Possible evidence that the herbal medicine shakuyaku-kanzo-to decreases prostaglandin levels through suppressing arachidonate turnover in endometrium.

The herbal medicine shakuyaku-kanzo-to has been used for the treatment of dysmenorrhea. We attempted to establish the effects of shakuyaku-kanzo-to on prostaglandin (PG) levels and the turnover of arachidonic acid in endometrial cells. Human endometrial cells isolated from proliferative-phase endometria were examined. Arachidonic acid reacylation activity was determined by [3H]arachidonic acid incorporation into endometrial cell phospholipid. Its deacylation rate was determined by both 3H-liberation from [3H]-arachidonic acid-labelled phospholipids and production of lyso-phospholipid. [3H]-PG levels were also analyzed. Shakuyaku-kanzo-to enhanced the rate and maximal level of arachidonic acid incorporation by 1.5-fold into phosphatidyl-ethanolamine and phosphatidylcholine. Degradation of the phospholipids to liberate arachidonic acid and lyso-derivatives was not affected by the shakuyaku-kanzo-to. Shakuyaku-kanzo-to decreased PG levels by approximately 50% of control. Because shakuyaku-kanzo-to stimulates arachidonic acid esterification to phospholipids, it seems likely that shakuyaku-kanzo-to depletes cellular free arachidonic acid with a consequent suppression of prostaglandin synthesis. Shakuyaku-kanzo-to may exert its action against dysmenorrhea through preventing prostaglandin production.