OBJECTIVETo identify differential proteins in the seminal plasma of healthy fertile men and non-obstructive azoospermia patients by the shotgun proteomic strategy.

METHODSSix seminal plasma samples from 3 healthy fertile and 3 non-obstructive azoospermia volunteers were collected by Percoll isolation, balanced-mixed, and followed by separation of the mixture by SDS-PAGE. The proteins were subjected to in-gel enzymolysis and isolation of peptide fragments, and then identified by the shotgun proteomic strategy. Then comparative analyses were made between the two groups on the identified proteins with the unique peptide count > or = 2 and = 1 but with the peptide count > or = 4.

RESULTSA total of 213 differential proteins were identified, 133 in the non-obstructive azoospermia patients and 80 in the healthy fertile men. According to the molecular function, these differential proteins mainly fell into the types of signal transduction, cytoskeleton and catalytic activity, especially oxidoreductase activity in the latter type. Eighteen of the differential proteins were found to be of particular significance, including dynein heavy chain, fatty acid synthase, and tubulin alpha-6 chain.

CONCLUSIONThe differential proteins identified in this study were many in number and various in function, which not only demonstrated the value of the shotgun proteomic strategy in protein identification, but also suggested the complicated pathogenesis and varied types of non-obstructive azoospermia. The samples must be selected strictly based on their gene and histological types. Non-obstructive azoospermia was shown to be related with the M phase of the mitotic cell cycle at the protein level, but its specific mechanism remains unknown.