[Intra-spermatic L-carnitine and survival of sperm motility]

The aim of this work was to evaluate the intrasperm carnitine (L-C) content related to sperm motility survival in bovine cervical mucus and in culture medium (Tyrode solution).

The following subjects were selected: 15 fertile normospermic subjects (according to WHO guidelines) and 31 male partners of infertile couples (semen profile: volume > 2.0 ml; concentration > 20 x 10(6)/ml, progressive motility > or = 25% (WHO categories "a" and "b") after fluidification, abnormal forms < 70%; round cells < 1.0 x 10(6)/ml). After standard semen analysis, the samples were subdivided into three aliquots in order to carry out: a) intrasperm L-C (free, total and acetylated) assay; b) sperm motility survival in bovine cervical mucus; c) sperm motility survival in culture medium.

A strict correlation was found between L-C (total and acetylated) content and motility survival in cervical mucus. This is probably due to the fact that in cervical mucus lipids are an important energy source for sperm and to metabolize these lipids intrasperm L-C is essential. Therefore, L-C content can be considered as an indicator of sperm motility life-span in cervical mucus. A significant correlation, even if reduced compared with cervical mucus, was also observed between L-C (total and acetylated) content and sperm motility survival in the biological medium. This probably is because the L-C system modulates the reserves of free CoA, essential to the tricarboxylic acid cycle function.

The intrasperm L-C deficit could be due to; a) alterations in the L-C uptake mechanisms in the epididimys due to inflammatory processes; b) lack of testosterone (L-C uptake is androgen-dependent). Therefore, the therapeutic implication of this finding is that where hypomotility is due to intrasperm L-C deficit, exogenous L-C administration or improvement of L-C epididymal testosterone-dependent uptake could promote the acquisition of sperm motility.