Antagonism of saikosaponin-induced prostaglandin E-2 release by baicalein in C6 rat glioma cells

There are several Kampo medicines (Chinese herbal medicines) containing bot h Bupleuri Radix and Scutellariae Radix, which are used for the treatment o f inflammation. Saikosaponins are derived from Bupleuri Radix, and baicalei n is from Scutellariae Radix, The present study was undertaken to investiga te the pharmacological interaction of saikosaponin b1 and baicalein in pros taglandin E-2 (PGE(2)) release from C6 rat glioma cells in vitro, Saikosapo nin a, bl and d potently stimulated PGE(2) release, while saikosaponin b2 a nd c moderately stimulated PGE(2) release. Saikosaponin b1 caused an irreve rsible elevation of intracellular Ca2+ concentration, which was eliminated by removing extracellular Ca2+. On the other hand, baicalein inhibited saik osaponin b1-induced PGE(2) release in a concentration-dependent manner. The se results suggest that saikosaponins are activators of PGE(2) release, and baicalein is one of the functional inhibitors of PGE(2) release by saikosa ponins.