title: Coupling of store-operated Ca++ entry to contraction in rat aorta.
abstract: The purpose of this study was to test whether the elevated intracellular Ca++ level ([Ca++]i) resulting from store-operated Ca++ entry was associated with vascular smooth muscle contraction. Cyclopiazonic acid (CPA), a selective inhibitor of sarcoplasmic reticulum Ca(++)-ATPase, concentration-dependently (1-10 microM) elevated [Ca++]i in rat aorta, as indicated by an increase in the fura-2 340/380 ratio. Simultaneous measurement of contraction demonstrated that 1 and 10 microM CPA induced insignificant and variable amounts of contraction, respectively. Verapamil (10 microM) had relatively little effect on the 1 and 10 microM CPA-elevated [Ca++]i. In contrast, Ni++ (0.1 mM), in the presence of verapamil, abolished the 1 microM CPA-elevated [Ca++]i. Ni++ (0.1 mM) also partially decreased the 10 microM CPA-elevated [Ca++]i and, furthermore, abolished the associated contraction. A higher Ni++ concentration (1 mM) abolished the 10 microM CPA-elevated [Ca++]i that remained after verapamil and 0.1 mM Ni++. Phorbol dibutyrate (10 nM), a protein kinase C activator, potentiated contractions to 1 and 10 microM CPA in the presence of verapamil. Ni++ (0.1 mM) abolished the enhanced contractions, and decreased the elevated [Ca++]i. These results suggest that 1) elevated [Ca++]i due to store-operated Ca++ entry is dissociated from contraction; 2) the elevated [Ca++]i is restricted to at least two noncontractile compartments that can be differentiated by their relative sensitivities to blockade by low (0.1 mM) and higher (1 mM) Ni++ concentrations, and 3) [Ca++]i elevation within the compartment sensitive to blockade by 0.1 mM Ni++ can be coupled to contraction via protein kinase C activation.
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati, Ohio, USA.
authors.forename: M
authors.initials: M
authors.lastname: Tosun
authors.forename: R J
authors.initials: RJ
authors.lastname: Paul
authors.forename: R M
authors.initials: RM
authors.lastname: Rapoport
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D006873:Hydroquinones / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008297:Male; D009532:Nickel / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction; D014700:Verapamil / Q000494:pharmacology
chemical_list: D006873:Hydroquinones; D007211:Indoles; C019359:2,5-di-tert-butylhydroquinone; D015240:Phorbol 12,13-Dibutyrate; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D009532:Nickel; D014700:Verapamil; D011493:Protein Kinase C; D002118:Calcium; C000543:cyclopiazonic acid