AIM AND METHODSThe distribution of ErbB2 in mouse testis, epididymidis, ovaries, oocyte-cumulus cells-complexes in oviducts and sperms was investigated immunohistochemically. To study the effect of c-erbB2 on mouse fertilization in vitro, various concentrations of c-erbB2 antisense oligonucleotides (c-erbB2 ASODNs) were incubated with sperms and oocyte-cumulus cells-complexes during fertilization in vitro. To explore possible mechanisms involved in fertilization, the relationship between c-erbB2 ASODNs and GABA, or dbcAMP, or verapamil during fertilization in vitro was also observed.

RESULTSErbB2 oncoprotein was observed in epithelial cells in epididymis, sperms and cumulus cells. C-erbB2 ASODNs inhibited the rate of fertilization in vitro in a dose-dependent way. The fertilization rate of the control group, low (5 micromol/L), medium (10 micromol/L), high (20 micromol/L) concentration c-erbB2 ASODNs group, and nonsense at oligonucleotides group (20 micromol/L) was 38.3%, 19.6%, 10.7%, 5.0%, and 33.8% respectively. Integral optical density immunostaining of ErbB2 in sperms was notably reduced. Medium and high concentration of c-erbB2 ASODNs notably inhibited cumulus cells adhering to inner wall of Petri dish. Treated alone with GABA or dbcAMP, the rate of fertilization was increased. Both GABA and dbcAMP partially inversed the ASODNs inhibition effect on fertilization rate, but neither of them showed significant effect on sperm integral optical density of ErbB2 immunostaining. In contrast, verapamil inhibited fertilization rate. Co-treated with c-erbB2 ASODN, verapamil showed synergic inhibiting effect on fertilization with c-erbB2 ASODN. Verapamil also inhibited the expression of c-erbB2 in sperms.

CONCLUSIONIt is suggested that c-erbB2 is closely correlated with fertilization. Ca2+ may inhibit fertilization in vitro through regulation the expression of c-erbB2 gene in sperm cells, while both of GABA and dbcAMP may affect the process of fertilization through the way other than c-erbB2 expression in sperm cells.