Schisantherin A causes endothelium-dependent and -independent vasorelaxation in isolated rat thoracic aorta

Schisandra is a good choice in Traditional Chinese Medicine for the therapy of cardiovascular diseases, but whether it contains a or some specific component (s) responsible these effects are still unclear. In the present study, we explored whether Schisantherin A (SCA) causes vasorelaxation in isolated rat thoracic aorta.

We selected SCA, one of the main monomers of lignans from Schisandra, to examine its vasorelaxant effect on the isolated rat thoracic aorta and also exploited several tool inhibitors to probe its underlying mechanisms.

SCA produced relaxation concentration-dependently on the endothelium-intact (43.56 ± 2.17%) and endothelium-denuded thoracic aorta strips (18.76 ± 3.95%) pre-contracted by phenylephrine (PE). However, after treated with indomethacin or L-NAME, SCA showed only partial vasorelaxant effects. Whereas, this vasorelaxation by SCA was not changed with specific K⁺-channel inhibitors, i.e. barium chloride (BaCl₂), 4-aminopyridine (4-AP), tetraethylamine (TEA), and glibenclamide. SCA had no effect on the aorta strips pre-contracted by PE in neither Ca²⁺-free nor CaCl₂ conditions. But, in the Ca²⁺ free and high K⁺ environment, SCA partly abolished the vasocontraction induced by CaCl₂.

It was the first report to demonstrate that SCA had endothelium-dependent and -independent vasorelaxant effects on the isolated rat thoracic aorta, and the underlying mechanisms might be involved into its promoting the production of nitric oxide (NO) and prostacyclin (PGI₂), and inhibiting the voltage-dependent calcium channels (VDCCs) opening. This study may partially explain the use of Schisandra in cardiovascular diseases and facilitate further drug development as well.