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Molecular approach to the calcium channel
Advances in Myocardiology
|January 1, 1985
Summary
Tritiated 1,4-dihydropyridines and other radioligands identify specific calcium channels in excitable tissues. These channels exhibit temperature-dependent binding, stereoselectivity, and cation requirements, with subtypes distinguished by drug interactions.
Area of Science:
- Pharmacology
- Molecular Biology
- Neuroscience
Background:
- Calcium channels are crucial for cellular excitability.
- Radioligands like 1,4-dihydropyridines are used to study these channels.
- Understanding channel properties is key to developing targeted therapies.
Purpose of the Study:
- To directly identify and characterize calcium channels in excitable tissues using radiolabeled ligands.
- To investigate the binding properties, regulation, and subtypes of these calcium channels.
Main Methods:
- Utilized tritiated 1,4-dihydropyridines (nimodipine, nitrendipine, nifedipine, PN 200-110), [3H]D-cis-diltiazem, and [3H]verapamil.
- Performed equilibrium binding studies on membranes from brain, heart, and skeletal muscle.
- Investigated temperature-dependence, reversibility, stereoselectivity, cation effects, and ligand-induced up/down-regulation.
Main Results:
- 1,4-Dihydropyridine calcium channel blockers bind with high affinity (0.2-2 nM) in a temperature-dependent, reversible, and stereoselective manner.
- Divalent cations are required for high-affinity binding, with observed cooperativity between cation and blocker binding sites.
- Calcium channels exhibit tissue-specific binding constants and can be classified into at least three subtypes based on drug interactions and regulation.
Conclusions:
- Identified distinct properties of 1,4-dihydropyridine binding sites on calcium channels.
- Demonstrated allosteric interactions and complex up/down-regulation mechanisms by various channel blockers.
- Established the existence of tissue-specific calcium channel subtypes with potential for subtype-selective drug development.