title: Effects of U46619 on intracellular Ca++ concentration and tension in human umbilical artery.
abstract: OBJECTIVE
  The aim was to examine the effects of U46619, a thromboxane A2 analog, on intracellular Ca++ concentration and tension in human umbilical artery.
  
  
  METHODS
  By means of front-surface fluorometry and human umbilical arterial strips loaded with fura-2 we simultaneously measured intracellular Ca++ concentration and tension.
  
  
  RESULTS
  In the presence of extracellular Ca++ (1.25 mmol/L), U46619 elevated intracellular Ca++ concentration and tension in a concentration-dependent manner. Oscillations of both intracellular Ca++ concentration and tension were evident in many cases. In the absence of extracellular Ca++ U46619 induced a transient elevation of intracellular Ca++ concentration that was associated with a transient increase and a sustained tension. At any given intracellular Ca++ concentration level the tension induced by the cumulative application of extracellular Ca++ during depolarization with high external K+ in the presence of U46619 was greater than that in the absence of this drug; thus the intracellular Ca++ concentration-tension relationship in the presence of U46619 shifted to the left.
  
  
  CONCLUSIONS
  The tension developed by U46619 depends both on an influx of Ca++ from the extracellular space and on release of intracellular Ca++, and U46619 increased Ca++ sensitivity of the contractile apparatus.
authors.affiliation: Division of Molecular Cardiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Toyofuku
authors.forename: J
authors.initials: J
authors.lastname: Nishimura
authors.forename: S
authors.initials: S
authors.lastname: Kobayashi
authors.forename: H
authors.initials: H
authors.lastname: Nakano
authors.forename: H
authors.initials: H
authors.lastname: Kanaide
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000704:Analysis of Variance; D002118:Calcium / Q000378:metabolism*; D005260:Female; D005470:Fluorometry / Q000379:methods; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D011247:Pregnancy; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology*; D013928:Thromboxane A2 / Q000031:analogs & derivatives* / Q000494:pharmacology; D014469:Umbilical Arteries / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D011450:Prostaglandin Endoperoxides, Synthetic; D014662:Vasoconstrictor Agents; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D002118:Calcium