Inhibition of Intracellular Calcium Elevation and Blunting of Vasopressor Response due to Serotonin by Ginkgolide B

Abstract

The vascular effects of each individual composition in the extract of Ginkgo biloba have not been clarified. In this work, we have investigated whether ginkgolide B (GKB), a terpene lactone component from Ginkgo biloba, modulates intracellular calcium ([Ca²⁺] _i ) of vascular smooth muscle cells (smc) and how it influences the vasopressor response in vitro caused by serotonin (5-HT). GKB (3.2 - 9.6 μM) selectively decreased serotonin-induced [Ca²⁺] _i elevations in cultured smc from bovine aorta in dose-dependent manner, while it had no effects on both resting [Ca²⁺] _i and potassium-elicited [Ca²⁺] _i elevations. On the other hand, GKB in a concentration of 3.2 - 9.6 μM moderately decreased the maximal pressor efficacy of serotonin by 14 - 45 % in rat mesenteric vascular beds, and the EC50 remained unchanged. The comparison study also showed GKB had no effects on noradrenaline-elicited pressor reactions. These results implicate that GKB may selectively inhibit serotonin-mediated [Ca²⁺] _i mobilization in vascular smc and non-competitively alleviate the vasopressor effect of serotonin in vitro.

Key words

Ginkgolides - Ginkgo biloba - Ginkgoaceae - 5-hydroxytryptamine - calcium - vasoconstriction - cultured cell - rat mesenteric vascular bed

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