The effect of magnesium lithospermate B purified from Salviae Miltiorrhizae Radix on the kinin-prostaglandin E2 system was investigated using kidney slices and isolated kidney microsomes. Magnesium lithospermate B markedly increased the amount of thiobarbituric acid-reactive substances produced by incubation of arachidonic acid in renal slices. Enhancement of arachidonic acid-mediated oxygenation of 1,3-diphenylisobenzofuran was also observed in renal microsomes from rats treated with magnesium lithospermate B, indicating an increase of prostaglandin biosynthesis. Furthermore, magnesium lithospermate B significantly increased the synthesis of prostaglandin E2 in renal slices, but the magnesium lithospermate B-mediated response was blunted with kinin antagonist. On the basis of the above results, it is apparent that magnesium lithospermate B exerts an influence on the prostaglandin system via kinin receptors.