IMMUNOLOCALIZATION OF PROACROSIN ACROSIN IN RABBIT SPERM DURING ACROSOME REACTION AND IN SPERMATOZOA RECOVERED FROM THE PERIVITELLINE SPACE/

The participation of acrosin in mammalian sperm penetration through th e zona pellucida has been amply debated. In this paper we report the i mmunolocalization-by silver enhanced immunogold technique using ACRO-8 C10 monoclonal antibody to human acrosin-of proacrosin/acrosin on ejac ulated rabbit spermatozoa incubated in vitro in a capacitating medium and on spermatozoa recovered from the perivitelline space. After incub ation in a capacitating medium, four different patterns were observed: (1) no labeling on acrosome intact spermatozoa; (2) labeling on the r im of the head; (3) labeling on the whole acrosome area; and (4) no la beling on acrosome reacted spermatozoa. At the start of incubation, sp ermatozoa with pattern 1 were the most abundant, whereas at the end of the 32 h incubation period, patterns 2 and 3 were the most frequent. On the other hand, 625 perivitelline spermatozoa were recovered from 1 7 fertilized rabbit eggs, of which 26% were labeled with the antiacros in monoclonal antibody ACRO-8C10 in two different areas: (1) only on t he equatorial region; and (2) only on the postacrosomal area. These re sults are consistent with the idea that proacrosin/acrosin remains ass ociated to the acrosome reacted spermatozoa for long periods of time, and that proacrosin/acrosin associated to perivitelline spermatozoa co uld be responsible for the second penetration of fresh rabbit eggs by perivitelline spermatozoa. (C) 1994 Wiley-Liss, Inc.