VITRONECTIN IS AN INTRINSIC PROTEIN OF HUMAN SPERMATOZOA RELEASED DURING THE ACROSOME REACTION

Evidence has been presented that oolemmal integrins and their ligands on spermatozoa may play a role in gamete interactions leading to ferti lization. We previously demonstrated that vitronectin (Vn) could be ex tracted from fresh human spermatozoa and detected in Western blots, an d Vn was observed on the surface of living, capacitated sperm by indir ect immunofluorescence. In the present experiments, messenger RNA enco ding Vn was detected in human testis poly (A(+)) RNA using Northern an alysis, and Vn was localized within the acrosomal region of ejaculated sperm by immunoperoxidase and immunofluorescence staining. During the acrosome reaction, induced in capacitated spermatozoa by lonomycin, V n was released into the medium in a calcium-dependent manner. Vn appea rs to be a specific product of intratesticular spermatozoa that is sec reted during the acrosome reaction. These findings suggest that Vn is positioned to play a strategic role in gamete interactions leading to fertilization. (C) 1994 Wiley-Liss, Inc.