Human semen contains membranous vesicles called prosta- somes. They are secreted by the prostate gland and contain large amounts of cholesterol, sphingomyelin, and Ca2. Prostasomes enhance the motility of ejaculated spermatozoa and are in- volved in a number of additional biological functions.
No prostasome-like vesicles have been described in horse se- men up to now. We have demonstrated the presence of pros- tasome-like vesicles in the equine semen and characterized them as to size, morphology, and lipid composition; we have found that they are similar to human prostasomes in many re- spects. We propose that these vesicles might be important for the fecundity of horse semen. This is of interest since the success of artificial insemination is limited by the fact that stallion sperm barely survive cryopreservation
