Effect of different vasodilators on NTPDase activity in healthy and hypertensive patients.

INTRODUCTION: The thrombogenic process that affects the hypertensive patient is associated with regulatory mechanisms present in the vascular endothelium. These mechanisms involve release of an endothelium-derived relaxing factor, ectonucleotidase activity and calcium ion concentration. METHODS: Interference with ENTPDase activity in platelets of hypertensive patients and healthy donors was evaluated for arginine, sodium nitroprusside, and hydralazine. In addition, the kinetic behavior of NTPDase was determined in the presence of the vasodilator that showed the greatest inhibitory influence. RESULTS: Vasodilators decreased NTPDase activity with ATP and ADP as substrates. In controls, hydrolysis was increased in the presence of arginine. Captopril did not affect enzyme activities. The dose response for increasing sodium nitroprusside was biphasic. Kinetic behavior studies were estimated in the presence of sodium nitroprusside, which caused a mixed inhibition. The K(m) values increased and V(max) decreased with increasing sodium nitroprusside concentrations. The IC(50) and K(i) values indicated that the vasodilator was a strong NTPDase inhibitor when tested for the control and hypertensive group, using ATP and ADP as substrate, respectively. CONCLUSION: It is postulated that there was an interaction between vasodilators, NO donors and inhibition of NTPDase.

Effect of high glucose levels in human platelet NTPDase and 5'-nucleotidase activities.

OBJECTIVES: The objective of this work was to evaluate the effect of different glucose levels on the ATP, ADP and AMP hydrolysis in the platelets of diabetic, hypertensive and diabetic/hypertensive participants. METHODS: The activities of the enzymes NTPDase (ATP and ADP hydrolysis) and 5'-nucleotidase (AMP hydrolysis), and CD39 expression were analyzed in human blood platelets of diabetic (DM-2), hypertensive (HT) and diabetic/hypertensive (DM-2/HT) patients. To evaluate the interference of glucose and fructose in NTPDase and 5'-nucleotidase activities, experiments were performed with glucose, fructose and mannitol concentrations ranging from 5 to 30 mM in platelet-rich plasma (PRP). Pre-incubation times of 10, 120 min and 24h were used. RESULTS: NTPDase and 5'-nucleotidase activities increased with increasing glucose and fructose concentrations (P<0.001) and the different times of pre-incubation did not interfere in ectonucleotidases activities (P>0.5). NTPDase and 5'-nucleotidase activities demonstrated a positive correlation between serum glucose levels and ATP and ADP hydrolysis in DM-2 and DM-2/HT patients. CD39 expression demonstrated that DM-2, HT and DM-2/HT groups presented a significant increase when compared to the control group (P<0.004). CONCLUSION: The hydrolysis of adenine nucleotides is enhanced in platelets of patients with diabetes and hypertension. We observed that an increasing glucose concentration had a direct effect on ATP, ADP and AMP hydrolysis. Furthermore, CD39 expression was enhanced in all patients groups, indicating that these enzyme activities are related with diabetes and hypertension.

Oxidative stress and erythrocyte acetylcholinesterase (AChE) in hypertensive and ischemic patients of both acute and chronic stages.

Ischemic stroke is a leading cause of mortality and disability particularly in the elderly. Hypertension is the most important risk factor in strokes, representing roughly 70% of all cases. Oxidative stress is believed to be one of the mechanisms taking part in neuronal damage in stroke. It is well documented that cholinergic system plays a key role in normal brain functions and in memory disturbances of several pathological processes, such as in cerebral blood flow regulation. This study investigated the oxidative status and acetylcholinesterase (AChE) activity in whole blood in patients diagnosed with acute and chronic stages of ischemia, as well as with hypertension. Malondialdehyde (MDA) levels and protein carbonylation content showed increased levels both in the acute ischemic groups and in the hypertensive group, when compared to the control. Catalase activity and reduced glutathione (GSH) levels in the acute group were also higher than in the hypertensive, chronic ischemic and control groups (p<0.05). The activity of AChE in acute ischemic patients was significantly higher than that presented by the control, hypertensive and chronic ischemic patients (p<0.05). The hypertensive group presented AChE activity significantly lower than control and chronic groups. In spite of having a defined location the ischemic event results in a systemic disorder that induces changes, which can be detected by measuring the peripheral markers of oxidative stress and AChE activity in erythrocytes.

Enhanced NTPDase and 5'-nucleotidase activities in diabetes mellitus and iron-overload model.

The activity of the enzymes NTPDase and 5'-nucleotidase was studied in both diabetes mellitus and an associated model of iron-overload. Rats were divided in five groups: citrate (CC), saline (S), diabetic (D), iron-overload (IO), and diabetic iron-overload (DIO). Diabetes was induced with alloxan (150 mg/kg), and iron-overload was induced with iron-dextran (10 intramuscular applications of +/-80 mg/kg). The enzymatic activities were evaluated in the platelets. The results demonstrated an increase in the activity of NTPDase with substrates ATP and ADP (60% and 120%, respectively; P<0.001), and 5'-nucleotidase (60%, P<0.001). This increase was more intense in the IO and DIO groups. The results obtained in vitro showed an activation in ATP, ADP, and AMP hydrolysis between 1 microM and 1,000 microM ferric nitrate concentrations, being more pronounced at 100 microM and decreasing at 1,000 microM. We concluded that diabetes mellitus in association with iron-overload increased the hydrolysis of adenine nucleotides in platelets, contributing to the abnormalities found in these pathological conditions.

