The concentrations of free L-carnitine and L-O-acetylcarnitine in spermatozoa and seminal plasma of normal, fresh, and frozen human semen.

Free-L-carnitine and L-O-acetylcarnitine concentrations have been determined in spermatozoa and seminal plasma of normal, fresh, and frozen human semen. Results show that in fresh semen most of the free L-carnitine (0.213 +/- 0.02 mM) and L-O-acetylcarnitine (0.063 +/- 0.007 mM) is found in the seminal plasma. In contrast to other worker's results, the concentrations of free L-carnitine and L-O-acetylcarnitine in spermatozoa were found to be high and were 0.384 +/- 0.066 mumole/10(9) spermatozoa (22 mM) and 0.376 +/- 0.057 mumole/10(9) spermatozoa (21.6 mM), respectively. It is also demonstrated that the distribution of soluble metabolites such as L-carnitine between spermatozoa and seminal plasma is altered by the freezing of semen. After freezing and storage of semen at -20 degrees C for 7 days, the intracellular concentrations of free L-carnitine and L-O-acetylcarnitine decreased to below the limits of assay.