Peroxidase in estrogen-sensitive tissues

The partial purification and characterization of a peroxidase that can be induced rapidly in immature rat uteri by physiological doses of estradiol has been described together with the evidence that it is produced in situ and is distinct from eosinophil peroxidase. Cycloheximide which blocks the increase in peroxidase activity brought about by estrogens was used to determine the half-life (about 4 hr) of the induced uterine enzyme. The subcellular localization of the enzyme after treatment of immature rats with estrogen has been examined by sucrose density gradient centrifugation and the peroxidase shown to be localized in particles sedimenting more rapidly than mitochondria (succinic dehydrogenase marker) or lysosomes (acid phosphatase marker) The peroxidase activity in 47 DMBA-induced mammary tumors has also been determined and the properties of this enzyme have been compared to those of lactoperoxidase. The possible role of peroxidase in these two estrogen-sensitive tissues is discussed and evidence provided against the proposal that this enzyme is always associated with growth processes.