title: Species difference in modulation of calcium release by Naja naja kaouthia snake venom cardiotoxin in terminal cisternae from human and equine skeletal muscle.
abstract: The modulation of Ca2+ release by a cardiotoxin (CTX) from Naja naja kaouthia snake venom was examined in terminal cisternae-containing fractions from equine and human skeletal muscle. Pretreatment with CTX (10 microM) decreased by 27% (human muscle), or had no effect on (equine muscle), the threshold of Ca(2+)-induced Ca2+ release. If terminal cisternae fractions were first preloaded with Ca2+ to greater than 65% of the threshold of Ca(2+)-induced Ca2+ release and then CTX added, an immediate and sustained release of Ca2+ occurred in preparations from both species. Addition of CTX after a Ca2+ preload of less than 60% of the threshold of Ca(2+)-induced Ca2+ release did not elicit Ca2+ release in preparations from either species. Ruthenium red (10 microM) antagonized CTX-induced Ca2+ release, whereas dantrolene (10 microM) did not. These findings suggest that the effects of CTX on the Ca2+ release channel are dependent on Ca2+ preload and that CTX may be an important probe of the Ca(2+)-modulated Ca2+ release process and in understanding regulation of Ca2+ release in skeletal muscle from different species.
authors.affiliation: Department of Anesthesiology, Hahnemann University, Philadelphia, PA 19102-1192.
authors.forename: J E
authors.initials: JE
authors.lastname: Fletcher
authors.forename: L
authors.initials: L
authors.lastname: Tripolitis
authors.forename: J
authors.initials: J
authors.lastname: Beech
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004179:Cobra Cardiotoxin Proteins / Q000633:toxicity*; D003620:Dantrolene / Q000494:pharmacology; D006736:Horses; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D013045:Species Specificity; D013552:Swine
chemical_list: D004179:Cobra Cardiotoxin Proteins; D003620:Dantrolene; D002118:Calcium