Carnitine and acetylcarnitine in motile and immotile human spermatozoa.

Human sperm were found to contain acetylcarnitine, carnitine, and only traces of propionylcarnitine and four-carbon acylcarnitines. Carnitine and acetylcarnitine were present in higher concentrations in sperm than in the corresponding seminal fluid samples, and the degree of acylation of carnitine was greater in sperm than in seminal plasma. The ratio of acetylcarnitine/carnitine was 1.77 +/- 0.69 in extracts of sperm from samples with a low degree of motility (0-10% motile), whereas it was 4.70 +/- 1.58 in samples which were 40-80% motile. The possible significance of this difference with regard to the degree of acylation of coenzyme A is discussed.