Osteopontin localization in the Holstein bull reproductive tract

Previously we reported that the 55-kDa fertility-associated protein in Hols tein bull seminal plasma (SP) is osteopontin (OPN). The objective of the pr esent study was to localize OPN in tissues and fluids in the Holstein hull reproductive tract to determine its origin. Antisera generated against huma n recombinant OPN, as well as antiserum prepared against purified bovine se minal plasma OPN, reacted with protein in SP, accessory sex gland fluid, se minal vesicle fluid, ampullary fluid, and urine using one- and two-dimensio nal SDS-PACE Western blot analysis. However, these antisera failed to detec t OPN in cauda epididymal fluid or solubilized sperm membranes. Immunofluor escence histochemistry localized OPN in the lumen and epithelial cells of t he seminal vesicle and ampulla, but not in tissues of testis, epididymis, p rostate, and bulbourethral gland. OPN was not detected immunohistochemicall y in epididymal, ampullary, or ejaculated sperm treated with or without Tri ton X-100. We concluded that the primary sources of OPN in bull SP are the seminal vesicles and ampulla.