Specific Inhibition of Equine Sperm Binding to Oviductal Epithelium1

Sperm binding to epithelium could play a role in the formation of the reservoir of sperm in the oviduct, but the nature of the binding interaction is poorly understood. The present experiment was designed to determine whether or not equine sperm binding to oviductal epithelium involves a specific lectin-like interaction. A series of carbohydrates were tested for their ability to block sperm binding in vitro. Oviducts were collected at an abattoir from mares with preovulatory follicles (> 35 mm). Mucosal epithelium obtained from the oviducts was cultured in medium M-199 for 1–4 days. Within 24 h it formed everted tubes with the ciliary activity evident on the surface. Ejaculated stallion sperm were washed in calcium-free Tyrode’s medium and incubated for 10 min with potential binding inhibitors; then oviductal epithelium was added. After 50 min, the number of bound sperm/0.1 mm2 of epithelial surface area was determined. Of the 11 carbohydrates tested, asialofetuin and its terminal residue galactose significantly inhibited binding (asialofetuin 9.5 ± 3.0, p < 0.001; galactose 61.5 ± 10.7, p < 0.05) compared to that in the control (106.0 ± 17.8). Fetuin also inhibited binding (51.2 ± 16.3, p < 0.02), but sialic acid, fucoidin, ovalbumin, orosomucoid, d-glucose, mannose, d-lactose, and N-acetyl glucosamine did not (p > 0.05). This indicates that the galactose in asialofetuin and fetuin is involved in a specific lectin-like interaction between equine sperm and oviductal epithelium.