Estrogen induced peroxidase secretion from the endometrial epithelium: a possible function for the luminal enzyme

Estrogen induced peroxidase (EIP) activity revealed as a diaminobenzidine-H2O2 product in electron micrographs is apparent within cisternae of the RER and in large dilated apical vesicles, of which only a few have been seen to open into the uterine lumen. EIP activity is infrequently present in the trans cisternae of the rather diminutive Golgi complex in uterine epithelial cells from 12-72 h after treatment with estrogen. EIP activity is, however, prominent on the surface of microvilli of epithelial cells and as deposits in the lumen. Desalted uterine fluid (72 h) isolated by rotofor (Biorad) and analysed on isoelectric focusing gels that were stained with the diaminobenzidine-H2O2 reaction, reveal the existence of at least 6 peroxidase isoelectric variants with isoelectric points between pI 3.5 and pI 5.0. In similar preparations doubly-stained by diaminobenzidine-H2O2 and silver, peroxidase positive bands are enhanced, along with other isoelectric variants in the acidic pI range. In SDS-PAGE preparations, five prominent proteins ranging from 29-115 kD are present in 72 h uterine fluid. Luminal EIP coats the surface microvilli of the reproductive tract cells, and of viable spermatozoa incubated in uterine fluid. Peroxidase coated bacteria appear to be in the process of decay, and enzyme activity is present on the surface of most spermatozoa. It is not yet determined if EIP has bactericidal, spermicidal or capacitation functions.