Angiotensin II, a unique vasoactive agent dissociates myosin light chain phosphorylation from contraction

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Author(s)

    • HIRANO Takashi
    • Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
    • KANEDA Takeharu
    • Laboratory of Veterinary Pharmacology Nippon Veterinary and Life Science University, Kyonan-cho 1-chome, Musashino, Tokyo 180-862, Japan
    • OZAKI Hiroshi
    • Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
    • HORI Masatoshi
    • Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan

Abstract

<p>Angiotensin II (100 nM) induced bi-phasic increases in cytosolic Ca<sup>2+</sup> level ([Ca<sup>2+</sup>]<sub>i</sub>) through the activation of angiotensin II type 1 receptor. Pharmacological examinations using 10 <i>µ</i>M verapamil, 30 <i>µ</i>M La<sup>3+</sup>, and 1 <i>µ</i>M thapsigargin indicated that the first phase of the [Ca<sup>2+</sup>]<sub>i</sub>-increase was mediated by Ca<sup>2+</sup> release from sarcoplasmic reticulum (SR) and Ca<sup>2+</sup> influx independently of voltage dependent Ca<sup>2+</sup> channel (VDC). In contrast, the second phase of [Ca<sup>2+</sup>]<sub>i</sub>-increase was mediated by Ca<sup>2+</sup> influx through VDC. Although both [Ca<sup>2+</sup>]<sub>i</sub> and myosin light chain (MLC)-phosphorylation at the first phase was apparently exceeded the threshold for contraction as estimated by high K<sup>+</sup>-induced responses, there was no appreciable contraction, indicating the dissociation between MLC phosphorylation and force during this phase. In contrast, the second phase of [Ca<sup>2+</sup>]<sub>i</sub> was associated with the increases in both MLC phosphorylation and force. These results suggest that angiotensin II is a unique agonist which dissociates MLC-phosphorylation from muscle force during the Ca<sup>2+</sup> releases from SR.</p>

Journal

  • Journal of Veterinary Medical Science

    Journal of Veterinary Medical Science 80(2), 219-224, 2018

    JAPANESE SOCIETY OF VETERINARY SCIENCE

Codes

  • NII Article ID (NAID)
    130006339672
  • Text Lang
    ENG
  • ISSN
    0916-7250
  • Data Source
    J-STAGE 
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