Carbohydrates mediate the adherence of hamster sperm to oviductal epithelium

The lower isthmus of the mammalian oviduct appears to serve as a reservoir for sperm that are retained by adherence to the epithelium. By inhibiting sperm binding within excised hamster oviducts and making use of carbohydrate probes, we have characterized the adherence of sperm in the reservoir and established a potential biochemical mechanism for the adherence and release of sperm. Fetuin and its terminal sugar, N-acetylneuraminic acid, interfered with the adherence of sperm to the oviductal epithelium. Labeled fetuin bound to the acrosomal region of fresh epididymal sperm, but not hyperactivated sperm, which have previously been reported to release from epithelial binding. Western blots labeled with fetuin and sialic acid-recognizing lectins identified proteins at several molecular masses that are candidates for the sperm surface component involved in adherence. Labeling of some of these candidates was reduced in samples from hyperactivated sperm. These results indicate that a sialylated oligosaccharide similar to that found on fetuin may be recognized by a sperm surface component and mediate binding to the oviductal epithelium. Release may be accomplished by loss or modification of the component during capacitation or hyperactivation.