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Platelet calcium pump activity in essential hypertensives and their first-degree relatives
S Gulati1, M Khullar, B K Sharma
1Department of Experimental Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
Insights
Essential hypertension patients show decreased platelet Ca2+-ATPase activity, potentially leading to elevated intracellular calcium. This reduced activity may serve as a novel biomarker for essential hypertension.
Area of Science:
- Biochemistry
- Cardiovascular Medicine
- Cell Biology
Background:
- Elevated intracellular free calcium (Ca2+) levels are observed in platelets of essential hypertension patients.
- Platelet Ca2+-pump activity is crucial for regulating intracellular Ca2+ homeostasis.
Purpose of the Study:
- To characterize the Ca2+-pump activity of platelet membranes in essential hypertensive patients.
- To investigate the relationship between Ca2+-ATPase activity, membrane cholesterol, and essential hypertension.
Main Methods:
- A double-blind study comparing untreated and treated essential hypertensives with normotensive controls.
- Analysis of Ca2+ activation kinetics, Vmax, and Km of platelet Ca2+-ATPase.
- Measurement of platelet membrane cholesterol content.
Main Results:
- Essential hypertensive patients exhibited significantly decreased Vmax for plasma and intracellular membranes and decreased Km for intracellular membranes.
- Increased platelet membrane cholesterol content was noted in essential hypertensive patients.
- Lowered Ca2+ efflux by Ca2+-ATPase was observed, correlating with elevated intracellular Ca2+.
Conclusions:
- Reduced Ca2+-ATPase activity in platelets may contribute to elevated intracellular free Ca2+ in essential hypertension.
- Decreased Ca2+-ATPase activity could be a potential biomarker for essential hypertension.
Abstract:
Intracellular free Ca2+ concentration has been shown to be elevated in platelets of patients with essential hypertension. This study was designed to characterize Ca(2+)-pump activity of the platelet membranes (surface and intracellular) in these patients A double-blind study was carried out. Untreated and treated (on beta-blockers) essential hypertensives were studied in comparison with normotensive control subjects. First degree blood relatives of essential hypertensives were also studied. The Ca2+ activation kinetics of the enzyme showed a significant decrease in the Vmax (for the plasma- and intracellular membranes) and Km (for the intracellular membranes) in the essential hypertensive patients. Increased platelet membrane cholesterol content was observed in these patients. Lowered Ca2(+)-efflux by Ca2(+)-ATPase may lead to elevated intracellular free Ca2(+)-levels in platelet of essential hypertensives. A lowered Ca2(+) -ATPase activity may emerge as a marker for essential hypertension.