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 apica l plasma membrane of oviductal epithelial cells. Attachment to oviduct al epithelial cells has a beneficial effect on the maintenance of sper m viability during storage in the oviduct, but the mechanism by which this occurs is unknown. The present study was conducted to determine t he role of direct contact between spermatozoa and the apical plasma me mbrane of oviductal cells in maintaining sperm viability. To accomplis h this, an apical plasma membrane fraction was isolated from homogeniz ed rabbit oviducts and kidney (control) by differential precipitation. When viewed by electron microscopy, this fraction was composed of clo sed, roughly spherical apical membrane vesicles (AMV) 50-300 nm in dia meter. Analysis of anovulatory, preovulatory, and periovulatory oviduc tal AMV by one-dimensional PAGE revealed 19 major bands. Densitometry revealed quantitative changes in these bands in relation to reproducti ve stage. Rabbit spermatozoa were incubated for 48 h in the presence o f anovulatory, preovulatory, and periovulatory oviductal AMV. As contr ols, spermatozoa were incubated with rabbit kidney AMV or in defined m edium (DM) alone. There was no significant (p < 0.05) decline in viabi lity for spermatozoa incubated with periovulatory oviductal AMV during the 48-h incubation period. In contrast, viability dropped significan tly by 12 h for spermatozoa incubated with preovulatory and anovulator y 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 pres ence of kidney AMV was not significantly different from that in DM alo ne. From these data it can be concluded that direct membrane contact b etween spermatozoa and oviductal epithelial cells plays a role in main taining sperm viability. Furthermore, this effect appears to be tissue specific and related to reproductive stage.