Localization of Uterine Peroxidase Activity in Estrogen-Treated Rats

Abstract

Uterine peroxidase activity is known to increase dramatically following estrogen treatment and to be sensitive to modulation by substances which modify the uterine responses to estrogen. However, it is not clear how much of the uterine peroxidase originates within the uterine epithelium and how much may be due to eosinophils that migrate into the uterus after estrogen treatment. We have addressed this problem by comparing the distribution of rat uterine peroxidase by biochemical and histochemical methods. Histochemical examination of frozen uterine sections, as well as biochemical analysis of separated uterine tissue components, demonstrates that the peroxidase is localized predominantly in cells of the endometrial stroma and myometrium. When the uterine peroxidase response to estrogens was inhibited to variable degrees by concomitant administration of progesterone, dexamethasone, the synthetic antiestrogen Cl628, or actinomycin D, parallel decreases in the uterine eosinophil response were observed. To determine the quantity of uterine eosinophil peroxidase directly, the peroxidase content of purified eosinophils was measured. With this specific activity and the estimated number of uterine eosinophils, the total eosinophilic peroxidase of one uterine horn was calculated and found to be quantitatively the same as the total biochemically assayed enzyme of the contralateral horn for various uteri. Solubilized peroxidase of the uterus and of eosinophils could not be distinguished by sedimentation analysis. These experiments indicate that while the uterine epithelium contains estrogen-inducible peroxidase, virtually all of the peroxidase activity extracted from estrogen-stimulated uteri originates in the uterine eosinophils.