Activation and inhibition of the sarcoplasmic reticulum Ca2+ channel by the polycationic dyes Hoechst 33342 and Hoechst 33258

J Membr Biol. 1993 Aug;135(2):109-18. doi: 10.1007/BF00231436.

Abstract

The polycationic dyes, Hoechst 33342 (Bisbenzimide,2'-(4-ethoxyphenyl)-5-(4-methyl-1-piperazinyl)-2,5'-bi-1H- benzimidazole) and Hoechst 33258 (Bisbenzimide,2'-(4-hydroxyphenyl)-5-(4-methyl-1-piperazinyl)- 2,5'-bi-1H-benzimidazole) alter the activity of the sarcoplasmic reticulum Ca2+ channel. Although they act competitively, Hoechst 33342 decreases, while Hoechst 33258 increases, the rate of channel-mediated Ca2+ efflux from junctional sarcoplasmic reticulum vesicles. Unlike other cationic sarcoplasmic reticulum Ca2+ channel antagonists, Hoechst 33342 blocks the ryanodine-activated Ca2+ channel. Both Hoechst 33342 and Hoechst 33258 inhibit the channel incorporated into the planar lipid bilayer. Since the only structural difference between the two dyes is that the agonist Hoechst 33258 has a hydroxy group where the antagonist Hoechst 33342 has an ethoxy group, it is possible that the more hydrophobic, bulky ethoxy group blocks Ca2+ movement through the channel, whereas the hydroxy group only reduces the rate of Ca2+ movement.

Publication types

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

MeSH terms

  • Adenosine Triphosphate / physiology
  • Animals
  • Benzimidazoles / pharmacology*
  • Bisbenzimidazole / pharmacology*
  • Calcium Channel Blockers
  • Calcium Channels* / analysis
  • Calcium Channels* / physiology
  • Cell Fractionation
  • Intracellular Membranes / physiology
  • Intracellular Membranes / ultrastructure
  • Lipid Bilayers
  • Membrane Potentials / physiology
  • Muscles / cytology
  • Muscles / physiology
  • Muscles / ultrastructure
  • Rats
  • Ryanodine / pharmacology
  • Sarcoplasmic Reticulum / chemistry*
  • Sarcoplasmic Reticulum / physiology
  • Sarcoplasmic Reticulum / ultrastructure

Substances

  • Benzimidazoles
  • Calcium Channel Blockers
  • Calcium Channels
  • Lipid Bilayers
  • Ryanodine
  • Adenosine Triphosphate
  • Bisbenzimidazole
  • bisbenzimide ethoxide trihydrochloride