Baicalin and baicalein, constituents of an important medicinal plant, inhibit intracellular Ca2+ elevation by reducing phospholipase C activity in C6 rat glioma cells

Glial cells have a role in maintaining the function of neural cells. This study was undertaken to clarify the effects of baicalin and baicalein, flavonoids isolated from an important medicinal plant Scutellariae Radix (the root of Scutellaria baicalensis Georgi), on glial cell function using C6 rat glioma cells. Baicalin and baicalein caused concentration-dependent inhibition of a histamine-induced increase in intracellular Ca2+ concentrations ([Ca2+](i)). The potency of baicalein was significantly greater than that of baicalin. The noradrenaline- and carbachol-induced increase in [Ca2+](i) was also inhibited by baicalein and both drugs inhibited histamine-induced accumulation of total [H-3]inositol phosphates, consistent with their inhibition of the increase in [Ca2+](i). These results suggest that baicalin and baicalein inhibit [Ca2+](i) elevation by reducing phospholipase C activity. The inhibitory effects of baicalin and baicalein on [Ca2+](i) elevation might be important in the interpretation of their pharmacological action on glial cells, such as inhibition of Ca2+-required enzyme phospholipase A(2).