Concentrations of sperm, protein and a sperm membrane glycoprotein within boar epididymal luminal fluids.

Boar rete testis fluid and luminal contents from nine epididymal segments were collected for analysis. From proximal to distal, segments were designated A, B, C (caput), Da, Db, Ea (corpus) and Eb, Fa, Fb (cauda). Concentrations of sperm, protein and soluble sperm membrane glycoprotein S2P3 were lowest in the caput epididymidis (region A) and highest in the proximal corpus epididymidis (region Da). At region Da, approximately 94% of the fluid that had entered the epididymis had been reabsorbed. More total protein was found in the luminal fluid of region Da than could be accounted for on the basis of concentration via fluid removal. The proximal cauda epididymidis was the major luminal protein-removing region. However, large amounts of glycoprotein S2P3 were removed from the luminal fluids during passage through the caput epididymidis, and smaller amounts were removed during passage through the cauda epididymidis.