[Effects of tyrosine alone and tyrosine in combination with RU486 on early pregnancy in mice and the mechanism of action].

Treatment with tyrosine at the dosage of 85 mg.kg-1 on day 6-8 of gestation did not have significant effect to terminate early pregnancy in mice. Tyrosine combined with RU486 was shown to have a synergistic effect to terminate early pregnancy. Tyrosine 170 mg.kg-1 on day 6-10 of gestation significantly decreased the concentration of serum progesterone in early pregnant mice. Further study with luteal cells in rats showed that tyrosine 50 micrograms.ml-1 inhibited hCG-induced progesterone production when used alone, and inhibited basal production when used together with (+) PG05. These results suggest that the inhibiting effect of tyrosine on steroidogenesis may contribute to the termination of early pregnancy.