Motility Related to the Presence of Carnitine/Acetyl‐Carnitine in Human Spermatozoa

Total carnitine, acetylcarnitine and carnitine acetyl transferase (E.C. 2.3.1.7) were measured in the plasma and spermatozoa fractions of 41 samples of human semen and the correlation with sperm motility and sperm density examined. It was confirmed that the concentration of total carnitine as well as of acetylcarnitine was 2–25 times higher and the activity of carnitine acetyl transferase 20–15 fold higher in spermatozoa than in seminal plasma. Sperm motility correlated with the concentration of acetylcarnitine (r = 0.6, P < 0.01) and of total carnitine (r = 0.55, P < 0.01) but not with the concentration of free carnitine nor with the activity of carnitine acetyl transferase in the spermatozoa. No correlation was found between sperm motility and the concentrations of acetylcarnitine, free carnitine or total carnitine in the seminal plasma. It is concluded that the amount of carnitine present in the spermatozoa probably provides a better index of epididymal function than the carnitine in the seminal plasma as the latter in influenced by af variable contribution from the other accessory sex organs.