Due to the importance of renal Na,K-ATPase in maintaining the sodium homeostasis in the organism, its activity and abundance is intensively studied in condition of diabetes mellitus. The main subject of this study was the investigation of properties of renal Na,K-ATPase and abundance of its α1 subunit in view of possible gender-dependent differences in male and female diabetic rats. Diabetes was induced by a single intraperitoneal dose of streptozotocin in a dose of 65 mg•kg-1. The acute diabetes lasting 8 days induced a significant increase in Na,K-ATPase activity accompanied by significant gender specific increase in K m value indicating a worsened affinity of ATP-binding site in female rats. In addition, our present experiments, revealed a significantly higher abundance of renal Na,K-ATPase α1 subunit in diabetic rats of both genders amounting 94% increase in males and 107% in females. But, not all of the newly synthesized enzyme molecules are fully active, as the increase in the number of active molecules is smaller (representing 23% in males and 20% in females) as indicated by lower increase in V max values.

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It is commonly known that consumption of foods and beverages rich in polyphenols is associated with a lower incidence of cardiovascular disease. The purpose of this study was to assess whether the application of red wine polyphenols influences the kinetic properties of renal Na+,K+‐ATPase in rats in which hypertension has been experimentally induced by the nitric oxide synthase inhibitor L‐NAME. Treatment with polyphenols during the recovery from hypertension to normotension resulted in the complete revival of the functional properties of the Na+,K+‐ATPase, as indicated by the total restoration of Km, KNa (concentration of Na+ necessary to achieve half‐maximal reaction velocity) and Vmax for enzyme activation by ATP and/or Na+ to pre‐hypertension values. Two positive effects of polyphenols during the recovery period are indicated: a restoration of the affinity of the ATP and Na+ binding sites to control values and a probable increase in the number of Na+,K+‐ATPase molecules to a level comparable to that in control conditions, as suggested by the complete renewal of Vmax.

Abstract. For characterization of Na + ,K + -ATPase, a key enzyme involved in maintenance of intracellular sodium homeostasis, expression of α1 subunit and the ATP-and Na + -binding properties were investigated by Western blot analysis and by enzyme kinetics, respectively. Previous studies documented time-dependent alteration of properties of renal Na + ,K + -ATPase from its mobilization after 8 days to serious deteriorations after 16 weeks of diabetes in rats. Characterizing the critical period during development of the disease, when mobilization of Na + ,K + -ATPase observed in the acute phase turns to its damage, we examined the enzyme properties after 8 weeks lasting diabetes which was induced by a single intraperitoneal administration of streptozotocin in a dose of 65 mg·kg -1 . The unchanged expression of Na + ,K + -ATPase α1-subunit in both genders indicates that 8 weeks represent the time when the mobilization of enzyme synthesis observed previously in acute diabetes is lost. In this time the renal Na + ,K + -ATPase undergoes structural changes in the vicinity of Na + -binding site resulting in worsened affinity to sodium in both genders as indicated by 13% and 18% increase of K Na value in female and male rats, respectively. However, gender specific was the diabetes-induced decrease in affinity to ATP by 18% which occurred in female rats only.

It has been suggested that polyphenolic substances provide protection against the risk factors of cardiovascular diseases. The present study was designed to investigate whether application of red wine polyphenols influences the kinetic properties of the renal Na + ,K + -ATPase in rats with hypertension (164 ± 8 mmHg) that was experimentally induced by the NO synthase inhibitor N G. -nitro-L-arginine methyl ester (L-NAME). Polyphenols in a dose of 40 mg kg −1 day −1 in drinking fluid induced different effects on the properties of the renal Na + ,K + -ATPase depending on the mode of their administration. Preventive application of polyphenols during the development of hypertension (144 ± 5 mmHg) partially protected the Na + ,K + -ATPase molecule against hypertension-induced deterioration via increased capability of the enzyme to bind ATP and/or Na + as suggested by decrease of K m and K Na , respectively, even to values lower than in controls. However, polyphenols did not prevent the hypertension-induced reduction of the number of active Na + ,K + -ATPase molecules as shown by similar V max values as compared to the hypertensive L-NAME group. The above protection is probably secured by a NO-dependent mechanism as suggested by 150% increase of the NO synthesis. Additional treatment of already hypertensive animals with polyphenols (153 ± 8 mmHg) resulted in partial restoration of the Na + ,K + -ATPase affinities especially for sodium as indicated by significant diminution of K Na . However, polyphenols in this mode of application did not slow down the L-NAME-induced decrease in the number of Na + ,K + -ATPase molecules in the kidney as suggested by additional significant decrease in V max values when comparing this group with the control group and also the hypertensive L-NAME group. In this case the polyphenols affected the Na,K-ATPase molecule in a NO-independent way as indicated by the fact that polyphenols failed to restore normal NO synthesis.