Disulfonic stilbene derivatives open the Ca2+ release channel of sarcoplasmic reticulum.
Ca2+ channels of isolated sarcoplasmic reticulum were incorporated into a planar lipid bilayer and their pharmacological properties were studied. The results show that the channel is a Ca2+-induced Ca2+ release channel like that observed in skinned muscle fibers and isolated vesicles. (i) The open channel probability was increased by the addition of micromolar amounts of Ca2+ to the cis (myoplasmic) side and further increased by millimolar ATP. (ii) The channel was closed by millimolar Mg2+ and micromolar ruthenium red. We found that two disulfonic stilbene derivatives, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and 4-acetoamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), when added to the cis side open the channel and lock it irreversibly at open without changing the single channel conductance. Ca2+ efflux from SR vesicles was also enhanced by SITS and DIDS, as monitored by a tracer assay. Further, Ag+ activated the channel transiently. These results suggest that certain amino and SH residues play important roles in gating the Ca2+ channel.
Kawasaki
T
T
Department of Biophysical Engineering, Faculty of Engineering Science, Osaka University.
Kasai
M
M
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D015220:Calcium Channels / Q000502:physiology*; D002132:Calcium Radioisotopes; D008274:Magnesium / Q000494:pharmacology; D012430:Ruthenium Red / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure; D012834:Silver / Q000494:pharmacology; D013267:Stilbenes / Q000494:pharmacology*
D015220:Calcium Channels; D002132:Calcium Radioisotopes; D013267:Stilbenes; D012430:Ruthenium Red; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D012834:Silver; D000255:Adenosine Triphosphate; D008274:Magnesium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium