Distribution of peroxidase and granulocytes in the human uterus.

A variety of uterine cell types demonstrate endogenous peroxidase activity. Ultracytochemical localization, biochemical assays, and uterine granulocyte counts were used to characterize peroxidase activity in various regions of the human uterus and cervix during the menstrual cycle and during the postmenopausal period. Previous studies of rat uteri, using electron microscopy and biochemical assays, have shown that endometrial peroxidase is induced by estrogenic stimulation (Anderson, De Sombre, and Kang, J Cell Biol 64:668, 1975; and Biol Reprod 16:409, 1977). Tissue samples from four regions of the human uterus and one sample from the endocervix were processed for ultrastructural cytochemistry, biochemical assay, and histology. Endogenous peroxidase activity was identified with electron microscopy in the endoplasmic reticulum of endometrial epithelial cells lining four regions of the uterine cavity; the isthmus, body (2), and fundus, of some proliferative phase (2 of 6), all secretory phase (4 of 4) and all postmenopausal (3 of 3) endometria. Peroxidase activity was not demonstrable in endocervical epithelial cells. Endogenous peroxidase activity was also identified in the cytoplasmic granules of uterine eosinophils and neutrophils and in the endoplasmic reticulum of mast cells. These uterine granule-containing cells, identified with special stains in the histologic sections, were quantitated. Approximately 80% of these "uterine granulocytes" from normal uteri without intrauterine devices were neutrophils. In women of reproductive age the uterine granulocytes, although present throughout the menstrual cycle, were most numerous in the endocervix and lower uterine segment. The highest biochemical assays of peroxidase activity were also obtained in the cervix and lower uterine segment. Uterine granulocyte counts varied directly with biochemical assays of peroxidase activity indicating that they were a major determinant of biochemical peroxidase activity. Endometrial epithelial peroxidase is anatomically and temporally well placed to function as an important adjunct in maintaining a mucosal barrier to microorganisms.