Cyclic changes in human endometrial surface glycoproteins: a quantitative histochemical study.

We used histochemical methods specific for carbohydrates on accurately timed endometrial biopsies to examine changes in quantity or electronegativity of the endometrium's luminal glycocalyx through the menstrual cycle in normal fertile women. Electronegative glycocalyx was detectable light-microscopically throughout the menstrual cycle. On the third day after the luteinizing hormone peak, a significant increase (P = 0.005) in endometrial surface glycocalyx was evident along with the appearance, in endometrial glands, of material having the staining properties of acid mucus glycoprotein (MGP), which implies that after this material's production by the glands or by the surface epithelium, it becomes adsorbed onto the surface glycocalyx. This phenomenon was accompanied by an apparent decrease in glycocalyceal electronegativity as indicated by a shift from high iron diamine (pH 1.0) to alcian blue (pH 2.5) staining reactivity. Because the timing of the appearance of endometrial moderately acid MGP coincides with or precedes the time that the early fertilized embryo enters the endometrial cavity, a role for the MGP in embryo nutrition or in implantation is suggested.