L-type calcium channel
Also known as: voltage-gated calcium channel, Cav1.2, dihydropyridine receptor
A voltage-gated channel in the membrane of smooth-muscle and heart-muscle cells that lets calcium in when the cell is electrically excited. Calcium entry is what makes the muscle contract, so blocking the channel relaxes artery walls and, for some drugs, slows the heart.
- Kind
- ion channel
- Also called
- voltage-gated calcium channel, Cav1.2, dihydropyridine receptor
- Where it is found
- Cell membranes of vascular smooth muscle in arterioles and arteries, cardiac muscle and the heart's conduction tissue; also endocrine and nerve cells.
What it does
L-type ('long-lasting') calcium channels open when the membrane depolarises and stay open long enough for a substantial calcium current. In vascular smooth muscle the calcium that enters activates the contractile proteins directly, setting the tone of arterioles and therefore blood pressure. In heart muscle the same channel triggers a much larger release of calcium from internal stores with each beat, and in the sinoatrial and atrioventricular nodes it carries the current that generates and conducts the heartbeat. The dihydropyridine calcium channel blockers (amlodipine, felodipine, nifedipine) bind a site on the channel that is favoured in relaxed, depolarised vascular muscle, so they dilate arteries with little effect on the heart; verapamil and diltiazem bind differently and also slow the heart's nodes.
Role in the body
Sets arteriolar tone (blood pressure), drives cardiac contraction and conduction through the AV node, and contributes to insulin release and neurotransmitter release elsewhere in the body.