Abstract
In this study, we investigated the effects of peritoneal dialysis on hemorheological and hematological parameters and their relations with oxidant and antioxidant status of uremic patients. Hemorheological parameters (erythrocyte deformability, erythrocyte aggregation, osmotic deformability, blood and plasma viscosity) were measured in patients with renal insufficiency undergoing peritoneal dialysis (PD) and volunteers. Erythrocyte deformability, osmotic deformability and aggregation in both autologous plasma and 3% dextran 70 were measured by laser diffraction ektacytometry. Enzyme activities of glutathione peroxidase, superoxide dismutase and catalase were studied in erythrocytes; lipid peroxidation was studied by measuring the amount of malondialdehyde in both erythrocytes and plasma samples. Blood viscosity at native hematocrit was significantly lower in PD patients at all measured shear rates compared to controls, but it was high in PD patients at corrected (45%) hematocrit. Erythrocyte deformability did not show any difference between the two groups. Osmotic deformability was significantly lower in PD patients compared to controls. Aggregation index values were significantly high in PD patients in plasma Catalase and glutathione peroxidase activities in erythrocytes were decreased in PD patients whereas superoxide dismutase activity was increased compared to controls. Malondialdehyde was significantly increased in erythrocytes and plasma samples of PD patients which also shows correlations with aggregation parameters. It has been concluded that erythrocytes in PD patients are more prone to aggregation and this tendency could be influenced by lipid peroxidation activity in patient’s plasma. These results imply that uremic conditions, loss of plasma proteins and an increased risk of oxidative stress because of decreasing levels of antioxidant enzymes affect erythrocyte rheology during peritoneal dialysis. This level of distortion may have crucial effects, impairing the blood flow dynamics and causing inadequate microcirculatory perfusion.
Highlights
Erythrocytes are continuously exposed to hyperosmolarity in the kidney medulla
EPO is an essential hormone for erythrocyte production and so, anemia commonly occurs in people with end stage renal disease (ESRD) [5]
A list of patients (n = 24) with ESRD who have been undergoing continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD) for at least one year was obtained from the Department of Internal Medicine, Division of Nephrology of Istanbul Faculty of Medicine (Istanbul University, Turkey)
Summary
Erythrocytes are continuously exposed to hyperosmolarity in the kidney medulla. While they are passing through these areas, the contact time of erythrocytes is too short to induce eryptosis [1, 2]. Erythrocytes normally defend themselves via their antioxidant systems against oxidative stress in vivo They are protected by the inhibition of cation channels by Cl- and blunting sphingomyelinase by high urea concentration prevailing in kidney medulla [2]. Osmotic cell shrinkage opens non-selective cation channels in the erythrocyte membrane [3]. These channels are activated by oxidative stress. Exposure to osmotic shock or oxidative stress triggers Ca2+ uptake of erythrocytes and Ca2+ stimulates cell membrane scrambling with breakdown of phosphatidylserine asymmetry of the erythrocyte membrane. This leads to the translocation of phosphatidylserine to the erythrocyte surface and subsequent erythrocyte death. Besides the lack of EPO, shortened erythrocyte lifespan has been accepted as one of the contributory factors to anemia in patient with ESRD [6, 7]
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