[Metabolism and action of L-carnitine: its possible role in sperm tail function]

The authors report a review on the L-carnitine effects on the male genital tract. L-carnitine represents a cofactor in the transport of long chain fatty acids inside mitochondria and their subsequent oxidation. Therefore, its main role is that of intramitochondrial vehicle of acyl groups. In particular, the effects of L-carnitine on the male genital function seem connected mainly with the high concentration of L-carnitine in the epididymis; the uptake of the L-carnitine from the blood is an active, in part androgen-dependent, mechanism. Moreover, epididymal spermatozoa are able to concentrate L-carnitine (while they become progressively more impermeable to such a substance) during their passage from the caput to the cauda epididymis. The main function of the L-carnitine in the epididymis is to give to the spermatozoa an energetic substrate. In fact, this function should be of great importance since the epididymal spermatozoa employ fatty acid oxidation for their energy metabolism; on the contrary, the ejaculated sperm employ glycolytic process. As a consequence of the above-mentioned effects of L-carnitine the dosage of this substance in the evaluation of the integrity of the processes of maturation of the spermatozoa was proposed. Finally, there is growing interest in the use of L-carnitine as a therapeutic tool in some forms of male infertility.