L-type calcium channel

The L-type calcium channel is a type of voltage-dependent calcium channel. "L" stands for long-lasting referring to the length of activation. Like the others of this class, the α1 subunit is the one that determines most of the channel's properties. This channel lets L-type calcium current go through it. This current can be seen in Phase 2 of action potential of atrial, ventricular and Purkinje fibers. This is a slow inward current that is opposed by K current going outside.

L-type calcium channel blocker drugs are used as cardiac antiarrhythmics or antihypertensives, depending on whether the drugs have higher affinity for the heart (the phenylalkylamines, like verapamil), or for the vessels (the dihydropyridines, like nifedipine).

L-type channels are selectively blocked by benzothiazepines (like diltiazem).

See also: Cardiac_action_potential

In skeletal muscle, there is a very high concentration of DHP receptors, representing L-type calcium channels, situated in the T-tubules. Muscle depolarization results in large gating currents, but anomalously low calcium flux, which is now explained by the very slow activation of the ionic currents. For this reason, little or no Ca²⁺ passes across the T-tubule membrane during a single action potential.

Genes

• CACNA1C, CACNA1D, CACNA1S, CACNA1F

See also

• CACNA1C

External links

• "Voltage-Gated Calcium Channels". IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology. 
• L-Type Calcium Channel at the US National Library of Medicine Medical Subject Headings (MeSH)