title: Potential involvement of C(3) complement factor in amphibian fertilization.
abstract: We have assessed the potential involvement of C(3), the third complement factor, and its receptor in Bufo arenarum fertilization. We show that a polyclonal antibody against a B. arenarum C(3)-like factor (C(3)Ba) reacts specifically with components of the extracellular matrix (ECM) of coelomic eggs and the cell membrane of uterine eggs. Interestingly, we have identified a 163 kD protein immunoreactive with a monoclonal antibody against the CD11b alpha chain of the human C(3) receptor on the cell membrane of the animal pole of uterine eggs, the site of entry of the sperm, but not in coelomic eggs (CR3Ba). Treatment of coelomic eggs with a pars recta oviductal-like protease, trypsin, induced the translocation of C(3)Ba from the ECM to the cell membrane. Furthermore, inhibition of CR3Ba by trypan blue, as well as inhibition of C(3)Ba by anti-C(3)Ba on uterine eggs impaired fertilization, whereas identical treatment on sperm cells did not alter percentage fertilization. Our results suggest, (A) that changes in the localization of C(3)Ba from the ECM to the cell membrane may be triggered by trypsin-like proteases during passage of eggs through the oviduct; and (B) that C(3)Ba/CR3Ba may be involved in B. arenarum fertilization.
authors.affiliation: Department of Developmental Biology, National University of Tucuman-CONICET, Chacabuco 461, 4000, S.M. de Tucuman, Argentina.
authors.forename: R J
authors.initials: RJ
authors.lastname: Llanos
authors.forename: C M
authors.initials: CM
authors.lastname: Whitacre
authors.forename: D C
authors.initials: DC
authors.lastname: Miceli
mesh_terms: D000818:Animals; D000906:Antibodies / Q000378:metabolism / Q000494:pharmacology; D000918:Antibody Specificity; D002022:Bufo arenarum / Q000502:physiology*; D003176:Complement C3 / Q000037:antagonists & inhibitors / Q000502:physiology*; D005260:Female; D005306:Fertilization; D005307:Fertilization in Vitro; D005455:Fluorescent Antibody Technique; D008297:Male; D010063:Ovum / Q000378:metabolism; D011951:Receptors, Complement / Q000378:metabolism; D013094:Spermatozoa / Q000378:metabolism
chemical_list: D000906:Antibodies; D003176:Complement C3; D011951:Receptors, Complement