title: Bee venom melittin is a potent toxin for reducing the threshold for calcium-induced calcium release in human and equine skeletal muscle.
abstract: The modulation of Ca2+ release by synthetic bee venom melittin was examined in equine and human terminal cisternae-containing fractions. Melittin (0.1 microM) decreased the threshold of Ca(2+)-induced Ca2+ release by 20% in equine muscle and by 36% in human muscle. If terminal cisternae fractions were first preloaded with Ca2+ to greater than about 75% of the threshold of Ca(2+)-induced Ca2+ release and then melittin added, an immediate and sustained release of Ca2+ occurred in preparations from both species. Addition of melittin after a Ca2+ preload of < 50% of the threshold of Ca(2+)-induced Ca2+ release did not elicit sustained Ca2+ release. Ruthenium red (10 microM) antagonized all effects of melittin on Ca2+ release. Melittin (0.1-10 microM) did not affect [3H]ryanodine binding. Melittin (0.1 microM) slightly (10%) inhibited the Ca2+ pump and this action was not antagonized by ruthenium red. These findings suggest that melittin may be an important new probe of the Ca(2+)-modulated Ca2+ release process that does not act at the ryanodine binding site.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D046508:Culture Techniques; D006736:Horses / Q000378:metabolism*; D006801:Humans; D008555:Melitten / Q000138:chemical synthesis / Q000494:pharmacology*; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D012430:Ruthenium Red / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism
chemical_list: D012430:Ruthenium Red; D012433:Ryanodine; D008555:Melitten; D002118:Calcium