Seasonal variation of goat seminal plasma proteins.

The present study describes the investigation of seasonal changes in seminal plasma proteins of Saanen goats under natural conditions in south Brazil. Proteins were isolated by liquid chromatography on heparin Sepharose CL-6B column and characterized by polyacrylamide gel electrophoresis (PAGE). Important differences were observed in the pattern of heparin-affinity proteins (HAPs), such as a band of 178 kDa unique to the breeding season; a decrease in 119 kDa proteins; and an increase in proteins ranging from 73 to 104 kDa. HAP caused deterioration of sperm motility and acrosome breakage in media containing and not containing skimmed milk; the effect was most remarkable with the proteins from the nonbreeding season. Furthermore, HAP presented phospholipase A2 (PLA2) activity, which was 4.4-fold higher in nonbreeding season than in breeding season. Binding sites for HAP were identified in the sperm surface, particularly at the middle piece of the spermatozoa. These results indicate that proteins from goat seminal plasma are under seasonal control and associated with sperm function during breeding and nonbreeding seasons.