title: Thapsigargin does not affect phenylephrine-induced contractions in the anococcygeus muscle of rats.
abstract: 1. The aims of the present study were to investigate the contribution of intracellular calcium and to evaluate the effect of the antagonists of the intracellular calcium stores, thapsigargin and [8-(Diethylamino)-octyl-3,4,5-trimethoxybenzoate, HC1] TMB-8, on phenylephrine-stimulated contractions of rat anococcygeus smooth muscle, using functional studies. 2. Phenylephrine induced concentration-related contractions in both 2.5 mM Ca2(+)-free EGTA media. 3. In Ca2(+)-free media phenylephrine stimulated successive contractions, and the contractile response was abolished only after approximately 26 stimulations. 4. In Ca2(+)-free media, after incubation with 10 microM TMB-8 for 30 min, phenylephrine induced concentration-response curves that shifted to the right. The EC50 values were not changed, and the maximum contractile response was reduced by 39.2 +/- 7.6% in relation to phenylephrine-stimulated responses in absence of TMB-8. 5. Thapsigargin (1 microM) did not alter phenylephrine-stimulated contractions in Ca2(+)-free media. 6. These results indicate that intracellular Ca2+ plays an important role on phenylephrine-stimulated contractions on rat anococcygeus muscle and that the phenylephrine-sensitive intracellular Ca2+ store is not sensitive to thapsigargin.
authors.affiliation: Laboratory of Pharmacology, College of Pharmaceutical Sciences, University of Sao Paulo, Ribeirao Preto, Brazil.
authors.forename: C
authors.initials: C
authors.lastname: da Silva
authors.forename: L M
authors.initials: LM
authors.lastname: Bendhack
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D010656:Phenylephrine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D019284:Thapsigargin / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D010656:Phenylephrine; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D002118:Calcium