Ion Channels and Vascular Tone

Abstract

Ion channels in the plasma membrane of vascular muscle cells that form the walls of resistance arteries and arterioles play a central role in the regulation of vascular tone. Current evidence indicates that vascular smooth muscle cells express at least 4 different types of K + channels, 1 to 2 types of voltage-gated Ca 2+ channels, ≥2 types of Cl − channels, store-operated Ca + (SOC) channels, and stretch-activated cation (SAC) channels in their plasma membranes, all of which may be involved in the regulation of vascular tone. Calcium influx through voltage-gated Ca 2+, SOC, and SAC channels provides a major source of activator Ca 2+ used by resistance arteries and arterioles. In addition, K + and Cl − channels and the Ca 2+ channels mentioned previously all are involved in the determination of the membrane potential of these cells. Membrane potential is a key variable that not only regulates Ca +2 influx through voltage-gated Ca 2+ channels, but also influences release of Ca 2+ from internal stores and Ca 2+ -sensitivity of the contractile apparatus. By controlling Ca 2+ delivery and membrane potential, ion channels are involved in all aspects of the generation and regulation of vascular tone. Keywords muscle; smooth; vascular; arterioles; potassium channels; calcium channels; vascular resistance; vasoconstriction Vascular tone, the contractile activity of vascular smooth muscle cells in the walls of small arteries and arterioles, is the major determinant of the resistance to blood flow through the circulation. Thus, vascular tone plays an important role in the regulation of blood pressure and the distribution of blood flow between and within the tissues and organs of the body. Regulation of the contractile activity of vascular smooth muscle cells in the systemic circulation is dependent on a complex interplay of vasodilator and vasoconstrictor stimuli from circulating hormones, neurotransmitters, endothelium-derived factors, and blood pressure. All of these signals are integrated by vascular muscle cells to determine the activity of the contractile apparatus of the muscle cells and hence the diameter and hydraulic resistance of a blood vessel. Ion channels play a central role in this process. Like all muscle cells, vascular smooth muscle uses Ca 2+ as the trigger for contraction. Calcium influx through channels in the plasma membrane and Ca 2+ release from intracellular stores are the major source of activator Ca 2+ . In addition, the movement of ions through ion channels determines, to a large extent, membrane potential. Membrane potential, along with cytosolic Ca 2+ concentration, regulates and modulates the influx 1,2 and release 3-5 of Ca 2+ through ion channels and the sensitivity of the contractile machinery to Ca 2+.6 Vascular smooth muscle cells express ≥4 different types of K + channels, 7,8 1 to 2 types of voltage-gated Ca 2+ channels, 1,2 ≥2 types of Cl − channels, 9-11 store-operated Ca + channels, 12,13 and stretch-activated cation channels 14-16 in their plasma membranes, all of which may...

Chemical composition and cardiovascular effects induced by the essential oil of Cymbopogon citratus DC. Stapf, Poaceae, in rats

“…The electrochemical gradient for K + ions is such that opening of K + channels results in diffusion of this cation out of the cells and membrane hyperpolarization. This effect closes Ca 2+ channels and leads to vasodilatation (Jackson, 2000).…”

Magnesium lithospermate B dilates mesenteric arteries by activating BKCa currents and contracts arteries by inhibiting KV currents

“…The representative currents in response to MLB (100 μmol/L) are illustrated ( Figure 5A). Application of 3 mmol/L 4-AP suppressed the currents almost completely, which is characteristic of K V currents [15,16] . The I K was sampled between 450 and 490 ms (steady state) to exclude any possibility of A-current contribution to the measured amplitude.…”

“…Force and membrane potential are closely coupled in arterial smooth muscle, and K + conductance plays a major role in determining membrane potential [15] . Low concentrations (≤1 mmol/L) of TEA selectively block BK Ca [17] .…”

Bioelectric impact of pathological angiogenesis on vascular function

“…Because almost nothing is known about the electrogenic profile of neovascular complexes and how these complexes functionally interact with their parent vessels, we focused on the bioelectric features of neovascularization. These gaps in knowledge are surprising, considering that it is well established that the transmembrane voltage of vascular cells (1), as well as electrotonic cell-cell interactions within a vascular network (2)(3)(4), play vital roles in regulating blood flow.…”