Rapid modulation by progesterone and tamoxifen of estradiol effects on nuclear histone acetylation in the uterus of the fetal guinea pig

The effect of estradiol, progesterone, tamoxifen, estradiol + progesterone or estradiol + tamoxifen on the ³H]acetylation of histones in the fetal uterus of guinea pig was studied. The fetuses were injected subcutaneously ‘in situ’ with the hormones or $\text{tamoxifen}\text{+}{}^3\text{H}\text{]}\text{acetate}$ alone. In 10 min, estradiol stimulated the acetylation of histone 10–12-times with respect to the control animals. Progesterone and tamoxifen blocked this effect. It is suggested that histone acetylation is an early step induced by estrogen action during intrauterine life and that progesterone and tamoxifen suppress this mechanism very effectively.