Serum cholinesterase activity in diabetes and associated pathologies.

Serum cholinesterase activity was measured in diabetes, hypertensive and diabetic/hypertensive patients. The sample consisted of volunteer patients and was divided in a control group (n=26), type 2 diabetic group (n=16), hypertensive group (n=12) and type 2 diabetic/hypertensive group (n=26). In addition, blood glucose, cholesterol and triglyceride levels were determined. Serum cholinesterase activity in the control group was significantly lower in relation to the other groups (p<0.001). Blood glucose levels were elevated in type 2 diabetic and type 2 diabetic/hypertensive groups. In vitro studies showed increased cholinesterase activity in the presence of glucose 5-100mM or insulin 0.5-25 UI (p<0.001). Cholesterol and triglycerides were at normal levels only in the control group. Possibly, a relationship exists between the increase in serum cholinesterase and the vascular complications in the diabetic patients, potentially stimulated by the levels of glycemia and dyslipidemia. Although patients were receiving different medicines, the increase in enzyme activity was similar in all groups. This enzymatic profile suggests a possible interference of the diseases in the catalytic mechanism of the serum cholinesterase enzyme.

Efeito do extrato da casca de Syzygium cumini sobre a atividade da acetilcolinesterase em ratos normais e diabéticos / Syzygium cumini bark extract effect on acetylcholinesterase activity in normal and diabetic rats

Este estudo verificou a eficiência do extrato etanólico da casca de Syzygium cumini sobre o sistema colinérgico de ratos normais e diabéticos induzidos com aloxano. Os animais foram divididos em grupo controle (C), tratado com Syzygium cumini (TS), diabético (D) e diabético tratado com Syzygium cumini (DS). A atividade da acetilcolinesterase (AChE) foi analisada nas seguintes estruturas cerebrais: cerebelo, córtex, estriado e hipocampo. O extrato etanólico da casca de Syzygium cumini na dose de 1g.kg-1 foi administrado diariamente por um período de trinta dias. Foi verificado após este período que o extrato inibiu a atividade da AChE no cerebelo e córtex cerebral dos ratos do grupo DS (P<0,05), comparado com o TS. No estriado houve um aumento significativo na atividade da AChE nos ratos do grupo TS (P<0,01) comparado com o C, e no hipocampo não foi encontrada nenhuma variação significativa. Esses resultados indicam que o extrato da casca do Jambolão, possui um efeito inibitório da AChE no cerebelo e córtex cerebral e um efeito ativador sobre essa enzima no estriado, indicando uma possível alteração na funcionalidade do sistema colinérgico nestas estruturas cerebrais.

NTPDase and 5'-nucleotidase activities in rats with alloxan-induced diabetes.

Diabetes is associated with a hypercoagulable state. In this study, we investigated the potential effects of alloxan-induced diabetes on the activities of the enzymes NTPDase (E.C. 3.6.1.5, apyrase, ATP diphosphohydrolase, ecto/CD39) and 5'-nucleotidase (E.C. 3.1.3.5, CD73) that can control the levels of ADP and adenosine, two substances that regulates platelet aggregation. In the alloxan-treated rats, NTPDase activity was significantly increased by 88 and 35% with ATP as substrate and by 156 and 58% with ADP as substrate in platelets and synaptosomes, respectively (P< 0.05). AMP hydrolysis was increased by 142% (platelets) and 70% (synaptosomes) in diabetic rats compared to control. These results demonstrate that alloxan-induced diabetes interferes with ATP, ADP, and AMP hydrolysis in platelets and synaptosomes. Taken together, these results may indicate that in diabetic rats both NTPDase and 5'-nuleotidase from the central nervous system (CNS) and platelets respond similarly with increased activity. Thus, we speculate that platelets could be used as a potential peripheral marker of central alterations in NTPDase and 5'-nucleotidase activities in diabetes.

Enzymes that hydrolyze adenine nucleotides in diabetes and associated pathologies.

The activities of the enzymes NTPDase (E.C. 3.6.1.5, apyrase, ATP diphosphohydrolase, ecto-CD39) and 5'-nucleotidase (E.C. 3.1.3.5, CD73) were analyzed in platelets of type 2 diabetic, hypertensive and type 2 diabetic/hypertensive patients. The results showed an increase in platelet NTPDase activity in type 2 diabetic (34% and 72%), hypertensive (32% and 70%) and type 2 diabetic/hypertensive patients (30% and 55%) when compared to control (P<.01) with ATP and ADP as substrate, respectively. 5'-Nucleotidase activity was elevated in the hypertensive (60%) and type 2 diabetic/hypertensive (53%) groups when compared to the control and type 2 diabetic group (P<.01). No differences in sensitivity to inhibitors was detected between the platelets of controls and type 2 diabetic/hypertensive patients. No effects on the enzyme activities were observed when pharmacological doses of propranolol, captopril, furosemide, chlorpropamide, acetylsalicylic acid and glibenclamide were administered. Furthermore, changes in platelet adhesiveness and reactivity were found in all groups tested. In conclusion, we may postulate that NTPDase and 5'-nucleotidase from platelets are altered in patients with type 2 diabetes and hypertension. Probably, such alterations are involved in compensatory physiological responses in these diseases and are related to other important mechanisms of thromboregulation.