The vaso-contractile action of zooxanthellatoxin-B from a marine dinoflagellate is mediated via Ca2+ influx in the rabbit aorta

Takahiro Moriya, Ken Ichi Furukawa, Hideshi Nakamura, Akio Murai, Yasushi Ohizumi

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

We previously showed that zooxanthellatoxin-B, isolated from dinoflagellate, caused a sustained contraction of the aorta in an external Ca2+-dependent manner. To clarify the role of Ca2+ in this action, we examined the effects of zooxanthellatoxin-B as well as a depolarizing stimulus (60 mM KCl), using the simultaneous recording for cytosolic Ca2+ level (fura-2) and developed tension in the rabbit aorta. KCl (60 mM) elicited a rapid cytosolic Ca2+ elevation followed by a pronounced contraction, and time required for half-maximum contraction was 2 min. Zooxanthellatoxin-B caused an increase in cytosolic Ca2+ followed by a gradual contraction, with a time for half-maximum contraction of 5-10 min in a concentration-dependent manner. We found a strong correlation between Ca2+ elevation and the contraction in zooxanthellatoxin-B action. In a Ca2+-free solution, zooxanthellatoxin-B caused neither the contraction nor the increase in cytosolic Ca2+. Furthermore, both pre- and post-treatment with verapamil, a voltage-operated Ca2+-channel blocker, partially suppressed both an increase in cytosolic Ca2+ and the contraction by zooxanthellatoxin-B. Zooxanthellatoxin-B-induced contraction was also inhibited by other voltage-operated Ca2+-channel blockers: nifedipine or diltiazem. These results suggest that zooxanthellatoxin-B-elicited contraction is caused by a Ca2+ influx into the smooth muscle cells, partially via voltage-operated Ca2+ channels.

Original languageEnglish
Pages (from-to)1030-1035
Number of pages6
JournalCanadian Journal of Physiology and Pharmacology
Volume79
Issue number12
DOIs
Publication statusPublished - 2001 Dec 1

Keywords

  • Ca imaging
  • Contraction
  • Rabbit aorta
  • Voltage-operated Ca-channels
  • Zooxanthellatoxin

ASJC Scopus subject areas

  • Physiology
  • Pharmacology
  • Physiology (medical)

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