OBJECTIVEOvertraining is a serious problem in sports, assessed by comprehensive multi-index evaluation, but so far there is still no sensitive, specific monitoring indicator or simple evaluation method to evaluate it. This research established a method for detecting plasma cell free DNA (cfDNA) of rats by real time PCR and discuss edits significance: a new molecular marker of overtraining?

METHODSTwelve male SD rats were randomly divided into control group and overtraining group. The overtraining group rats were undertaken overtraining on a motor-driven treadmill for 5 weeks, while the control group rats kept quiescent. All the rats were drawn blood at pre-and after-5 weeks to detect plasma levels of cfDNA, testosterone (T) and corticosterone (Cort) as well as peroxidation/antioxidation parameters (T-AOC, MDA, SOD, GSH-Px) and creatin kinase (CK).

RESULTS(1) Plasma cfDNA of rat was detected specifically by our real time PCR. (2) Compared with control group rats, the plasma cfDNA of overtraining rats increased obviously (about 5.43 fold). (3) Plasma cfDNA was related to plasma T, Cort, T/C ratio and MDA (correlation coefficent were -0.729, 0.854, -0.655 and 0.720, respectively) rather than plasma T-AOC, GSH-Px, SOD and CK.

CONCLUSION(1) A real time PCR method was established successfully to determine plasma cfDNA of rat. (2) A remarkable raises of plasma levels of cfDNA were found in overtraining rats which were associated with T, Cort and T/C, suggested that plasma cfDNA might be a new molecular marker of overtraining. (3) The increase of plasma cfDNA of overtraining rat might correlate with enhanced oxidative stress induced by overtraining instead of muscle damage.