Is Guanosine-5'-triphosphate Involved in Calcium-Activation of Contractile Proteins in Vascular Smooth Muscle?

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Isometric tension was measured to investigate the effects of guanosine-5''-triphosphate (GTP) on the run-down of myofilament Ca<SUP>2+</SUP> sensitivity in isolated rat mesenteric arteries permeabilized with β-escin. The Ca<SUP>2+</SUP> sensitivity assessed by the EC<SUB>50</SUB> value for the Ca<SUP>2+</SUP> (0.1-100μM)-tension relationship progressively runs down in the control strips, while it was well-preserved for 5-successive Ca<SUP>2+</SUP> applications in the presence of GTP (50 μM); no significant difference was found in the Ca<SUP>2+</SUP> sensitivity observed with the 1st Ca<SUP>2+</SUP> application between the control and GTP-treated strips. Guano sine-5''-(2-Ο-thio) diphosphate (GDPβS, 100 μM) significantly decreased the Ca<SUP>2+</SUP> sensitivity with the 1st Ca<SUP>2+</SUP> application and eliminated the run-down of Ca<SUP>2+</SUP> sensitivity. GTP (3 -150 μM), applied to the strips submaximally precontracted with Ca<SUP>2+</SUP>, had a little effect on the Ca<SUP>2+</SUP> contractions in the early stage of experiments, but dramatically enhanced the Ca <SUP>2+</SUP> contractions in their later stage; its latter effect was mimicked by guanosine-5''-(3-Ο-thio) triphosphate (GTPγS) and reversed by GDP13S (100 μM). The results suggest: 1) loss of endogenous GTP following permeabilization is involved in the run-down of Ca<SUP>2+</SUP> sensitivity; and 2) activation of G-proteins is involved in Ca<SUP>2+</SUP>-activation of contractile proteins.

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  • The Japanese journal of pharmacology

    The Japanese journal of pharmacology 75(1), 1-12, 1997-09-01

    The Japanese Pharmacological Society

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各種コード

  • NII論文ID(NAID)
    10008679573
  • NII書誌ID(NCID)
    AA00691188
  • 本文言語コード
    ENG
  • 資料種別
    ART
  • ISSN
    00215198
  • NDL 記事登録ID
    4307639
  • NDL 雑誌分類
    ZS51(科学技術--薬学)
  • NDL 請求記号
    Z53-D199
  • データ提供元
    CJP書誌  NDL  J-STAGE 
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