Abstract: Treatment of pseudopregnant rats with GAA at the dosage of 40 or 80 mg/kg for 5 days caused a decrease of cytoplasmic protein and estrogen receptor level per uterus, even though the estrogen receptor concentration per mg protein did not show significant change between the control and treated animals.Saturation analysis showed that in immature rats GAA at 40 mg/kg for 8 days reduced the amount of estrogen receptor per uterus. Bmax in the control and treated groups Was found by Scatchard analysis to be 432.0 and 358.8 fmol/uterus respectively. Kd was calculated to be 1.04×10^-10 and 1.09×10^-10 mol respectively.The IC₅₀ of GAA was shown to be 7.0 × 10^-5 mol indicating that GAA at high concentrations was capable of inhibiting the binding of ³H-estradiol with the receptor.PG 05,however, was found to have no effect on the level of protein and estrogen receptor per uterus or per mg protein.