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Cell membrane cation transport systems during aldosterone antagonism
1Department of Molecular and Cardiovascular Research, University of Leuven (KULeuven), Belgium.
Abstract:
We conducted a double-blind, placebo-controlled parallel study of the effect of the aldosterone antagonist spironolactone, administered once daily for 1 week to normal male subjects, on blood pressure, intracellular cationic concentrations, and transmembrane cation transport systems and plasma or urinary variables. After a 1-week run-in period on placebo, the subjects (n = 40) were allocated to a placebo or a spironolactone group. Placebo or 100 mg spironolactone was administered once daily in the morning for 1 week. All subjects were investigated at baseline and after 1 week of placebo or spironolactone administration. Standing systolic blood pressure of subjects in the spironolactone group was decreased (p < 0.001) as compared with that of subjects in the placebo group, but standing diastolic blood pressure did not change. Decreased intraerythrocyte and intraplatelet Na+ and free Ca2+ concentration and decreased activity of the platelet Na(+)-pump activity were observed in the spironolactone-treated subjects. The intraerythrocyte and intraplatelet K+ and Mg2+ concentrations, as well as the activities of the erythrocyte Na+, Li(+)-countertransporter and Na+, K(+)-cotransporter, and Na+ and K+ leakage, were not changed during spironolactone administration. The blood pressure-lowering action of spironolactone in men in the standing position is accompanied by a decrease in cytosolic free platelet Ca2+ concentration, by a reduction in intraplatelet and intraerythrocyte Na+ concentration, and in the platelet Na+ pump activity.
Insights
Spironolactone significantly lowered systolic blood pressure in men by reducing intracellular sodium and calcium concentrations and platelet sodium pump activity. This aldosterone antagonist impacts cation transport, affecting blood pressure regulation.
Area of Science:
- Cardiovascular Pharmacology
- Renal Physiology
- Cellular Physiology
Background:
- Aldosterone antagonists, like spironolactone, are used to manage hypertension.
- The precise mechanisms by which spironolactone affects intracellular cation concentrations and transport remain under investigation.
Purpose of the Study:
- To investigate the effects of spironolactone on blood pressure, intracellular cation concentrations, and cation transport systems in healthy male subjects.
- To elucidate the relationship between spironolactone's blood pressure-lowering effects and changes in cellular ion homeostasis.
Main Methods:
- A double-blind, placebo-controlled parallel study was conducted over 1 week.
- Subjects received either placebo or 100 mg spironolactone daily.
- Measurements included blood pressure, intracellular cationic concentrations (Na+, Ca2+, K+, Mg2+), and transmembrane cation transport system activity.
Main Results:
- Spironolactone significantly decreased standing systolic blood pressure compared to placebo (p < 0.001).
- No significant changes were observed in standing diastolic blood pressure.
- Spironolactone treatment led to decreased intraerythrocyte and intraplatelet Na+ and free Ca2+ concentrations.
- Platelet Na+-pump activity was reduced, while erythrocyte Na+, Li(+)-countertransporter, Na+, K(+)-cotransporter, and cation leakage remained unchanged.
Conclusions:
- Spironolactone's blood pressure-lowering effect in men is associated with reduced cytosolic free platelet Ca2+ concentration.
- The study demonstrates a reduction in intraplatelet and intraerythrocyte Na+ concentration and platelet Na+ pump activity.
- These findings suggest that spironolactone influences cellular cation balance, contributing to its antihypertensive action.