title: Extracellular Ca2+-dependent contractile action of phorbol 12,13-dibutyrate on gall bladder from guinea pig.
abstract: The effects of phorbol 12,13 dibutyrate (PDBu) on the isometric tone of gall bladder strips isolated from guinea pig were investigated. PDBu caused the development of a contractile force at concentrations of 5 nM to 1 microM, which was abolished by staurosporine (30 nM). The contraction was completely inhibited in Ca2+-free solution and by pretreatment with verapamil (1 microM) or nifedipine (1 microM). A lower concentration of PDBu (1 nM) potentiated the contractile response to KCl: it increased the sensitivity, but not the reactivity of KCl-induced contraction. Ca2+-induced contraction in the solution with 15 mM KCl was significantly augmented by the pretreatment with 1 nM PDBu. However, PDBu (1 nM) affected neither Ca2+-induced contraction in the presence of Ca2+ ionophore A23187 (0.7 microM) and verapamil (1 microM) nor Ba2+-induced contraction in the Ca2+-free solution. These results suggest that activation of protein kinase C induces completely extracellular Ca2+-dependent contraction by activating the voltage-dependent Ca2+ channels in gall bladder of guinea pig.
authors.affiliation: Department of Hygiene, Hyogo College of Medicine, Nishinomiya, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Masui
authors.forename: I
authors.initials: I
authors.lastname: Wakabayashi
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004357:Drug Synergism; D005704:Gallbladder / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D006168:Guinea Pigs; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D015240:Phorbol 12,13-Dibutyrate; D011189:Potassium Chloride; D014700:Verapamil; D019311:Staurosporine; D009543:Nifedipine; D002118:Calcium