Effect of polyphenolic compounds on the renal Na+,K(+)-ATPase during development and persistence of hypertension in rats

Effect of polyphenols extracts from Brassica vegetables on erythrocyte membranes (in vitro study)

The aim of this work was to estimate the in vitro effects of polyphenol extracts from Brassica vegetables (Brussels sprouts and red cabbage) on erythrocyte membranes with normal and high concentration of cholesterol. To determine the effect of phenolic compounds we prospectively studied cholesterol concentration, lipid peroxidation, membrane fluidity and ATPase activity. Polyphenol extracts from Brassica vegetables resulted in statistically significant reductions in cholesterol concentrations in hypercholesterolemic erythrocytes. For control erythrocytes, no significant reduction of cholesterol levels was observed for both extracts. Decreases in lipid peroxidation intensity were observed after incubation of hypercholesterolemic erythrocytes with the extracts. No changes in membrane fluidity for both extracts were noted for normal and hypercholesterolemic erythrocytes. The activity of ATPase decreased after incubation of normal and hypercholesterolemic erythrocytes with extract from Brassica vegetables. Our results indicate that polyphenols from red cabbage and Brussels sprout may directly influence erythrocyte membrane properties.

Acute treatment with polyphenol quercetin improves postischemic recovery of isolated perfused rat hearts after global ischemia

Quercetin is a plant-derived bioflavonoid with potentially beneficial effects on the cardiovascular system. Studies focused on the efficiency of flavonoids against ischemia-reperfusion (I/R) injury have demonstrated that quercetin exerts robust protective effects in renal, cerebral, and hepatic I/R models. However, there is only limited evidence about the effect of quercetin on myocardial I/R injury. Therefore, the aim of the current study was to examine the effect of quercetin on isolated rat heart during ischemia and reperfusion. Rat hearts perfused according to Langendorff at 37 degrees C were examined during 25 min global ischemia followed by 120 min reperfusion. Quercetin (15 micromol/L) was administered either 15 min before ischemia (group Q1), or during the entire reperfusion period (group Q2). Changes in functional parameters of the hearts were measured during the initial 40 min of reperfusion. At the end of the experiment, the hearts were stained with tetrazolium to estimate the size of infarction (IS). Our study showed that quercetin improved postischemic recovery of functional parameters of isolated hearts in both treated groups. This improvement was manifested by significantly higher values of left ventricular developed pressure (LVDP) and the maximal rates of pressure development and fall (+(dP/dt)max and -(dP/dt)max) and by significantly lower increase of end-diastolic pressure. Coronary flow was not significantly changed during reperfusion in the group treated before ischemia, but was significantly increased in the group treated during reperfusion. Quercetin also significantly reduced IS in both groups, more markedly in postischemically treated group. We conclude that acute quercetin treatment exerts significant positive effects on isolated hearts during I/R injury. These results are consistent with the beneficial effects of quercetin and other flavonoids on the cardiovascular system.

Dual effect of polyphenolic compounds on cardiac Na+/K+-ATPase during development and persistence of hypertension in rats

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 N(G)-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 V(max) 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 K(m) value (by 52% in LNPF4 vs. LN), suggesting worsened utilization of substrate by the enzyme. In sustained hypertension, however, Provinol had no effect on the ATP-binding site, as indicated by unchanged K(m) value (LNPF7/3 vs. LN). On the other hand, the Na(+)-binding site was protected by Provinol, as suggested by decreased K(Na) value (by 72% in LNPF4 and 69% in LNPF7/3 vs. LN), indicating an increased affinity of the enzyme for sodium. Thus, Provinol appeared to stimulate the extrusion of Na(+) from cardiac cells, especially in the physiologically important range of sodium concentrations (2-10 mmol*L(-1)), during both developing and sustained hypertension.

