| Objective: To measure the content of L-carnitine in twenty healthy fertile men and twenty patients with asthenospermia and to research the effect of L-carnitine of different concentrations on human sperm viability, motility rate, motility function, acrosome reaction (AR) and plasma membrane functional integrity in vitro in order to explore the influence of L-carnitine to human sperm and to assess the tratement of L-carnitine on male infertility.Methods: The sperm fluids of twenty healthy fertile men and twenty patients with asthenospermia obtained by masturbation were incubated at 37℃with different concentrations of L-carnitine. Part one, L-carnitine content were measured by the high-performance liquid chromatography in two groups Part two, the spermatozoa solution was incubated with the different concentrations of L-carnitine (4mM, 8mM, 12mM) at 37℃in vitro. Measurements were carried out at 0,30,60,and 120 min in specimens, including sperm motility, sperm viability and motility function, while establishing control group. Part three, the sperm of two groups were carried out the hypo-osmotic swelling (HOS) test at 60-minute of part two, while establishing normal control group. Part four, the two group of spermatozoa solution which were treated by swim-up technique were incubated with the different concentrations of L-carnitine (4mmol/L, 8mmol/L, 12mmol/L) at 37℃in vitro. The FITC-PSA was used to stain the capacitated spermatozoa that have been incubated for 60 min in vitro, while establishing normal control group. Acrosome reaction induced by L-carnitine, integrity of the acrosome marked by a flowcytometer was measured by flow cytometryResults: Part one, The concentration of L-carnitine measured by high performance liquid chromatography in seminal plasma of two group were (205.67土11.04)μmol/L,(112.24士10.27)μmol/L.L-carnitine seminal plasma in two group were (242.04土14.37) mol ,(374.04士15.30) mol, and had significant difference between groups(P<0.01). Part two, when L-carnitine was added to the sperm fluids of healthy fertile men in vitro, live rate of sperm vitality and motion parameters had no obvious change compared with the control group. But at the same conditions, it can significantly slow a downward trend of the rate of live sperm, vitality and VSL, VCL and VAP, exercise parameters. This effect was strengthened with the increasing concentration of L-carnitine, but it was weakened when the concentration of L-carnitine exceeded 1200μmol/L. The suitable concentration of L-carnitine was approximately 400μmol/L. When the sperm fluid of infertile men with asthenospermia were incubated at 37℃(from 30min to 60min) with different concentrations of L-carnitine (from 400μmol/L to 1200μmol/L) in vitro, the sperm motility and the movement parameters, including VCL, VSL and VAP can be increased significantly. Part three, in healthy fertile men group, the percentage of g type sperm and the total tail swelling rate were not significantly different(P>0.05) among control group, 4mmol/L group, 8mmol/L group, and 12mmol/L group. This showed that L-carnitine had no effect on the sperm membrane integrity with the increasing concentration of L-carnitine. But in asthenospermia group, g type sperm and the total tail swelling rate in experiment group were decreased obviously compared with control group. It showed that the integrity of sperm membrane will be improved after dealing with L-carnitine. Part four, after treating with different concentrations of L-carnitine, the fluorescent marker values had no significant difference among these groups in healthy fertile men group, In the group of asthenospermia , the fluorescent marker values in the 12mmol/L group were lower compared with control group, 4mmol/L group, 8mmol/L group and had significantly difference(P﹤0.05). There were no significantly different(P﹥0.05) among control group , 4mmol/L group and 8mmol/L group. This showed that 12mmol/L L-carnitine can preferable promote the progesterone-induced acrosome reaction.Conclusions: In asthenospermia patients, semen L-carnitine content was lower than healthy fertile men. L-carnitine with suitable concentration can improve human sperm viability, motility rate and motility functions. It can not modify normal zoosperm plasma embrane functional integrity. But it can improve plasma embrane functional integrity in the asthenospermia patients. L-carnitine with suitable concentration can promote the progesterone-induced acrosome reaction; enhance the capacity of sperm to conceive. The results also provided us a theoretical basis and theoretical references for the development of artificial fertilization and fertilization technology in vitro.
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