Sex-specific response of renal Na,K-ATPase to prenatal angiotensin 2 exposure and increased salt intake in offspring.

In rodents, increased angiotensin 2 (Ang2) during pregnancy increases blood pressure and decreases salt sensitivity in the offspring. To explore the underlying mechanisms, this study evaluated the effects of prenatal Ang2 exposure on the activity of renal Na,K-ATPase, which is one of the main systems that maintains sodium ion homeostasis in an organism. Moreover, this study also investigated the impact of a higher-salt diet on the enzyme activity in the offspring in a sex-dependent manner. Pregnant Wistar rats were implanted with osmotic minipumps that continuously released Ang2 (2 µg/kg/h) for 2 weeks. Male and female offspring of treated and control females were allocated to groups fed with normal or high-salt diets. In the offspring prenatally treated with Ang2, a significant Vmax increase (23 - 36%) was observed in females fed with both a normal and high-salt diet. In addition, a significant increase in Km (20 - 26%) was also observed in the female groups, compared to respective male groups, independently of their diet. Evaluation of KNa showed significantly lower values (13 - 17%) in female offspring fed with a high-salt diet, independent of the prenatal treatment. In conclusion, these data suggest that increased prenatal Ang2 has a predominant impact on the properties of renal Na,K-ATPase in both sexes. Moreover, the enzyme is resistant to higher salt intake in offspring prenatally exposed to Ang2.

Properties of Na,K-ATPase in cerebellum of male and female rats: effects of acute and prolonged diabetes.

The present study was oriented to gender specificity of Na,K-ATPase in cerebellum, the crucial enzyme maintaining the intracellular homeostasis of Na ions in healthy and diabetic Wistar rats. The effects of diabetes on properties of the Na,K-ATPase in cerebellum derived from normal and streptozotocin (STZ)-diabetic rats of both genders were investigated. The samples were excised at different time intervals of diabetes induced by STZ (65 mg kg-1) for 8 days and 16 weeks. In acute 8-day-lasting model of diabetes, Western blot analysis showed significant depression of α1 isoform of Na,K-ATPase in males only. On the other hand, concerning the activity, the enzyme seems to be resistant to the acute model of diabetes in both genders. Prolongation of diabetes to 16 weeks was followed by increasing the number of active molecules of Na,K-ATPase exclusively in females as indicated by enzyme kinetic studies. Gender specificity was observed also in nondiabetic animals revealing higher Na,K-ATPase activity in control males probably caused by higher number of active enzyme molecules as indicated by increased value of V max when comparing to control female group. This difference seems to be age dependent: at the age of 16 weeks, the V max value in females was higher by more than 90%, whereas at the age of 24 weeks, this difference amounted to only 28%. These data indicate that the properties of Na,K-ATPase in cerebellum, playing crucial role in maintaining the Na+ and K+ gradients, depend on gender, age, and duration of diabetic impact.

Effect of yeast biomass with high content of carotenoids on erythrocyte deformability, NO production and Na,K-ATPase activity in healthy and LPS treated rats.

Measurements of red blood cell (RBC) deformability together with estimation of NO-synthase activity and Na,K-ATPase activity were used for characterization of RBC functionality in rats subjected to single dose of Escherichia coli lipopolysaccharides (LPS) at a dose of 1 mg/kg. We hypothesized that LPS might initiate a malfunction of RBC. We also investigated the potential effect of carotenoids (10 mg/kg/day) produced in red yeast biomass of Rhodotorula glutinis on RBC in LPS-challenged rats. LPS significantly reduced the deformability of RBC (by 14%) together with decrease of NO-synthase activity by 20%. Daily supplementation of carotenoids for 10 days attenuated the LPS-induced injury, as observed by 22% increase of RBC deformability and 23% increase of NO-synthase activity. The activity of Na,K-ATPase was also improved probably due to increased number of active enzyme molecules as indicated by 66% enhancement of Vmax value, hence maintaining the activity of erythrocyte Na,K-ATPase to the level even higher as compared with healthy control animals. It may be concluded that administration of yeast biomass with high content of carotenoids resulted in advanced function of erythrocytes as concerns their ability to squeeze through narrow capillaries of the circulation, better intrinsic production of NO and improvement of intracellular homeostasis of sodium.

Effect of duration of diabetes mellitus type 1 on properties of Na, K-ATPase in cerebral cortex.

