Effects of ruthenium red on membrane ionic currents in urinary bladder smooth muscle cells of the guinea-pig

Pflugers Arch. 1998 Apr;435(5):645-53. doi: 10.1007/s004240050565.


Three major ionic currents, Ca2+-dependent K+ current (IK-Ca), delayed rectifier type K+ current (Ikd) and Ca2+ current (ICa), were activated by depolarization under whole-cell clamp in single smooth muscle cells isolated from guinea-pig urinary bladder. Externally applied ruthenium red (RuR) reduced the amplitude of IK-Ca and ICa at 0 mV (IC50 values were 4.2 and 5.6 muM, respectively), but did not affect IKd. Spontaneous transient outward currents (STOCs) and caffeine-induced outward currents (Icaf) at -30 mV were reduced by external 10 muM RuR. When 10 muM RuR was added to the pipette solution, IK-Ca during depolarization, STOCs and Icaf significantly decreased with time. RuR did not change the unitary current amplitude of the large-conductance Ca2+-dependent K+ (BK) channels, but reduced the open probability of the channel under excised patch-clamp recording mode. RuR reduced the channel activity more effectively from the cytosolic face than from the other. This inhibition decreased when the cytosolic Ca2+ concentration was increased. These results indicate that RuR blocks BK and Ca2+ channels in urinary bladder smooth muscle cells. The decrease in IK-Ca, STOCs and Icaf by RuR is attributable to the direct inhibition of BK channel activity, probably in addition to the inhibition of Ca2+ release from storage sites. The direct inhibition of BK channel activity by RuR may be related to the interaction of RuR with the Ca2+-binding sites of the channel protein.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Caffeine / pharmacology
  • Calcium Channels / physiology
  • Delayed Rectifier Potassium Channels
  • Guinea Pigs
  • Ion Channels / drug effects*
  • Ion Channels / physiology
  • Large-Conductance Calcium-Activated Potassium Channels
  • Membrane Potentials / drug effects
  • Muscle, Smooth / cytology
  • Muscle, Smooth / drug effects*
  • Muscle, Smooth / physiology
  • Patch-Clamp Techniques
  • Potassium Channel Blockers
  • Potassium Channels / drug effects
  • Potassium Channels / physiology
  • Potassium Channels, Calcium-Activated*
  • Potassium Channels, Voltage-Gated*
  • Ruthenium Red / pharmacology*
  • Urinary Bladder / cytology
  • Urinary Bladder / drug effects*
  • Urinary Bladder / physiology


  • Calcium Channels
  • Delayed Rectifier Potassium Channels
  • Ion Channels
  • Large-Conductance Calcium-Activated Potassium Channels
  • Potassium Channel Blockers
  • Potassium Channels
  • Potassium Channels, Calcium-Activated
  • Potassium Channels, Voltage-Gated
  • Ruthenium Red
  • Caffeine