OBJECTIVETo investigate the effects of carnitine on human sperm motility and its potential role in the treatment of male infertility diseases.

METHODSWe obtained sperm by testis puncture from obstructive azoospermia patients and cultured them in vitro with normal culture solution (the control group) and the solution with L-carnitine at the concentration of 100 and 250 mmol/L, respectively. We observed the changes in sperm motility and morphology before and after the treatment, detected the expressions of the germ-specific genes, Vasa, Dazl, Acr, Prm1 and ATPase 6.0 by RT-PCR, and investigated the relationship between L-carnitine and the genes associated with sperm development and maturation.

RESULTSAfter 24 -72 hours of treatment, the percentage of motile sperm was significantly higher in the 100 mmol/L L-carnitine group than in the control and 250 mmol/L L-carnitine groups (P < 0.01); the number of forward moving sperm was obviously increased and sperm morphology remained normal in the 100 mmol/L L-carnitine group. RT-PCR showed that L-carnitine increased the expressions of Acr, Prm1, Dazl and ATPase 6. 0 at the concentration of 100 mmol/L, and decreased the expressions of Dazl, Acr and Prm1 at 250 mmol/L.

CONCLUSIONL-carnitine at a proper concentration may improve the motility of incubated testicular sperm by upregulating the expressions of some sperm-specific genes, which helps sperm selection for intracytoplasmic sperm injection. However, a higher concentration of L-carnitine may reduce the expressions of these genes, probably due to its increased toxicity.