Time sequence study was performed to characterize the effects of diabetes mellitus type 1 on properties of the Na, K-ATPase in cerebral cortex derived from normal and streptozotocin (STZ)-diabetic rats of both genders. The samples were excised at varying time intervals of diabetes induced by STZ (65 mg kg(-1)) for 8 days, and 8 and 16 weeks. Expression of α1-3 isoforms of Na, K-ATPase was not altered in statistically significant level during all stages of diabetes neither in female nor in male rats as revealed from Western blot analysis. Studies of kinetic properties of the enzyme resulted in variations in active number of Na, K-ATPase molecules as well as its qualitative properties. Sixteen-week-old control male rats showed better affinity to substrate as indicated by 13 % decrease of K m value. The effect persisted also in males subjected to 8 days lasting diabetes; however, in males subjected to 8 weeks lasting diabetes, the effect was lost. In 25-week-old rats, the Na, K-ATPase revealed again altered properties in males and females but the mechanism of the variation was different. In females, the number of active molecules of Na, K-ATPase was higher by 32 % in controls and by 17 % in rats with chronic diabetes when comparing to respective male groups as suggested by increased value of V max. So the properties of Na, K-ATPase in cerebral cortex, playing crucial role in maintaining intracellular homeostasis of Na(+) ions, depend on gender, age, and duration of diabetic insult.

Effects of γ-irradiation on Na,K-ATPase in cardiac sarcolemma.

Previous studies showed that adverse effect of ionizing radiation on the cardiovascular system is beside other factors mostly mediated by reactive oxygen and nitrogen species, which deplete antioxidant stores. One of the structures highly sensitive to radicals is the Na,K-ATPase the main system responsible for extrusion of superfluous Na(+) out of the cell which utilizes the energy derived from ATP. The aim of present study was the investigation of functional properties of cardiac Na,K-ATPase in 20-week-old male rats 6 weeks after γ-irradiation by a dose 25 Gy (IR). Irradiation induced decrease of systolic blood pressure from 133 in controls to 85 mmHg in IR group together with hypertrophy of right ventricle (RV) and hypotrophy of left ventricle (LV). When activating the cardiac Na,K-ATPase with substrate, its activity was lower in IR in the whole concentration range of ATP. Evaluation of kinetic parameters revealed a decrease of the maximum velocity (V max) by 40 % with no changes in the value of Michaelis-Menten constant (K m). During activation with Na(+), we observed a decrease of the enzyme activity in hearts from IR at all tested Na(+) concentrations. The value of V max decreased by 38 %, and the concentration of Na(+) that gives half maximal reaction velocity (K Na) increased by 62 %. This impairment in the affinity of the Na(+)-binding site together with decreased number of active Na,K-ATPase molecules, as indicated by lowered V max values, are probably responsible for the deteriorated efflux of the excessive Na(+) from the intracellular space in hearts of irradiated rats.

Gender specific influence of fish oil or atorvastatin on functional properties of renal Na,K-ATPase in healthy Wistar and hypertriglyceridemic rats.

For better understanding of pathophysiological processes leading to increased retention of sodium as a consequence of hyperlipidemia, the properties of renal Na,K-ATPase, a key enzyme involved in maintaining sodium homeostasis in the organism, were studied. Enzyme kinetics of renal Na,K-ATPase were used for characterization of ATP- and Na(+)-binding sites after administration of fish oil (FO) (30 mg·day(-1)) or atorvastatin (0.5 mg·100 g(-1)·day(-1)) to healthy Wistar rats and rats with hereditary hypertriglyceridemia of both genders. Untreated healthy Wistar and also hypertriglyceridemic female rats revealed higher Na,K-ATPase activity as compared to respective untreated male groups. Hypertriglyceridemia itself was accompanied with higher Na,K-ATPase activity in both genders. Fish oil improved the enzyme affinity to ATP and Na(+), as indicated by lowered values of K(m) and K(Na) in Wistar female rats. In Wistar male rats FO deteriorated the enzyme in the vicinity of the Na(+)-binding site as revealed from the increased K(Na) value. In hypertriglyceridemic rats FO induced a significant effect only in females in the vicinity of the sodium binding sites resulting in improved affinity as documented by the lower value of K(Na). Atorvastatin aggravated the properties of Na,K-ATPase in both genders of Wistar rats. In hypertriglyceridemic rats protection of Na,K-ATPase was observed, but this effect was bound to females only. Both treatments protected renal Na,K-ATPase in a gender specific mode, resulting probably in improved extrusion of excessive intracellular sodium out of the cell affecting thus the retention of sodium in hHTG females only.

Effect of quercetin on kinetic properties of renal Na,K-ATPase in normotensive and hypertensive rats.

