中文摘要：

目的：探讨运动性血睾酮降低的胆固醇代谢机制。方法：大鼠在经过5周间歇性负重游泳训练（TA组），造成运动性血睾酮降低的基础上，停训1周（TB组），继续训练1周：维持原负荷（负重5％体重，1组／日，TC组）、负荷量加倍（负重5％体重，2组／日，TD组）、负荷强度增加（负重6％体重，1组／日，TE组），检测大鼠Leydig细胞胆固醇代谢关键环节上的HMG-CoA还原酶、LDL-R、SR-BI及StAR mRNA表达。结果：（1）5周间歇性游泳训练后TA组大鼠血清睾酮显著降低，睾丸Leydig细胞LDL-R mRNA表达量显著升高，SR-BI、HMG-CoA还原酶、StAR mRNA表达量无显著变化。（2）与TA组相比，TB组血清睾酮水平显著升高，LDL-R mRNA表达量显著降低（P〈0．01），SR-BI基因的表达量显著增加（P〈0．01）；TC组血清睾酮有进一步降低的趋势，但无统计学意义，LDL-R mRNA表达量显著降低（P〈0．01），SR-BI、HMG-CoA还原酶、StAR mRNA表达量无显著变化；TD组血清睾酮显著降低（P〈0．05），LDL-R、SR-BI、HMG-CoA还原酶和StAR mRNA表达量显著降低（P〈0．01，P〈0．05）；TE组血清睾酮有进一步降低的趋势，LDL-R、SR—BI、HMG-CoA还原酶mRNA表达量均显著性降低（P〈0．05，P〈0．01），StAR mRNA表达量未见显著变化。结论：（1）Leydig细胞内胆固醇代谢障碍的发生具有阶段性特征；（2）Leydig细胞内胆固醇代谢障碍不是导致运动性血睾酮降低的起始原因，而细胞内HMG-CoA还原酶、LDL-R、SR-BI、StAR基因表达量降低会加速运动引起的血睾酮降低。

英文摘要：

Objective To explore the effects of the one-week swimming with different loads on the gene expressions of HMCr-CoA reductase, LDL-R, SR-BI and StAR in Leydig cells of rats with exercise-induced low serum testosterone. Methods Rats model with low serum testosterone were developed through five-week intermittent swimming training with the load of 5% of body weight （6 days per week, 1 section per day, 6 times of 5-rain swimming per section, with 1-min interval）. In the study, following groups were organized： group Sa （5-week control） ; group Sb （6-week control） ; group TA （rats from the model） ; group TB （rats from the model stopped swimming for 1 week） ; group TC （rats from the model continued same swimming for 1 week） ; group TD （rats from the model continued intermittent swimming with the load of 6% of body weight for 1 week, 1 section per day, 6 times of 5-min swimming per section, with 1-min interval） ; group TE （rats from the model continued intermittent swimming with the load of 5% of body weight for 1 week, 2 sections per day, 6 times of 5-rain swimming per section, with 1-min interval）. Results （1） As compared with the Sa group, remarkable decrease in serum testosterone, and significant increase in mRNA expression of LDL-R were found in group TA. （2） As compared with the group TA, the level of serum T increased significantly, the LDL-R mRNA expression decreased significantly and the mRNA expression of SR-BI increased significantly in group TB, the mRNA expression of LDL-R was decreased significantly in group TC; The serum T decreased significantly and the mRNA expressions of HMCr-CoA reductase, LDL-R, SR-BI, and StAR decreased significantly in group TD; The serum T decreased further and the mRNA expression of HMCr-GoA reductase, LDL-R and SR-BI decreased significantly in group TE. Conclusion （1） There was a staggered characteristics in the＇ cholesterol dysbolism in Leydig＇s cells; （2） Cholesterol dysbolism in Leydig＇s cells was not always the primary re