Association of sperm receptor activity with a purified pig zona antigen (PPZA)

Three types of data are presented which suggest that sperm receptor activity is associated with a 58,000 Mr acidic glycoprotein (PPZA) isolated from pig zonae: (1) boar sperm fail to bind to pig zonae pretreated with univalent antibody to PPZA; (2) boar sperm pretreated with PPZA are inhibited in binding to intact pig zonae; (3) binding studies utilizing boar sperm and radiolabeled PPZA indicate an inhibition of radiolabeled PPZA binding to sperm by non-labeled PPZA in a dose-related manner. Collectively these data suggest that, at least in the pig system, the contraceptive action of zona antibodies is accomplished by a specific immunologic reaction between antibody and the zona sperm receptor site rather than to a non-specific blockage of this receptor.