Cardiovascular Drug Targets
An overview of the molecular and cellular targets exploited by cardiovascular drugs, from ion channels and receptors to enzymes and transporters.
## Overview
Cardiovascular pharmacology centers on a defined set of molecular targets that regulate heart rate, contractility, vascular tone, blood volume, and coagulation. Understanding these targets explains why specific drug classes work and how side effects arise.
## G-Protein-Coupled Receptors
Adrenergic receptors dominate cardiac pharmacology. Beta-1 receptors on cardiomyocytes increase heart rate and contractility when stimulated by norepinephrine. Beta-2 receptors on vascular smooth muscle mediate vasodilation. Alpha-1 receptors on arteriolar smooth muscle cause vasoconstriction. Muscarinic M2 receptors on nodal tissue slow heart rate via vagal tone. Angiotensin II type 1 (AT1) receptors drive vasoconstriction, aldosterone release, and cardiac remodeling.
## Ion Channels
Voltage-gated sodium channels (Nav1.5) initiate the cardiac action potential. L-type calcium channels (Cav1.2) sustain the plateau phase and trigger contraction. Potassium channels (hERG/Kv11.1, KATP) control repolarization. Funny channels (HCN4) in the sinoatrial node set pacemaker rate. Each channel type is a target for distinct antiarrhythmic or rate-controlling agents.
## Enzymes
Angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II. HMG-CoA reductase is the rate-limiting enzyme in cholesterol biosynthesis. Cyclooxygenase-1 (COX-1) in platelets produces thromboxane A2, promoting aggregation. Phosphodiesterase-3 (PDE3) degrades cAMP in cardiomyocytes, so its inhibition increases contractility.
## Transporters and Other Targets
The Na+/K+-ATPase pump is inhibited by cardiac glycosides, raising intracellular calcium. The norepinephrine transporter (NET) is relevant to sympathomimetic agents. Coagulation factors (thrombin, Factor Xa) are targeted by anticoagulants. The P2Y12 receptor on platelets is the target of clopidogrel and ticagrelor.
## Clinical Relevance
Most cardiovascular patients take drugs hitting multiple targets simultaneously. A typical heart failure regimen may include an ACE inhibitor (enzyme), a beta-blocker (GPCR), a diuretic (transporter), and an anticoagulant (coagulation factor). Understanding each target helps predict interactions and adverse effects.
## Key Takeaways
- Cardiovascular drugs target GPCRs, ion channels, enzymes, transporters, and coagulation factors
- Beta-adrenergic, muscarinic, and angiotensin receptors are the most exploited GPCRs
- Ion channel targets differ by cardiac tissue type and action potential phase
- Polypharmacy in cardiology requires awareness of overlapping target effects