The origins of the major proteins of boar seminal plasma were identified using starch gel electrophoresis, gel filtration on Sephadex G-200 and surgical removal of various accessory sex glands.
Seminal vesicular secretion accounted for all the major proteins in seminal plasma which migrated to the cathode. Bulbo-urethral proteins could not be detected electrophoretically or by gel filtration. Prostatic-urethral fluid contained at least one protein which migrated to the anode and was not of serum origin. Secretions from the epididymis and/or testis contained at least two proteins which migrated to the anode that were eventually voided in the seminal plasma of the ejaculate.
Boar seminal plasma separated on Sephadex G-200 into three major peaks corresponding to molecular weights of approximately 155,000 (Peak B), 55,000 (Peak A) and 34,000 (Peak C). Peak A proteins were primarily of seminal vesicular origin, while Peak B proteins were primarily of epididymal or testicular origin. Peak C consisted of proteins from all regions of the reproductive tract. Haemagglutinating activity was located between Peaks A and B, associated with molecules of approximately 68,000 molecular weight, and was absent after removal of the seminal vesicles.