L-type calcium channel

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The L-type calcium channel (also known as the DHP receptor) is a type of voltage-dependent calcium channel. "L" stands for long-lasting referring to the length of activation. L-type calcium channels are responsible for excitation-contraction coupling of skeletal, smooth, and cardiac muscle and for hormone secretion in cells in endocrine glands.

This channel lets L-type calcium current go through it. This current can be seen in Phase 2 of the action potential of atrial, ventricular and Purkinje fibers. This is a slow inward current that is opposed by K current going outside.

As with other sub-types of voltage-gated calcium channel, 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).

In skeletal muscle, there is a very high concentration of 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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