Mun-Chual Rho, Norimichi Nakahata and Yasushi Ohizumi (*)
Department of Pharmaceutical Molecular Biology, Faculty of Pharmaceutical
Sciences, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980, Japan
(*) To whom correspondence should be addressed.
Abstract: The marine toxin zooxanthellatoxin-A (ZT-A) and the
Ca2+ ionophore ionomycin caused aggregation in rabbit platelets. While ZT-A-induced
platelet aggregation was inhibited by indomethacin, ionomycin-induced aggregation
was potentiated by the drug. In contrast, both ZT-A- and ionomycin-induced
accumulations of thromboxane B2 (TXB2), a stable metabolite of thromboxane
A2 (TXA2), were completely inhibited by indomethacin. 12S-Hydroxyeicosatetraenoic
acid (12-HETE), which could be accumulated in the presence of indomethacin,
inhibited ZT-A-induced aggregation, but it potentiated the ionomycin-induced
one. These results suggest that the different effects of indomethacin may
be attributed to the distinct effects of 12-HETE on ZT-A- and ionomycin-induced
platelet aggregations.
Keywords: Zooxanthellatoxin-A, Ionomycin, 12S-Hydroxyeicosatetraenoic
acid