RAT EPIDIDYMIS-SPECIFIC SPERM MATURATION ANTIGENS .1. EVIDENCE THAT THE 26 KD 4E9 ANTIGEN FOUND ON RAT CAUDAL EPIDIDYMAL SPERM TAIL IS DERIVED FROM A PROTEIN SECRETED BY THE EPIDIDYMIS

Monoclonal antibody 4E9, which was raised against a partially purified detergent extract of rat caudal epididymal sperm, recognizes the tail of sperm from the cauda, but not from caput epididymidis, as well as epithelial cells in a restricted region of the distal caput/corpus epi didymidis and proteins in epididymal fluid from corpus and cauda epidi dymidis. The antigen is apparently a glycoprotein, since it is retaine d on a Ricinus communis agglutinin I lectin column. Epididymal fluid a ntigens have apparent M(r)s of 38-26 kD, whereas the membrane-associat ed form of the molecule has an M(r) of 26 kD. Immunocytochemical data and Western immunoblot data suggest that the membrane antigen is deriv ed from the fluid antigen, which, in turn, is secreted by the epididym al epithelium. Characterization of the membrane antigen indicates that it is tightly associated with the sperm surface, behaving as though i t is an integral membrane protein. The antigen persists on ejaculated sperm. (C) 1994 Wiley-Liss, Inc.