title: Eugenol-induced contractions of saponin-skinned fibers are inhibited by heparin or by a ryanodine receptor blocker.
abstract: The effects of eugenol on the sarcoplasmic reticulum (SR) and contractile apparatus of chemically skinned skeletal muscle fibers of the frog Rana catesbeiana were investigated. In saponin-skinned fibers, eugenol (5 mmol/L) induced muscle contractions, probably by releasing Ca(2+) from the SR. The Ca(2+)-induced Ca(2+) release blocker ruthenium red (10 micromol/L) inhibited both caffeine- and eugenol-induced muscle contractions. Ryanodine (200 micromol/L), a specific ryanodine receptor/Ca(2+) release channel blocker, promoted complete inhibition of the contractions induced by caffeine, but only partially blocked the contractions induced by eugenol. Heparin (2.5 mg/mL), an inositol 1,4,5-trisphosphate (InsP3) receptor blocker, strongly inhibited the contractions induced by eugenol but had only a small effect on the caffeine-induced contractions. Eugenol neither altered the Ca(2+) sensitivity nor the maximal force in Triton X-100 skinned muscle fibers. These data suggest that muscle contraction induced by eugenol involves at least 2 mechanisms of Ca(2+) release from the SR: one related to the activation of the ryanodine receptors and another through a heparin-sensitive pathway.
authors.affiliation: Departamento de Fisiologia, Setor de Ciências Biológicas, Centro Politécnico, Universidade Federal do Paraná, Curitiba, Paraná, Brazil.
authors.forename: Marco S
authors.initials: MS
authors.lastname: Lofrano-Alves
authors.forename: Edson L
authors.initials: EL
authors.lastname: Oliveira
authors.forename: Carlos E N
authors.initials: CE
authors.lastname: Damiani
authors.forename: Ilana
authors.initials: I
authors.lastname: Kassouf-Silva
authors.forename: Rosalvo T H
authors.initials: RT
authors.lastname: Fogaça
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D005054:Eugenol / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D005260:Female; D006493:Heparin / Q000494:pharmacology*; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D018485:Muscle Fibers, Skeletal / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects*; D017830:Octoxynol; D011892:Rana catesbeiana; D012430:Ruthenium Red / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects*; D012503:Saponins / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D013501:Surface-Active Agents
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D012503:Saponins; D013501:Surface-Active Agents; D012430:Ruthenium Red; D002110:Caffeine; D005054:Eugenol; D015544:Inositol 1,4,5-Trisphosphate; D017830:Octoxynol; D006493:Heparin; D002118:Calcium