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A novel high affinity class of Ca2+ channel blockers
1Centre de Biochimie du Centre National de la Recherche Scientifique, Parc Valrose, Nice, France.
Molecular Pharmacology
|April 1, 1988
Summary
Benzolactams, a novel class of molecules, effectively block L-type calcium channels by binding with high affinity. These compounds inhibit various calcium channel antagonist classes, demonstrating broad efficacy in cellular and electrophysiological studies.
Area of Science:
- Pharmacology
- Molecular Biology
- Cardiovascular Research
Background:
- L-type calcium channels are crucial for cellular excitation and are targets for various cardiovascular drugs.
- 1,4-dihydropyridine derivatives are well-established blockers of L-type calcium channels.
- New classes of calcium channel blockers are sought for improved therapeutic profiles.
Purpose of the Study:
- To characterize the binding and functional properties of benzolactams (HOE 166 and analogs) as novel L-type calcium channel blockers.
- To investigate the interaction of benzolactams with known calcium channel antagonist binding sites.
- To evaluate the efficacy of benzolactams in inhibiting calcium influx in cellular models.
Main Methods:
- Radioligand binding assays using [3H]PN 200-110, [3H]HOE 166, and other labeled channel antagonists.
- Competition binding experiments to assess the interaction of HOE 166 with different classes of calcium channel blockers.
- 45Ca2+ uptake assays in rat aortic (A7r5) and insulin-secreting (RINm5F) cell lines.
- Voltage-clamp electrophysiology to confirm channel blockade.
Main Results:
- Benzolactams bind to a specific site on L-type calcium channels with high affinity (e.g., 0.25 nM for HOE 166).
- HOE 166 competitively inhibits 1,4-dihydropyridine binding and non-competitively inhibits binding of phenylalkylamines, benzothiazepines, and diphenylbutylpiperidines.
- Benzolactams effectively inhibit depolarization-induced 45Ca2+ influx in A7r5 and RINm5F cells.
- Structure-activity relationship studies show good correlation between binding affinity and functional blockade.
- Voltage-clamp experiments confirm complete blockade of voltage-dependent L-type calcium channels by HOE 166.
Conclusions:
- Benzolactams represent a new class of high-affinity L-type calcium channel blockers.
- They interact with the calcium channel at a site distinct from, yet allosterically linked to, the 1,4-dihydropyridine binding site.
- HOE 166 and its analogs demonstrate potent and effective blockade of L-type calcium channels, suggesting therapeutic potential.