T-type calcium channels may provide a unique target for cardiovascular therapy

Calcium ions generate depolarizing electrical currents when they cross the plasma membrane, and bind to members of an extended family of Ca2+-bindine proteins within cells; they can then participate in a wide variety of signa lling functions. In cardiovascular regulation, Ca2+ activates contraction o f both cardiac and vascular smooth muscle. The ability of Ca2+ to enter cel ls depends on members of an extended family of highly regulated Ca2+ channe ls. In the cardiovascular system, the most important are L- and T-type Ca2 channels, which serve different roles. Both activate vascular smooth muscl e and both contribute to the depolarizing currents in the sinus node pacema ker that control heart rate. However, only the L-type Ca2+ channels are imp ortant in activating contraction of the working cells of the atria and vent ricles, while cardiac T-type Ca2+ channels appear to stimulate cell growth and proliferation.