Dual effect of polyphenolic compounds on cardiac Na+/K+-ATPase during development and persistence of hypertension in ratsThis article is one of a selection of papers published in a special issue on Advances in Cardiovascular Research.

The enzyme kinetics of cardiac Na+/K+-ATPase were used for characterizing the ATP- and Na+-binding sites after administration of red wine polyphenolic compounds (Provinol) during developing and sustained hypertension. Hypertension was induced in rats (LN group) by the nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME, 40 mg·kg–1·day–1). Provinol (40 mg·kg–1·day–1) was applied during developing hypertension (LNPF4 group) and sustained hypertension (LNPF7/3 group). Provinol reduced the number of active Na+/K+-ATPase molecules in cardiac tissue, as indicated by decreased Vmax values (by 33% in LNPF4 and 26% in LNPF7/3 compared with LN). Concerning qualitative properties of the enzyme, Provinol induced different effects on the ATP- and Na+-binding sites of Na+/K+-ATPase. The ATP-binding site was impaired by Provinol, as indicated by increased Km value (by 52% in LNPF4 vs. LN), suggesting worsened utilization of substrate by the enzyme. In sustained hypertension, however, Provinol had no..., On a utilisé la cinétique enzymatique de la Na+/K+-ATPase pour caractériser les sites de liaison de l’ATP et du Na+ après l’administration de composés polyphénoliques du vin rouge (Provinol) durant l’installation de l’hypertension et l’hypertension confirmée. On a induit l’hypertension chez des rats (groupe LN) par le biais de l’inhibiteur de la monoxyde d’azote synthase, l-NAME (40 mg·kg–1·jour–1). On a administré le Provinol (40 mg·kg–1·jour–1) durant l’installation de l’hypertension (LNPF4) et durant l’hypertension confirmée (LNPF7/3). Le Provinol a réduit le nombre de molécules actives de la Na+/K+-ATPase dans le tissu cardiaque, comme l’indique la diminution des valeurs de Vmax (de 33 % chez LNPF4 et de 26 % chez LNPF7/3 comparativement à celles du groupe LN). Du point de vue qualitatif, le Provinol a induit divers effets sur les sites de liaison de l’ATP et du Na+ de la Na+/K+-ATPase. Il a altéré le site de liaison de l’ATP, comme le montre l’augmentation de la valeur de Km (de 52 % chez le groupe L..

Effect of the Pyridoindole Antioxidant Stobadine on the Cardiac Na + ,K + -ATPase in Rats with Streptozotocin-Induced Diabetes

Abstract. In the present study we examined the effect of dietary supplementation with the pyridoindole antioxidant stobadine on functional properties of the cardiac Na + ,K + -ATPase in diabetic rats. Diabetes lasting sixteen weeks which was induced by a single i.v. dose of streptozotocin (55 mg·kg −1 ) was followed by decrease in the enzyme activity. Evaluation of kinetic parameters revealed a statistically significant decrease in the maximum velocity (V max ) (32 % for ATP-activation, 33 % for Na + -activation), indicating a diabetes-induced diminution of the number of active enzyme molecules in cardiac sarcolemma. The ATP-binding properties of the enzyme were not affected by diabetes as suggested by statistically insignificant changes in the value of Michaelis-Menten constant, K M(ATP) . On the other hand, the affinity to sodium decreased as suggested by 54 % increase in the K M(Na + ) value. This impairment in the affinity of the Na + -binding site together with decreased number of active Na + ,K + -ATPase molecules are probably responsible for the deteriorated enzyme function in hearts of diabetic animals. Administration of stobadine to diabetic rats dramatically improved the function of cardiac Na + ,K + -ATPase with regard to Na + -handling, as documented by statistically significant elevation of V max by 66 and 47 % decrease in K M(Na + ) . Our data suggest that stobadine may prevent the diabetes-induced deterioration of cardiac Na + ,K + -ATPase, thus enabling to preserve its normal function in regulation of intracellular homeostasis of Na + and K + ions

