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Erythrocyte Na+,K(+)-ATPase activity does not predict therapeutic response to calcium antagonists in essential
T Tanyalçin1, F Kutay, I Soydan
1Department of Biochemistry, Ege University School of Medicine, Bornova, Izmir-Turkey.
Insights
Reduced erythrocyte membrane sodium-potassium adenosine triphosphatase (Na+,K(+)-ATPase) activity in hypertensive patients was restored after nitrendipine treatment. This enzyme activity may serve as a marker for predicting treatment response in hypertension management.
Area of Science:
- Biochemistry
- Cardiovascular Medicine
- Clinical Pharmacology
Background:
- Essential hypertension is characterized by altered erythrocyte membrane ion transport.
- Sodium-potassium adenosine triphosphatase (Na+,K(+)-ATPase) plays a crucial role in maintaining cellular ion balance.
- Investigating Na+,K(+)-ATPase activity could offer insights into hypertension pathophysiology and treatment response.
Purpose of the Study:
- To evaluate erythrocyte membrane Na+,K(+)-ATPase activity as a potential biomarker for screening hypertensive patients.
- To determine if pre- and posttreatment analysis of Na+,K(+)-ATPase activity can predict responsiveness to calcium channel blockers.
- To assess the impact of nitrendipine treatment on Na+,K(+)-ATPase activity and erythrocyte sodium/potassium content.
Main Methods:
- Erythrocyte Na+,K(+)-ATPase activity, sodium (ENa), and potassium (EK) content were measured in controls and untreated hypertensive patients.
- Measurements were taken before and after a 4-week treatment period with nitrendipine.
- Statistical analyses included comparisons between groups and correlation analyses.
Main Results:
- Untreated hypertensive patients exhibited significantly lower Na+,K(+)-ATPase activity compared to controls.
- Nitrendipine treatment significantly increased Na+,K(+)-ATPase activity in hypertensive patients.
- Pretreatment erythrocyte sodium content was significantly higher in hypertensive patients, normalizing post-treatment.
Conclusions:
- Erythrocyte membrane Na+,K(+)-ATPase activity is diminished in essential hypertension and is restored with nitrendipine treatment.
- While Na+,K(+)-ATPase activity normalizes, its relative change did not correlate with blood pressure reduction, suggesting complex mechanisms.
- Further research is needed to fully establish Na+,K(+)-ATPase as a predictive biomarker for antihypertensive treatment efficacy.
Abstract:
We investigated whether pre- and posttreatment analysis of erythrocyte membrane Na+,K(+)-ATPase (EC 3.6.1.37) activity would be a useful marker for screening hypertensive patients to determine who might benefit from treatment with calcium antagonists. Erythrocyte Na+,K(+)-ATPase activity and sodium and potassium (ENa, EK) contents were determined in controls and in patients with untreated essential hypertension before and after 4 weeks of treatment with nitrendipine. Na+,K(+)-ATPase activity was significantly (P < 0.0001) less in untreated hypertensive patients (n = 15; 104.60 +/- 29.37 nmol of phosphate produced per milligram of protein per hour) than in controls (n = 15, 171.87 +/- 34.42). After 4 weeks of nitrendipine treatment Na+,K(+)-ATPase activity was greater than in the pretreatment group: 158.13 +/- 26.80 (P < 0.001). Pretreatment ENa contents (22.34 +/- 4.77 mmol/L) were significantly (P < 0.0001) higher than in the normotensive group (13.14 +/- 3.32 mmol/L), but there was no significant difference between the controls and the posttreatment group (14.84 +/- 3.49 mmol/L). The control and pretreatment groups showed negative correlations between enzyme activity and systolic/diastolic blood pressure (P < 0.0001). The control and the posttreatment groups showed an inverse correlation between enzyme activity and ENa contents: r = -0.608 (P < 0.05) and r = -0.724 (P < 0.001), respectively. Although Na+,K(+)-ATPase is restored in hypertensive patients receiving nitrendipine treatment, relative changes in enzyme activity in relation to relative reduction in blood pressure response to treatment were not correlated.