The Importance of Seminal Plasma for Human Sperm Motility

Epididymal spermatozoa suspended in a buffered salt solution are characterized by flagellating tail motion with no or very poor progressive motility. Addition of seminal plasma to a final concentration of 8% (v/v) or albumin to 4% (w/v) immediately initiates progressive motility. Human spermatozoa with good progressive motility in the whole ejaculate, after having been washed three times with an albumin-free buffered salt solution, show a motility pattern similar to that of epididymal spermatozoa. Addition of seminal plasma or human albumin (8 and 4%, respectively) immediately restored the good progressive motility. The effects of “prostatic” and “vesicular” fluids on the motility pattern of washed ejaculated spermatozoa were studied by adding fluid from the various fractions of split ejaculates (S.E.) to 1 ml suspensions of spermatozoa. At low concentrations, (2–4%) fluid from the middle fractions of S.E. had the greatest effect on the progressive motility. At higher concentrations (6–8%), fluid from the first fraction was most effective. Fluid from the last fractions usually had a very weak positive effect at a low concentration (2%) but a depressive effect at higher concentrations (6–8%). Epididymal spermatozoa had a susceptibility to and affinity for eosin that was characteristically different from that shown by ejaculated spermatozoa. There was no difference in this respect between epididymal and ejaculated spermatozoa washed three times in an albumin-free buffered solution.