Oestrogenic stimulation of macromolecular synthesis is correlated with nuclear hormone-receptor complex in neonatal rat uterus.

Abstract

THE ability of oestrogen to elicit pronounced physiological responses in the mammalian uterus depends on specific receptor proteins that recognize and retain the hormone1–3. The formation of cytoplasmic oestradiol-receptor complexes and their transformation to nuclear complexes seem to be an important prelude to the stimulation of RNA synthesis in the organ2,3. Since a cytoplasmic oestradiol-receptor complex is present in the uterus of the neonatal rat 1 d after birth4, we have investigated whether the uterus of the neonatal rat can transform the cytoplasmic hormone-receptor complex to the nuclear complex, as described for the immature or older animal1,3. Because relatively little is known about the growth responses of the neonatal uterus to oestrogen, we have examined quantitatively the synthesis and concentrations of DNA and protein in the control and hormone-stimulated uterus, as a function of time after birth. It has been reported5 that oestrogen administered 24 h before death to rats less than 15 d old does not stimulate uterine weight or macro-molecular synthesis.