Discontinuous alterations of platelet structure and function by bound, ionizable verapamil

Area of Science:

• Pharmacology
• Biochemistry
• Cell Biology

Background:

• Verapamil is a known calcium channel blocker.
• Platelets play a crucial role in hemostasis and thrombosis.
• Understanding drug interactions with platelet membranes is vital for cardiovascular research.

Purpose of the Study:

• To investigate the effects of verapamil on platelet structure and function.
• To elucidate the mechanism of verapamil's action on platelets.
• To determine the active form of verapamil in platelet interactions.

Main Methods:

• Studied verapamil binding to platelets using adsorption isotherms.
• Analyzed verapamil's effect on platelet swelling and aggregation.
• Investigated the role of N-methylverapamil to identify the active verapamil species.

Main Results:

• Verapamil binding to platelets is saturable below a threshold concentration, exhibiting Langmuir adsorption.
• Above this threshold, binding becomes discontinuous, suggesting membrane disorganization.
• Verapamil causes platelet swelling and inhibits ADP-induced fibrinogen binding and aggregation; N-methylverapamil does not.

Conclusions:

• Verapamil alters platelet structure and function by disorganizing the platelet plasma membrane.
• Deprotonated verapamil is the active species responsible for these effects.
• These findings highlight verapamil's potential as a modulator of platelet activity through membrane interactions.