Successful cryopreservation for human spermatozoa markedly influences the reproductive outcomes of assisted reproductive technologies. But in spite of its usefulness, cryopreservation significantly decreases sperm quality.
l-carnitine has been found to improve the quality of spermatozoa in selected cases with
male infertility. Here, we examined the efficacy of
l-carnitine in improving sperm motility and vitality and reducing sperm
DNA oxidation during cryopreservation. Semen samples from infertile patients (n = 22) were collected and analysed. Cryopreservation medium supplemented with
l-carnitine was mixed with the semen at a ratio of 1 : 1 (v/v). The final
l-carnitine concentration in each cryovial was 0.5 mg ml(-1) per 5 × 10(6) cell ml(-1) . Controls were cryopreserved without addition of
l-carnitine. After 24 h of cryopreservation, thawed sperm samples were analysed for motility, vitality and
DNA oxidation. Sperm vitality was assessed by the
eosin-
nigrosin test, while sperm
DNA oxidation was measured by flow cytometry. Addition of
l-carnitine significantly improved sperm motility and vitality (P < 0.05) compared with the control. The flow cytometry experiment showed no statistical difference (P > 0.05) in the levels of
DNA oxidation between samples and controls. In conclusion,
l-carnitine improves human sperm motility and vitality, but has no effect on sperm
DNA oxidation after cryopreservation.