Program

PO3-10-26

The mechanisms of loganin-induced vasodilatation in rat mesenteric artery

[Speaker] Seiichiro Nishida:1,2
[Co-author] Katsuharu Tsuchida:2, Hiroyasu Satoh:3
1:Internal Medicine, Hanna Central Hospital, Japan, 2:Doshisha Women's College, Japan, 3:Shitennoji University, Japan

Aims: Loganin is a kind of iridoid glycoside compound isolated from Fructus corni . The mechanism of vasodilating actions induced by loganin was investigated using rat mesenteric artery.
Main Methods: Ring strips (1 mm) of rat mesenteric artery were used. The specimens were kept at 37 .5 °C in Krebs-Henseleit solution oxygenated with 95% O2 and 5% CO2.
Key Findings: Loganin (0.1 to 100 µM) dilated the contraction induced by norepinephrine (1 µM) in a concentration-dependent manner.At 100 µM, loganin dilates the contraction by 82.9 ± 3.4 %. The loganin-induced vasodilatation was slightly attenuated by the pretreatment of 100 µM L-NG-nitro arginine methyl ester (L-NAME), but resistant to the indomethacin (20µM). The vasodilatation at 100 µM was attenuated to 71.9 ± 4.8% (n = 6, p>0.05) by L-NAME. The combination of L-NAME and indomethacin attenuated the loganin-induced vasodilatation as same as L-NAME alone. However, the residual vasodilatation in the presence of L-NAME and indomethacin was strongly and significantly attenuated by additional pretreatment of 18α- glycyrrhetinic acid (gap junction inhibitor).The combined pretreatment of 18α- glycyrrhetinic acid (100 µM), L-NAME and indomethacin reduced the vasodilatation at 100 µM loganin to 49.9 ± 3.7 % (n=9, p> 0.01). Endothelium removal significantly attenuated the vasodilatation to the same extent as the combined pretreatment of 18α- glycyrrhetinic acid, L-NAME and indomethacin. As well, endothelium removal significantly attenuated the vasodilatation to the same extent as the combined pretreatment of 18α- glycyrrhetinic acid, L-NAME and indomethacin.
Significance: These results indicate that loganin dilates the mesenteric artery via endothelium-dependent mechanisms, and the dilatation is mainly mediated by gap junction closely involved with endothelium-derived hyperpolarizing factor (EDHF).

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