Calcium antagonists. Some chemical-pharmacologic aspects

Area of Science:

• Pharmacology
• Cell Biology
• Biochemistry

Background:

• Calcium ions (Ca++) are critical regulators of numerous cellular processes.
• Diverse mechanisms control cellular Ca++ levels, leading to various Ca++-antagonistic drugs.
• Calcium channel blockers, including verapamil and nifedipine, target potential-dependent Ca++ channels.

Purpose of the Study:

• To review fundamental questions regarding the action of Ca++ channel antagonists.
• To explore the specificity and mechanisms of Ca++ channel blockade.
• To understand the selectivity of these agents across different tissues and cellular functions.

Main Methods:

• Review of existing literature on Ca++ channel antagonists.
• Analysis of structure-activity relationships to infer specific binding sites.
• Comparison of antagonist activity on different Ca++ channels and non-Ca++ mediated processes.

Main Results:

• Ca++ channel antagonists demonstrate specific sites of action, not nonspecific membrane stabilization.
• These agents competitively inhibit Ca++ uptake, with cellular Ca++ uptake and contractile responses being equisensitive.
• Significant selectivity exists between cardiac and smooth muscle, and potentially different vascular beds.
• Ca++ channels involved in stimulus-secretion coupling are less sensitive than those in excitation-contraction coupling.

Conclusions:

• Ca++ channel antagonists possess specific mechanisms and sites of action.
• Their selectivity for different Ca++ channels and tissues is a key characteristic.
• Potential off-target effects on non-Ca++ mediated processes occur at higher concentrations and their therapeutic relevance is unclear.