We investigated the potential direct effects of Tokishakuyakusan (TS) on progestin [progesterone and 20 α-hydroxyprogesterone (20 α-OH-P)] and cyclic adenosine-3', 5'-monophosphate (cAMP) production in cultured rat luteal cells. In addition, we examined whether TS regulates the inhibitory effects of pituitary adenylate cyclase-activating polypeptide (PACAP), a newly found peptide, on luteinizing hormone (LH)-stimulated progesterone production. TS significantly stimulated progesterone, but not 20α-OH-P, production and cAMP accumulation through 24 hours of culture. PACAP-38 significantly elevated progesterone, 20α-OH-P and cAMP levels at all concentrations studied. On the other hand, PACAP-38 inhibited the production of progesterone and the accumulation of cAMP enhanced by LH, while the ratio of progesterone to 20α-OH-P was significantly decreased by PACAP-38 + LH. Concomitant treatment with TS and PACAP-38 + LH increased the ratio of progesterone to 20α-OH-P more than with PACAP-38 + LH. The present data have demonstrated that TS stimulates progesterone production in rat luteal cells, reconfirming our previous evidence that TS stimulates luteal steroidogenesis. The data further suggest that TS tends to attenuate PACAP's inhibition of LH-stimulated progesterone production, suggesting a luteotrophic effect within the corpus luteum.
Effect of pituitary adenylate cyclase-activating polypeptide (PACAP) on progestin biosynthesis in cultured granulosa cells from rat ovary and expression of mRNA encoding PACAP type IA receptor