Abstract
Hemostatic abnormalities are commonly found in patients with renal failure.
Both a bleeding diathesis and the uremic prothrombotic state may be caused by
renal disease. The main role of blood platelets is to ensure primary hemostasis,
which is the maintenance of vessel integrity and cessation of bleeding upon injury.
While playing a major part in acute arterial thrombosis, platelets are also involved
in inflammation, atherosclerosis, and angiogenesis. When platelets are undergo
activation first adhere to the subendothelial matrix where they become activated
and release secondary agonists such as ATP, ADP, thromboxane A2, serotonin
and several other biologically active substances. ADP and ATP play a crucial role
in platelet activation, acting through P2 receptors. This release may be responsible
for the activation, recruitment, and induction of aggregation of additional platelets in
the microenvironment. Thus, the metabolism of ADP in the blood is important for
the regulation of platelet functions. NTPDase (ecto-CD39) is that hydrolyzes
extracellular adenosine tri- and diphosphate (ATP, ADP) to adenosine
monophosphate (AMP), which is subsequently converted into adenosine by 5’-
nucleotidase (CD73).
The objectives of this study were to explore the relations between platelet
dysfunction in uremia with hemostatic abnormalities and the severity of kidney
disease in patients with CRF under conservative treatment (nondialysed - ND) and
hemodialysis (HD) treatment companing to heathy subjects with the same age.
The activities of the enzymes NTPDase and 5´-nucleotidase were analyzed in
platelets from patients with chronic renal failure (CRF), both undergoing
hemodialysis treatment (HD) and not undergoing hemodialysis (ND), as well as
from a control group. The results showed an increase in platelet NTPDase activity
in CRF patients on HD treatment (52.88%) with ATP as substrate. ADP hydrolysis
was decreased (33.68% and 39.75%) in HD and ND patients, respectively. In
addition, 5’-nucleotidase activity was elevated in the HD (160%) and ND (81.49%)
groups when compared to the control group. Significant correlation was found
among ATP, ADP and AMP hydrolysis and plasma creatinine and urea levels.
Patients were compared statistically according the time of hemodialysis treatment.
We found enhanced NTPDase with ATP substrate and decrease with ADP
substrate, and increase in 5’-nucleotidase activity between 49 and 72 months on
HD patients. Our results suggest the existence of alterations in nucleotide
hydrolysis in platelets, which might contribute to abnormal homeostasis in renal
failure patients, thus and the enhanced risk of thromboembolic complication and
accelerated atherosclerosis in patients with renal failure.
Our knowledge about stimuli and sources of oxidative stress, and about its
role as an important cofactor contributing to endothelial dysfunction, inflammation,
atherosclerosis and glomerulosclerosis has substantially increase over the last
years. Cardiovascular disease (CVD) is the major cause of death in patients with
renal insufficiency, accounting for 50% of all deaths in renal replacement therapy
patients and in recipients of renal transplants. Mortality from CVD in patients with
renal insufficiency is approximately 9% per year, which is about 30 times the risk in
the general population.
Oxidative stress defines an imbalance between formation of reactive oxygen
species (ROS) and antioxidative defense mechanisms. In view of the profound
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