The effect of quercetin, a plant-derived bioflavonoid with documented positive effect on the cardiovascular system, was examined after 4-week supplementation in the dose of 20 mg kg(-1) x day(-1) to young male normotensive control (C) and to spontaneously hypertensive rats (SHR) over the period of their 5(th)-8(th) week of age. The study was focused on the influence of quercetin on properties of the renal Na,K-ATPase, a key system in maintaining the homeostasis of sodium in the organism. Spontaneous hypertension by itself enhanced the activity of Na,K-ATPase probably as a consequence of a higher number of active enzyme molecules, as suggested by the 15% increase of V(max), along with improved affinity to ATP, as indicated by the 30% decrease in the value of Michaelis-Menten constant K(m) in untreated SHR vs. untreated normotensive rats. Quercetin induced a decrease of Na,K-ATPase activity in the presence of all ATP and Na(+) concentrations investigated. Evaluation of kinetic parameters resulted in a constant V(max) value. The ATP-binding properties of the enzyme were not influenced by quercetin, as suggested by statistically insignificant changes in the value of K(m) both in controls and in SHR. On the other hand, the affinity to sodium decreased, as suggested by an increase in the K(Na) value by 22% and 31% in normotensive and hypertensive groups, respectively. This impairment in the affinity of the Na(+)-binding site of Na,K-ATPase molecules was probably responsible for the deteriorated enzyme function in the kidneys of quercetin treated animals.

Relationship between structure and antioxidative properties of some 3-formylchromone derivatives.

Flavonoids, which generally exhibit very good antioxidant properties, contain the chromone unity. The work elucidates the relation between chemical structure of chromones and their ability to scavenge DPPH radicals. The work deals with antioxidative properties of some hydroxy derivatives of 3-formylchromones (without substituent, 6-hydroxy-, 7-hydroxy-, 7,8-dihydroxy-). It was found that the last two derivatives scavenge DPPH radicals, whereas the first two ones do not. It was demonstrated that the presence and location of hydroxyl groups play a crucial role for antioxidative activity of 3-formylchromones. The scavenging of DPPH radicals runs through H(+) abstraction from hydroxyl groups of formylchromones. The DPPH scavenging by 3-formylchromones with hydroxyl group in the 7th position is connected with the formation of more stable form of anion than in the case of 6-hydroxy-3-formylchromone. Calculation heats of formations of studied formylchromone anions confirmed this fact. All studied 3-formylchromones did not scavenge HO( ) radicals, what supports H(+) abstraction mechanism of DPPH scavenging.

Regulatory role of nitric oxide on the cardiac Na, K-ATPase in hypertension.

The present study was focused on regulatory role of nitric oxide on functional properties of the cardiac Na, K-ATPase in three various animal models of hypertension: spontaneously hypertensive male rats (SHR) with increased activity of nitric oxide synthase (NOS) by 60 % (Sh1), SHR with decreased activity of NOS by 40 % (Sh2) and rats with hypertension induced by L-NAME (40 mg/kg/day) with depressed activity of NOS by 72 % (LN). Studying the utilization of energy substrate we observed higher Na, K-ATPase activity in the whole concentration range of ATP in Sh1 and decreased activity in Sh2 and LN. Evaluation of kinetic parameters revealed an increase of Vmax value by 37 % in Sh1 and decrease by 30 % in Sh2 and 17 % in LN. The KM value remained unchanged in Sh2 and LN, but was lower by 38 % in Sh1 indicating increased affinity of the ATP binding site, as compared to controls. During the activation with Na+ we observed increased Vmax by 64 % and increased KNa by 106 % in Sh1. In Sh2 we found decreased Vmax by 40 % and increased KNa by 38 %. In LN, the enzyme showed unchanged Vmax with increased KNa by 50 %. The above data indicate a positive role of increased activity of NOS in improved utilization of ATP as well as enhanced binding of Na+ by the cardiac Na, K-ATPase.

Effect of the pyridoindole antioxidant stobadine on ATP-utilisation by renal Na,K-ATPase in rats with streptozotocin-induced diabetes.

The effect of the pyridoindole antioxidant stobadine on diabetes-induced changes of Na,K-ATPase, especially those concerning the utilisation of its substrate ATP, was investigated. Sixteen weeks of streptozotocin-induced diabetes (single i.v. dose of streptozotocin; 55 mg/kg) was followed by decrease in the enzyme activity. This effect was emphasised in the presence of higher concentrations of substrate and in the presence of 8 mmol x l(-1) ATP it represented 20%. It might be a consequence of altered functional properties of Na,K-ATPase as suggested by 20% decrease in the V(max) value along with decrease in the K(m) value by 20%. Administration of 0.05% (w/w) stobadine in the diet to diabetic rats improved the function of renal Na,K-ATPase with respect to utilisation of ATP as suggested by significant increase in the enzyme activity in the whole concentration range of ATP investigated as a consequence of V(max) elevation to the level comparable to absolute controls. In conclusion, stobadine may play a positive role in restoring the functional properties of renal Na,K-ATPase, especially concerning the utilisation of energy derived from hydrolysis of ATP, improving thus the maintenance of ionic homeostasis during diabetes.