This process may even lead to cell deterioration that was not observed, in fact only live sperm cells were imaged. Moreover, paraformaldehyde-fixed cells showed similar distribution of biotinylated carbohydrate probes (results not shown), which would at least indicate against a lateral movement of the sperm lectins from a distinct surface area of the sperm head toward the apical tip. Nevertheless, at the spatial resolution limit of CLSM, it is not possible to discriminate whether or not our labeling protocol may have caused sperm lectin aggregation within the stained apical tip area of the sperm head.
Bicarbonate is a primary trigger for reduction of carbohydrate staining. Heparin and endogenous GAG (especially in the native proteoglycan state) additionally decreased carbohydrate staining. Although it is unclear how much follicular fluid really enters the oviduct at the time of ovulation, follicular fluid can directly affect the sperm release from the oviductal epithelium even at low concentration. Moreover, the oviduct has been shown to actively secrete GAG that may function in sperm release from the oviduct epithelia.