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Calcium channels in thrombin-activated human platelet membrane
A Zschauer1, C van Breemen, F R Bühler
1Department of Research, University Hospital, Basel, Switzerland.
Nature
|August 25, 1988
Summary
Researchers identified novel divalent cation channels in human platelets activated by thrombin. These channels facilitate calcium entry, crucial for platelet activation, but differ from classical calcium channels.
Area of Science:
- Biochemistry
- Cell Biology
- Physiology
Background:
- Platelet activation by agonists like thrombin involves calcium influx.
- The specific ion channels responsible for this calcium entry remain unidentified.
Purpose of the Study:
- To identify and characterize ion channels involved in calcium entry into human platelets stimulated by thrombin.
- To elucidate the properties of these channels and compare them to known calcium channels.
Main Methods:
- Incorporation of membrane vesicles from human platelets into planar lipid bilayers.
- Measurement of unitary currents through single ion channels.
- Analysis of ion selectivity, conductance, and blockade by channel inhibitors.
Main Results:
- Single divalent cation-selective channels were identified exclusively in thrombin-stimulated platelets.
- These channels exhibit high selectivity for divalent cations and a conductance of approximately 10 pS (in 150 mM Ba2+).
- The channels are sensitive to blockade by inorganic blockers like Ni2+ but are not voltage-dependent and are insensitive to 1,4-dihydropyridine antagonists.
Conclusions:
- Thrombin-activated human platelets possess unique divalent cation channels mediating calcium entry.
- These channels represent a novel pathway for calcium influx distinct from voltage-dependent calcium channels.
- Further research into these channels could reveal new therapeutic targets for platelet-related disorders.