Endocrine activity of pseudolaric acids A and B and their effects on sex hormones, prostaglandins, uteri, and fetuses

Two novel diterpendoids, pseudolaric acids A and B (PA, PB) first isolated from the root of Pseudolarix kaempferi Gorden in China, have been reported to possess significant antifertile activities in rats, hamsters, rabbits, and dogs. The present study demonstrated that neither PA nor PB had estrogenic and antiestrogenic activities, they also did not inhibit deciduous formation. When an effective dose of PB 30 mg.kg-1 was given on d 6 of pregnancy and the hormonal determinations were done on d 8 and d 12 of pregnancy, the progesterone, estradiol and prostaglandins E, F levels in plasma and the uterine prostaglandin E, F levels were not significantly reduced vs those of the control rats. The human uterus was used as the experimental material in vitro. PA and PB 200 micrograms.ml-1 cultural medium (McCoy's 5a medium) damaged only a part of the decidual and trophoblast cells. In partially depolarized isolated uterine smooth muscles of early pregnant rats, PA and PB caused a decline in the contractile tension. A low dose of PB 2 mg.kg-1.d-1 was given ig on d 6-12 of pregnancy in rats caused the body weight and the length of fetuses and the placental weight value significantly lower than those of the control. Thus, ischemia due to the vasoconstrictor effect is probably of great, and sometimes of supreme, importance.