title: Effects of eugenol on resting tension of rat atria.
abstract: In cardiac and skeletal muscle, eugenol (μM range) blocks excitation-contraction coupling. In skeletal muscle, however, larger doses of eugenol (mM range) induce calcium release from the sarcoplasmic reticulum. The effects of eugenol are therefore dependent on its concentration. In this study, we evaluated the effects of eugenol on the contractility of isolated, quiescent atrial trabeculae from male Wistar rats (250-300 g; n=131) and measured atrial ATP content. Eugenol (1, 3, 5, 7, and 10 mM) increased resting tension in a dose-dependent manner. Ryanodine [100 µM; a specific ryanodine receptor (RyR) blocker] and procaine (30 mM; a nonspecific RyR blocker) did not block the increased resting tension induced by eugenol regardless of whether extracellular calcium was present. The myosin-specific inhibitor 2,3-butanedione monoxime (BDM), however, reversed the increase in resting tension induced by eugenol. In Triton-skinned atrial trabeculae, in which all membranes were solubilized, eugenol did not change resting tension, maximum force produced, or the force vs pCa relationship (pCa=-log [Ca2+]). Given that eugenol reduced ATP concentration, the increase in resting tension observed in this study may have resulted from cooperative activation of cardiac thin filaments by strongly attached cross-bridges (rigor state).
authors.affiliation: Departamento de Fisiologia, Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: R R
authors.initials: RR
authors.lastname: Olivoto
authors.affiliation: Departamento de Fisiologia, Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: C E N
authors.initials: CE
authors.lastname: Damiani
authors.affiliation: Departamento de Fisiologia, Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: I
authors.initials: I
authors.lastname: Kassouf Silva
authors.affiliation: Departamento de Fisiologia, Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: M S
authors.initials: MS
authors.lastname: Lofrano-Alves
authors.affiliation: Departamento de Fisiologia, Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: M A
authors.initials: MA
authors.lastname: Oliveira
authors.affiliation: Departamento de Fisiologia, Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: R T H
authors.initials: RT
authors.lastname: Fogaça
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology*; D005054:Eugenol / Q000008:administration & dosage / Q000494:pharmacology*; D056966:Excitation Contraction Coupling / Q000187:drug effects*; D006325:Heart Atria / Q000187:drug effects*; D066298:In Vitro Techniques; D008156:Luciferases; D008297:Male; D053580:Muscle Strength / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects*; D011343:Procaine / Q000494:pharmacology; D017208:Rats, Wistar; D012433:Ryanodine / Q000494:pharmacology
chemical_list: D000779:Anesthetics, Local; D012433:Ryanodine; D005054:Eugenol; D011343:Procaine; D000255:Adenosine Triphosphate; D008156:Luciferases; D002118:Calcium