Effect of maturation on renal Na+/K+-atpase and its susceptibility to nitric oxide-deficient hypertension in rats

1. The present study deals with the effect of maturation on the kinetic properties of renal Na(+)/K(+)-ATPase and its susceptibility to nitric oxide (NO)-deficient hypertension induced by the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). 2. Immature (4-week-old) and adult (12-week-old) male Wistar rats were administered L-NAME (40 mg/kg per day) in their drinking water for 4 weeks. 3. The properties of the ATP- and Na(+)-binding sites of Na(+)/K(+)-ATPase were investigated by activation of the enzyme with increasing concentrations of the energy substrate ATP and/or cofactor Na(+). Unchanged values of K(m) suggest that energy utilization by the enzyme in the kidney of control rats remains unaffected during maturation. Conversely, the decrease in K(Na) values (the concentration of Na(+) necessary to achieve half-maximal reaction velocity) indicates improved affinity for Na(+) in the older group of control rats. 4. Application of L-NAME to all young animals had no significant effect on the functional properties of Na(+)/K(+)-ATPase. 5. In adult animals, the V(max) values remained unchanged after treatment with L-NAME, but the affinities of the ATP- and Na(+)-binding sites were decreased, as indicated by significant increase in K(m) and K(Na) values. 6. Maturation of control rats was accompanied by an increase in the Na(+) affinity of renal Na(+)/K(+)-ATPase without affecting ATP utilization. However, maturation increased the susceptibility of renal Na(+)/K(+)-ATPase to the harmful effects of L-NAME.

Oxidative stress and protective effects of polyphenols: comparative studies in human and rodent kidney. A review

Reactive oxygen species (ROS) play a key role in the pathophysiological processes of a wide range of renal diseases. Thus, antioxidants are expected to decrease the vulnerability of the kidney to oxidative challenges. Polyphenols, particularly abundant in red wine, could act as ROS scavengers, iron chelators and enzyme modulators. In addition, chronic exposure to moderate amounts of ethanol results in increased activity of the renal antioxidant enzymes, further supporting a renoprotective effect of red wine based on its antioxidant properties. An enhancement of plasma antioxidant capacity following red wine consumption has been reported both in man and rodents, thereby providing a contributory factor to its renoprotective effect because the kidney is a highly perfused organ. Although phenol concentration of red wine does not influence the activity of antioxidant enzymes of the kidney, the concentration of these compounds is negatively correlated with tissue lipid peroxidation, assessed by thiobarbituric acid reactive substances, and positively correlated with the antioxidant capacity of plasma. Moreover, amelioration of myoglobinuric renal damage was found in rats following chronic exposure to flavonol-rich red wine. Also, pretreatment with resveratrol, or other red wine polyphenols, decreased kidney damage caused by ischaemia-reperfusion. The aim of the present review is to examine the pathophysiological basis of the renoprotective effect of red wine in man and rodents, based on functional, biochemical and ultrastructural evidence.

Ultrastructure and histochemistry of rat myocardial capillary endothelial cells in response to diabetes and hypertension

Insufficient growth and rarefaction of capillaries, followed by endothelial dysfunction may represent one of the most critical mechanisms involved in heart damage. In this study we examined histochemical and ultrastructural changes in myocardial capillary endothelium in two models of heart failure streptozotocin-induced diabetes mellitus (STZ) and NO-deficient hypertension in male Wistar rats. Diabetes was induced by a single i.v. dose of STZ (45 mg/kg) and chronic 9-week stage was analysed. To induce NO-deficient hypertension, animals were treated with inhibitor of NO synthase L-nitroarginine methylester (L-NAME) (40 mg/kg) for 4 weeks. Left ventricular tissue was processed for enzyme catalytic histochemistry of capillary alkaline phosphatase (AlPh), dipeptidyl peptidase IV (DPP IV), and endothelial NO synthase/NADPH-diaphorase (NOS) and for ultrastructural analysis. In diabetic and hypertensive rats, lower/absent AlPh and DPP IV activities were found in focal micro-areas. NOS activity was significantly reduced and persisted only locally. Quantitative evaluation demonstrated reduction of reaction product intensity of AlPh, DPP and NOS by 49.50%, 74.36%, 20.05% in diabetic and 62.93%, 82.71%, 37.65% in hypertensive rats. Subcellular alterations of endothelial cells were found in heart of both groups suggesting injury of capillary function as well as compensatory processes. Endothelial injury was more significant in diabetic animals, in contrast the adaptation was more evident in hypertensive ones. CONCLUDING: both STZ-induced diabetes- and NO-deficient hypertension-related cardiomyopathy were accompanied by similar features of structural remodelling of cardiac capillary network manifested as angiogenesis and angiopathy. The latter was however, predominant and may accelerate disappearance of capillary endothelium contributing to myocardial dysfunction.