Localization of the iron transport glycoprotein, uteroferrin, in the porcine endometrium and placenta by using immunocolloidal gold.

Uteroferrin, a glycoprotein implicated in transplacental iron transport in the pig, has been localized within the porcine uterus during mid pregnancy by using immunocolloidal gold labeling of sectioned material. In the endometrium where uteroferrin is synthesized, it was located exclusively in the non-ciliated cells of the glandular epithelium where it appeared to follow a common route of secretory glycoprotein from the cell (i.e., rough endoplasmic reticulum----Golgi----condensing vacuoles----secretory granules). Uteroferrin was present in the lumen of the glands and overlying placental areolae and in the large absorptive chorionic epithelial cells of the areolae. The latter cells contained numerous small vesicles and tubules as well as large endocytotic vacuoles. All these structures contained uteroferrin and are probably involved in translocating the glycoprotein in intact form from the uterine lumen to the blood capillaries draining the placenta.