Quantitative Relationship Between the Protein Secondary Structure in Cardiac Sarcolemma and the Activity of the Membrane-bound Ca 2+ -ATPase

Abstract. In the absence of ATP, increasing concentrations of calcium within a range between 0.1-8.0 mmol. I" 1 gradually lowered the a-helix content of proteins in rat heart sarcolemma requiring no energy supply. In the presence of ATP, similar concentrations of calcium stepwise activated the sarcolemmal low-affinity Ca 2+ -ATPase. A mathematical analysis of the data obtained revealed a quantitative relationship between calcium-induced stimulation of the Ca 2+ -ATPase activity and a diminution of the a-helix contents of membrane proteins in cardiac sarcolemma. The cooperation between changes in protein conformation and energy consumption in relation to the supposed role of low-affinity Ca 2+ -ATPase in gating the calcium channel are discussed

Effect of saliva from horse fly Hybomitra bimaculata on kinetic properties of Na,K-ATPase: possible role in regulation of relaxation

The possible involvement of salivary gland extract (SGE) from horse flies in modifying hyperpolarization and relaxation via alterations in functional properties of sarcolemmal Na,K-ATPase in the host tissue was tested in vitro by application of various amounts of SGE from Hybomitra bimaculata

Na,K-ATPase Kinetics and Oxidative Stress in Kidneys of Zucker Diabetic Fatty (fa/fa) Rats Depending on the Diabetes Severity—Comparison with Lean (fa/+) and Wistar Rats

For a better insight into relations between type 2 diabetes mellitus (T2DM) and Na,K-ATPase properties in kidneys, we aimed to characterize two subgroups of ZDF obese (fa/fa) rats, with more and less developed T2DM, and compare them with two controls: lean (fa/+) and Wistar. Na,K-ATPase enzyme kinetics were estimated by measuring the ATP hydrolysis in the range of NaCl and ATP levels. As Na,K-ATPase is sensitive to oxidative stress, we evaluated selected oxidative stress parameters in kidney homogenates. Our results suggest that thiol–disulfide redox balance in the renal medulla and Na,K-ATPase properties in the renal cortex differ between both controls, while observed measurements in lean (fa/+) rats showed deviation towards the values observed in ZDF (fa/fa) rats. In comparison with both controls, Na,K-ATPase enzyme activity was higher in the renal cortex of ZDF rats independent of diabetes severity. This might be a consequence of increased glucose load in tubular fluid. The increase in lipid peroxidation observed in the renal cortex of ZDF rats was not associated with Na,K-ATPase activity impairment. Regarding the differences between subgroups of ZDF animals, well-developed T2DM (glycemia higher than 10 mmol/L) was associated with a higher ability of Na,K-ATPase to utilize the ATP energy substrate

Erythrocyte Deformability and Na,K-ATPase Activity in Various Pathophysiological Situations and Their Protection by Selected Nutritional Antioxidants in Humans

The physicochemical and functional properties of erythrocytes are worsened in a variety of diseases. Erythrocyte deformability refers to their ability to adjust their shape according to external forces exerted against them in the circulation. It is influenced by the functionality of the Na,K-ATPase enzyme, which is localized in their membranes. The proposed review is focused on knowledge regarding changes in erythrocyte Na,K-ATPase activity, and their impact on erythrocyte deformability in various pathophysiological situations observed exclusively in human studies, as well as on the potential erytroprotective effects of selected natural nutritional antioxidants. A clear link between the erythrocyte properties and the parameters of oxidative stress was observed. The undesirable consequences of oxidative stress on erythrocyte quality and hemorheology could be at least partially prevented by intake of diverse antioxidants occurring naturally in foodstuffs. Despite intensive research concerning the effect of antioxidants, only a small number of investigations on erythrocyte properties in humans is available in databases. It is worth shifting attention from animal and in vitro experiments and focusing more on antioxidant administration in human studies in order to establish what type of antioxidant, in what concentration, and in which individuals it may provide a beneficial effect on the human organism, by protecting erythrocyte properties