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.
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).
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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.
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