[Comparative study of the lipid composition of seminal fluid and ovulatory peritoneal fluid in humans]

Sperm capacitation is accompanied by changes in the lipid composition of the sperm membrane. The purpose of this study is to compare the lipid composition of the semen with that of peritoneal fluid. These two media have opposite effects on sperm capacitation. Cholesterol, triglyceride and phospholipids were measured in seminal fluid (15 specimens) obtained by sperm centrifugation immediately after liquefaction and in the peritoneal fluid at ovulation (15 specimens) obtained through transvaginal puncture. The lipid composition of these two media is different from that of serum. Seminal fluid is characterized by a high level of phospholipids, 14.79 +/- 3.67 g/l as against 0.53 +/- 0.12 g/l in peritoneal fluid. The level of cholesterol is identical in the two media. The cholesterol/phospholipid ratio is therefore lower in seminal fluid than in peritoneal fluid (0.022/0.79). Lecithins are raised in peritoneal fluid as are sphingomyelins and the phosphatidylethanolamines, which are the most important phospholipids in seminal fluid. It therefore can be postulated that the cholesterol/phospholipid ratio, which is low in seminal fluid, and its richness in sphingomyelin brings about stabilization of the membrane cover which corresponds to a decapacitated state, whereas the cholesterol/phospholipid ratio, which is higher in peritoneal fluid, makes for greater fluidity, and this corresponds to the state of capacitation. These preliminary results obtained from human material do not in any way contradict those obtained from animal studies.