The aim of this study was to evaluate the substrate (ATP) kinetics of erythrocyte membrane Na, K-ATPase in children with borderline or essential hypertension. Although the activity of Na, K-ATPase in the presence of in vivo concentrations of ATP was not significantly altered, kinetic studies showed an obvious inhibition of enzyme activity in the erythrocyte membrane of children with borderline or essential hypertension. Hanes plot analysis revealed a decrease of V(max) from 7.19 in erythrocytes from control subjects to 4.93 and 3.33 in those from children with borderline or essential hypertension, respectively. A mean value of the K(m) decreased from 0.10 in the control to 0.08 and 0.02 in children with borderline or essential hypertension, respectively. The energy status of erythrocytes, estimated by ATP, ADP and AMP levels, ATP/ADP ratio, and adenylate energy charge (AEC) was not significantly changed in the cells from hypertensive children. The use of a free radical-generating system (FeSO4/ascorbate) in vitro significantly reduced enzyme activity in the control erythrocytes while in those from hypertensive children it was abolished completely. The level of lipid peroxides was considerably higher (+ 37 per cent) in the plasma, while that of reduced glutathione was significantly lower both in the erythrocytes and the plasma of children with essential hypertension than in healthy children. These results indicate significant alterations of the antioxidant status which could be the cause of the inhibited Na, K-ATPase activity in erythrocyte membranes from hypertensive children.
The principle objective of this investigation was to establish the frequency and form of the arterial hypertension in children between 7 and 16 years in urban and rural population. Specific goals were to determine by screening method, i.e., by elimination, the arterial hypertension prevalence in relation to permanent residence (town-village), age and sex of children; to determine, by the same method, the prevalence of the essential and borderline arterial hypertension; to test the risk factors in patients with essential and borderline arterial hypertension: obesity, hereditary predisposition (relatives of the first and second line), lipids, and ten-year follow-up of children with essential arterial hypertension. The examination included 3000 children (age 7-16 years) during regular school days. Essential arterial hypertension in this study was defined as blood pressure continuously higher than 95th percentile for age and sex in at least three different measurements; secondary causes of hypertension were excluded by available clinical, laboratory and functional investigations. Borderline hypertension was defined as blood pressure continually higher than 90th percentile, and from time to time higher than 95th percentile for age and sex in at least three measurements, when the secondary causes of hypertension were excluded. The obtained results were the basis for the following conclusions: Prevalence of arterial hypertension for all children was 0.93% and was the lowest in children aged 7-8 years (0.83%), and the highest in chil dren aged 15-16 years (2.96%). Prevalence of the essential arterial hypertension was 0.37% and of borderline arterial hypertension 0.56%. Prevalence of the arterial hypertension was higher in urban than in rural population of children (1.09:0.55%), but without statistically significant difference (p>0.05). Hypertension was verified in 60.7% of family members of children with increased blood pressure. 21.4% of hypertensive children were overweight. Hyperlipidemia was noted in 4 children with essential hypertension. All children with arterial hypertension underwent 24-hours Holter monitoring. Patients with essential arterial hypertension had sinus tachycardia in 95% and patients with borderline hypertension in 60% (in stress and pressure).
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