title: Induction of calcium release from sarcoplasmic reticulum of skeletal muscle by xanthone and norathyriol.
abstract: 1. Effects of xanthone and its derivative, 1,3,6,7-tetrahydroxyxanthone (norathyriol), on Ca2+ release and ryanodine binding were studied in isolated sarcoplasmic reticulum (SR) vesicles from rabbit skeletal muscle. 2. Both xanthone and norathyriol dose-dependently induced Ca2+ release from the actively loaded SR vesicles which was blocked by ruthenium red, a specific Ca2+ release inhibitor, and Mg2+. 3. Xanthone and norathyriol also dose-dependently increased apparent [3H]-ryanodine binding. Norathyriol, but not xanthone, produced a synergistic effect on binding activation when added concurrently with caffeine. 4. In the presence of Mg2+, which inhibits ryanodine binding, both caffeine and norathyriol, but not xanthone, could restore the binding to the level observed in the absence of Mg2+. 5. Xanthone activated the Ca(2+)-ATPase activity of isolated SR vesicles dose-dependently reaching 70% activation at 300 microM. 6. When tested in mouse diaphragm, norathyriol potentiated the muscle contraction followed by twitch depression and contracture in either a Ca(2+) -free bathing solution or one containing 2.5 mM Ca2+. These norathyriol-induced effects on muscle were inhibited by pretreatment with ruthenium red or ryanodine. 7. These data suggest that xanthone and norathyriol can induce Ca2+ release from the SR of skeletal muscle through a direct interaction with the Ca2+ release channel, also known as the ryanodine receptor.
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, R.O.C.
authors.forename: J J
authors.initials: JJ
authors.lastname: Kang
authors.forename: Y W
authors.initials: YW
authors.lastname: Cheng
authors.forename: F N
authors.initials: FN
authors.lastname: Ko
authors.forename: M L
authors.initials: ML
authors.lastname: Kuo
authors.forename: C N
authors.initials: CN
authors.lastname: Lin
authors.forename: C M
authors.initials: CM
authors.lastname: Teng
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D003964:Diaphragm / Q000187:drug effects; D005260:Female; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009119:Muscle Contraction / Q000187:drug effects; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D012430:Ruthenium Red / Q000494:pharmacology; D012433:Ryanodine / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*; D014966:Xanthenes / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D044004:Xanthones
chemical_list: D015220:Calcium Channels; D009124:Muscle Proteins; D010726:Phosphodiesterase Inhibitors; D014966:Xanthenes; D044004:Xanthones; D012430:Ruthenium Red; D012433:Ryanodine; C069053:norathyriol; D002110:Caffeine; D011189:Potassium Chloride; C009689:xanthone; D000252:Calcium-Transporting ATPases; D008274:Magnesium; D002118:Calcium