by 17-octadecynoic acid, an inhibitor of cytochrome P450-dependent arachidonate metabolism. We conclude that the cAMP-PKA pathway stimulates Na+,K+-ATPase in the renal cortex as well as ouabain-sensitive H+,K+-ATPase in the cortex and medulla by a mechanism requiring insertion of proteins into the plasma membrane. In contrast, medullary Na+,K+-ATPase is inhibited by cAMP through a mechanism involving cytochrome P450-dependent arachidonate metabolites.
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Time-dependent effect of leptin on renal Na+,K+-ATPase activity

100%
Marciniak A., Jamroz-Wiśniewska A., Borkowska E., Bełtowski J.
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2005
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vol. 52
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issue 4
803-809
EN
Leptin, secreted by adipose tissue, is involved in the pathogenesis of arterial hypertension, however, the mechanisms through which leptin increases blood pressure are incompletely elucidated. We investigated the effect of leptin, administered for different time periods, on renal Na+,K+-ATPase activity in the rat. Leptin was infused under anesthesia into the abdominal aorta proximally to the renal arteries for 0.5-3 h. Leptin administered at doses of 1 and 10 µg/min per kg for 30 min decreased the Na+,K+-ATPase activity in the renal medulla. This effect disappeared when the hormone was infused for ≥1 h. Leptin infused for 3 h increased the Na+,K+-ATPase activity in the renal cortex and medulla. The stimulatory effect was abolished by a specific inhibitor of Janus kinases (JAKs), tyrphostin AG490, as well as by an NAD(P)H oxidase inhibitor, apocynin. Leptin increased urinary excretion of hydrogen peroxide (H2O2) between 2 and 3 h of infusion. The effect of leptin on renal Na+,K+-ATPase and urinary H2O2 was augmented by a superoxide dismutase mimetic, tempol, and was abolished by catalase. In addition, infusion of H2O2 for 30 min increased the Na+,K+-ATPase activity. Inhibitors of extracellular signal regulated kinases (ERKs), PD98059 or U0126, prevented Na+,K+-ATPase stimulation by leptin and H2O2. These data indicate that leptin, by acting directly within the kidney, has a delayed stimulatory effect on Na+,K+-ATPase, mediated by JAKs, H2O2 and ERKs. This mechanism may contribute to the abnormal renal Na+ handling in diseases associated with chronic hyperleptinemia such as diabetes and obesity.
4
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Species- and substrate-specific stimulation of human plasma paraoxonase 1 (PON1) activity by high chloride concentration.

100%
Bełtowski J., Wójcicka G., Marciniak A.
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2002
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vol. 49
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issue 4
927-936
EN
Paraoxonase 1 (PON1), contained in plasma high-density lipoproteins, plays an important role in the protection of plasma lipoproteins and cell membranes from oxidative damage. Previous studies indicate that human PON1 is stimulated by high NaCl concentrations. The aim of this study was to characterize in more detail the effect of salts on serum PON1. Paraoxon-hydrolyzing activity of human serum was stimulated by 81.6% following the addition of 1 M NaCl. The effect of NaCl was dose-dependent between 0.5 and 2 M. PON1 activity toward phenyl acetate was reduced by 1 M NaCl by 55.2%. Both the paraoxon- and phenyl acetate-hydrolysing activity was slightly lower in heparinized plasma than in serum, but NaCl had similar stimulatory and inhibitory effects on these activities, respectively. In rat, rabbit, and mouse, NaCl reduced PON1 activity. KCl had a similar effect on human PON1 as NaCl. Sodium nitrite also stimulated human PON1 but much less effectively than chloride salts. In contrast, sucrose, sodium acetate and sodium lactate had no significant effect. NaBr was a less effective PON1 activator than NaCl, whereas the effect of NaJ was non-significant. The activity of human PON1 toward homogentisic acid lactone and γ-decanolactone was unaltered by NaCl. These data indicate that: 1) high concentrations of chlorides stimulate human PON1 activity toward paraoxon but not other substrates, 2) PON1 is inhibited by Cl- in other mammalian species, 3) the potency of human PON1 activation by halogene salts increases with decreasing atomic mass of the halide anion.
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Bidirectional regulation of renal cortical Na+,K+-ATPase by protein kinase C.

88%
Bełtowski J., Marciniak A., Jamroz-Wiśniewska A., Borkowska E., Wójcicka G.
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vol. 51
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issue 3
757-772
EN
We examined the role of protein kinase C (PKC) in the regulation of Na+,K+- ATPase activity in the renal cortex. Male Wistar rats were anaesthetized and the investigated reagents were infused into the abdominal aorta proximally to the renal arteries. A PKC-activating phorbol ester, phorbol 12,13-dibutyrate (PDBu), had a dose-dependent effect on cortical Na+,K+-ATPase activity. Low dose of PDBu (10-11 mol/kg per min) increased cortical Na+,K+-ATPase activity by 34.2%, whereas high doses (10-9 and 10-8 mol/kg per min) reduced this activity by 22.7% and 35.0%, respectively. PDBu administration caused changes in Na+,K+-ATPase Vmax without affecting K0.5 for Na+, K+ and ATP as well as Ki for ouabain. The effects of PDBu were abolished by PKC inhibitors, staurosporine, GF109203X, and Gö 6976. The inhibitory effect of PDBu was reversed by pretreatment with inhibitors of cytochrome P450-dependent arachidonate metabolism, ethoxyresorufin and 17-octadecynoic acid, inhibitors of phosphatidylinositol 3-kinase (PI3K), wortmannin and LY294002, and by actin depolymerizing agents, cytochalasin D and latrunculin B. These results suggest that PKC may either stimulate or inhibit renal cortical Na+,K+-ATPase. The inhibitory effect is mediated by cytochrome P450-dependent arachidonate metabolites and PI3K, and is caused by redistribution of the sodium pump from the plasma membrane to the inactive intracellular pool.
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