Specificities in the synthesis of a cytoplasmic estrogen-induced uterine protein

The earliest known induction by estrogen of a specific uterine protein is that of the ‘induced protein’ (IP) of Gorski and colleagues, which is demonstrable within 40 min after treatment. We found that this protein is not restricted to the rat; it was detected in the uterus of prepuberal C3H/eB and SWR mice, l h after injection of 4 μg of estradiol-17β. IP was also induced in vivo by the non-steroidal plant estrogens genistein (1250 μg/rat) and coumestrol (300 μg/rat) and the synthetic estrogen diethylstilbestrol (5 μg/rat). We found no significant increase in the stimulation of the rate of IP synthesis by estrogen in uteri from either 10- or 20-day-old rats on subsequent treatment with actinomycin D, indicating that there was no superinduction of IP, despite a previous claim.