Phosphatidylcholine of blood lipoprotein is the precursor of glycerophosphorylcholine found in seminal plasma.
Glycerophosphorylcholine (GPC) concentration of the male reproductive tract increases from under 0.1 mM in the efferent ducts of the testis to 10-50 mM in the cauda epididymidis. It is reasonable to assume that choline-containing phospholipids serve as precursor(s) of GPC but the identity and source of these precursors had not been established. We performed in vivo labeling experiments in rabbits to distinguish between two types of phospholipid metabolism that might account for epididymal GPC formation: (a) addition of phospholipids to sperm during epididymal transit with degradation of these phospholipids by sperm to yield GPC or (b) degradation of phospholipids by epididymal epithelial cells with excretion of GPC into the duct lumen. We concluded that the latter route accounted for most of the GPC accumulation and that the primary source of the choline moiety of GPC was phosphatidylcholine of blood lipoprotein. We believe that these observations established a specific, vectorial metabolism of phospholipids whereby circulating lipoproteins on one side of the epididymal epithelial cell are transferred to the cell, the lipoproteins degraded by the epithelial cell to GPC, and the GPC moved into the lumen.
D000818:Animals; D002250:Carbon Radioisotopes; D002794:Choline / Q000378:metabolism; D005997:Glycerylphosphorylcholine / Q000096:biosynthesis*; D007700:Kinetics; D008297:Male; D010713:Phosphatidylcholines / Q000097:blood*; D011817:Rabbits; D011865:Radioisotope Dilution Technique; D012661:Semen / Q000378:metabolism*; D012741:Sexual Maturation; D013737:Testis / Q000378:metabolism
D002250:Carbon Radioisotopes; D010713:Phosphatidylcholines; D005997:Glycerylphosphorylcholine; D002794:Choline