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 μg·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.