An estrogen-dependent endogenous peroxidase in uterine epithelial cells of neonatal rats.

The endogenous peroxidase synthesis within the uterine epithelial cells during the neonatal period of female rats following the . estrogen stimulation was studied by means of the histochemical method, to elucidate the critical period in the initiation of its synthesis and the relation between the peroxidase synthesis and the morphological alteration within these cells. The critical period was approximately 6 days of age, and it appeared that the period was earlier than that reported in previous biochemical investigations. The period is well in accord with the time when the quantity of estrogen receptor become sufficient to be functionally valid. It is suggested on this basis that the histochemical detection of intracellular peroxidase activity is more practical for clarification of estrogen-sensitivity of the tissue than the quantitative measurement of estrogen receptor in the neonatal rats. Ultrastructural findings revealed that the initial appearance of intracytoplasmic estrogendependent peroxidase activity was most closely correlated to the developmental status of the rough endoplasmic reticulum and that the rough endoplasmic reticulum, the Golgi apparatus and the apical vesicles were involved in the process of peroxidase synthesis and intracytoplasmic transport. It appeared that peroxidase synthesis was a good marker of estrogen-mediated cell growth, although the exact role of peroxidase in the uterine epithelial cells has been still uncertain. 311