Diversity of Potassium Channels in Human Umbilical Artery Smooth Muscle Cells: A Review of Their Roles in Human Umbilical Artery Contraction

Abstract

Through their control of cell membrane potential, potassium (K þ ) channels are among the best known regulators of vascular tone. This article discusses the expression and function of K þ channels in human umbilical artery smooth muscle cells (HUASMCs). We review the bibliographic reports and also present single-channel data recorded in freshly isolated cells. Electrophysiological properties of big conductance, voltage-and Ca 2þ -sensitive K þ channel and voltage-dependent K þ channels are clearly established in this vessel, where they are involved in contractile state regulation. Their role in the maintenance of membrane potential is an important control mechanism in the determination of the vessel diameter. Additionally, small conductance Ca 2þ -sensitive K þ channels, 2-pore domains K þ channels and inward rectifier K þ channels also appear to be present in HUASMCs, while intermediate conductance Ca 2þ -sensitive K þ channels and ATP-sensitive K þ channels could not be identified. In both cases, additional investigation is necessary to reach conclusive evidence of their expression and/or functional role in HUASMCs. Finally, we discuss the role of K þ channels in pregnancy-related pathologies like gestational diabetes and preeclampsia.

The Effects of Potassium Channels in Human Internal Mammary Artery

“…Activation of vascular smooth muscle by agonists such as NA not only causes an increase in calcium release from intracellular stores, but also depolarizes the membrane potential as well. However, there are studies suggesting that 4-AP may cause intracellular alkalinization and/or calcium release from the sarcoplasmic reticulum in different vascular segments, and by muscarinic receptor activation it may indirectly activate the BK Ca -sensitive potassium flow and it causes membrane hyperpolarization and results in relaxation [4]. This indirect hyperpolarizing effect of 4-AP has correlation with our results.…”

How is the human umbilical artery regulated?

“…The arterial smooth muscle tonus are also regulate by the ion flux. The activation of the K + channels is considered the main responsible for relaxation . In addition to being the most abundant in SMC, K + channels also play a key role in the regulation of resting potential, since they can directly control K + and indirectly Ca 2+ concentrations .…”

“…Regarding the HUA, it was already demonstrated the presence of several K + channels, such as small‐conductance Ca 2+ ‐activated K + channels (SKCa), 2‐pore domains K + channels (K 2P ) and inwardly rectifying K + channels (K IR ). While, on the other hand, the presence of intermediate‐conductance Ca 2+ ‐activated K + channels (IK Ca ) or ATP‐sensitive K + channels (K ATP ) is controversy, some studies report the protein presence, but the activity has never been measured . The activation of the K + channels appears to be the main responsible for the vasorelaxation verified in SMC from HUA.…”

“…The activation of the K + channels appears to be the main responsible for the vasorelaxation verified in SMC from HUA. The voltage‐gated K + channels (K v ) can regulate the membrane potential in response to membrane depolarization; while large‐conductance Ca 2+ ‐activated K + channels (BK Ca ) respond to changes of the intracellular Ca 2+ levels . Thus, it is notorious that more studies are needed regarding the functional role and expression of the K + channels in HUA to clarify the mechanisms envolved in the relaxation.…”

Roles of ion channels in regulation of acetylcholine-mediated vasoconstrictions in umbilical cords of rabbit/rats

“…BK and Kv channels are two major functional units [36]. This study was the first in demonstration of whole-cell K + currents in rat umbilical venous SMCs.…”