Role of direct contact between spermatozoa and oviductal epithelial cells in maintaining rabbit sperm viability.

In many species, including the rabbit, spermatozoa attach to the apical plasma membrane of oviductal epithelial cells. Attachment to oviductal epithelial cells has a beneficial effect on the maintenance of sperm viability during storage in the oviduct, but the mechanism by which this occurs is unknown. The present study was conducted to determine the role of direct contact between spermatozoa and the apical plasma membrane of oviductal cells in maintaining sperm viability. To accomplish this, an apical plasma membrane fraction was isolated from homogenized rabbit oviducts and kidney (control) by differential precipitation. When viewed by electron microscopy, this fraction was composed of closed, roughly spherical apical membrane vesicles (AMV) 50-300 nm in diameter. Analysis of anovulatory, preovulatory, and periovulatory oviductal AMV by one-dimensional PAGE revealed 19 major bands. Densitometry revealed quantitative changes in these bands in relation to reproductive stage. Rabbit spermatozoa were incubated for 48 h in the presence of anovulatory, preovulatory, and periovulatory oviductal AMV. As controls, spermatozoa were incubated with rabbit kidney AMV or in defined medium (DM) alone. There was no significant (p < 0.05) decline in viability for spermatozoa incubated with periovulatory oviductal AMV during the 48-h incubation period. In contrast, viability dropped significantly by 12 h for spermatozoa incubated with preovulatory and anovulatory oviductal AMV, kidney AMV, or DM alone. Periovulatory oviductal AMV were significantly more effective at maintaining sperm viability than preovulatory or anovulatory oviductal AMV. Sperm viability in the presence of kidney AMV was not significantly different from that in DM alone. From these data it can be concluded that direct membrane contact between spermatozoa and oviductal epithelial cells plays a role in maintaining sperm viability. Furthermore, this effect appears to be tissue specific and related to reproductive stage.