Abstract: Objective:To investigate the effects of overtraining on the phagocytosis of peritoneal macrophages and the roles of IGF-1 and MGF in this process.Methods:16 male wistar rats were randomized to 2 groups:sedentary group(n=8) and overtraining group(n= 8).Overtraining group was training in standard treadmill with an increasing load for 11 weeks.36 h after the last session of exercise,record the body weight,blood was sampled at the retro-orbital sinus to determine the contents of hemoglobin and testosterone.Rats were sacrificed by decapitation,and then peritoneal macrophages were isolated and purified.The phagocytosis and mRNA levels of IGF-1 and MGF were measured by the uptake of neutral red and real-time PCR respectively.In addition,we evaluate the effects of IGF-1 and MGF peptide on phagocytosis of peritoneal macrophages in vitro(MФs were exposed to different concentrations of IGF-1 or MGF peptide for 2 h).Results:There was a decline of body weight(by 19.3%),hemoglobin(by 13.5%) and testosterone(by 55.3%) in overtraining group when compared with control group(P<0.01).Overtraining significantly inhibited phagocytosis of MФs(declined by 27%,P<0.05).When compared with the control group,IGF-1 and MGF mRNA level in MФs from overtraining group increased 21-fold and 92 fold,respectively(P<0.01).In vitro experiments showed that IGF-1 had no significant effects on phagocytosis of MФs,there were no significant difference in each concentration when compared with untreated cells(P>0.05).Unlike IGF-1,MGF peptide impaired the phagocytosis of MФs in dose-independent manner.There were signifcant differences in 10 ng/ml(P<0.05),50 ng/ml(P<0.05),100 ng/ml(P<0.01),200 ng/ml(P<0.01),when compared with the untreated cells.There were no significant difference between different concentrations of MGF(P>0.05).Conclusion:These results suggest that overtraining inhibits the phagocytosis of peritoneal macrophages,and MGF produced by macrophages may play a key role in this process.