Detection of modifications in the tail of capacitated guinea pig sperm using lectins.

The surfaces of uncapacitated, capacitated, and trypsinized guinea pig sperm have been compared using 10 lectins. A previously described assay was used to assess the degree and pattern of agglutination induced by each lectin. Our method of evaluating the agglutination pattern was significantly improved by observing assay plates with an inverted phase contrast microscope at 200 X 320 X magnification rather than with a dissecting microscope. Following in vitro capacitation or trypsinization, the agglutinability of sperm by SBA, DBA, and WGA increased, and the agglutination pattern induced by SBA, DBA, WGA, and RCA120 changed to a predominantly reticular form. These changes did not occur when sperm were incubated in Ham's F-10, a control medium which does not support capacitation. Since binding of these lectins is inhibited by N-acetyl-D-galactosamine (SBA, DBA), D-galactose (SBA, RCA120, DBA), or N-acetyl-D-glucosamine (WGA), we conclude that surface receptors containing these residues are affected by capacitation. By examining assay plates with an inverted phase contrast microscope, we were able to show that the change in the agglutination pattern for all four lectins was due to an increase in agglutinability of the principal piece of the flagellum. It is suggested that the modification of the principal piece detected by this lectin assay may be important in the development of activated motility. Results further show that capacitation and trypsin treatment affect the sperm surface in a similar manner, and are thus consistent with the idea that a trypsin-like enzyme may modify the sperm during capacitation.