Ca2+ channels, ryanodine receptors and Ca(2+)-activated K+ channels: a functional unit for regulating arterial tone

Acta Physiol Scand. 1998 Dec;164(4):577-87. doi: 10.1046/j.1365-201X.1998.00462.x.


Local calcium transients ('Ca2+ sparks') are thought to be elementary Ca2+ signals in heart, skeletal and smooth muscle cells. Ca2+ sparks result from the opening of a single, or the coordinated opening of many, tightly clustered ryanodine receptor (RyR) channels in the sarcoplasmic reticulum (SR). In arterial smooth muscle, Ca2+ sparks appear to be involved in opposing the tonic contraction of the blood vessel. Intravascular pressure causes a graded membrane potential depolarization to approximately -40 mV, an elevation of arterial wall [Ca2+]i and contraction ('myogenic tone') of arteries. Ca2+ sparks activate calcium-sensitive K+ (KCa) channels in the sarcolemmal membrane to cause membrane hyperpolarization, which opposes the pressure induced depolarization. Thus, inhibition of Ca2+ sparks by ryanodine, or of KCa channels by iberiotoxin, leads to membrane depolarization, activation of L-type voltage-gated Ca2+ channels, and vasoconstriction. Conversely, activation of Ca2+ sparks can lead to vasodilation through activation of KCa channels. Our recent work is aimed at studying the properties and roles of Ca2+ sparks in the regulation of arterial smooth muscle function. The modulation of Ca2+ spark frequency and amplitude by membrane potential, cyclic nucleotides and protein kinase C will be explored. The role of local Ca2+ entry through voltage-dependent Ca2+ channels in the regulation of Ca2+ spark properties will also be examined. Finally, using functional evidence from cardiac myocytes, and histological evidence from smooth muscle, we shall explore whether Ca2+ channels, RyR channels, and KCa channels function as a coupled unit, through Ca2+ and voltage, to regulate arterial smooth muscle membrane potential and vascular tone.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Arteries / cytology
  • Arteries / physiology
  • Calcium / physiology*
  • Calcium Channels / physiology*
  • Calcium Signaling / physiology*
  • Humans
  • Muscle Tonus / physiology
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / physiology*
  • Potassium Channels / physiology*
  • Ryanodine Receptor Calcium Release Channel / physiology*
  • Up-Regulation / physiology*


  • Calcium Channels
  • Potassium Channels
  • Ryanodine Receptor Calcium Release Channel
  • Calcium