[Effect of exogenous erythropoietin on denervated muscle atrophy]

To investigate the effect of exogenous erythropoietin (EPO) on the denervated muscle atrophy.

Twenty-four SD male rats, weighting 200-220 g were made the models of denervated gastrocnemius muscle after sciatic nerves were transected under the piriform muscle at the right lower leg, and were randomly divided into two groups (n=12). rhEPO (2500 U/kg) was injected daily into the denervated gastrocnemius muscle in EPO group, and normal saline was injected into the denervated gastrocnemius muscle in control group. To observe the general state of health of the experimental animal, the muscle wet weight, the muscle cell diameter, the cross section area, the protein amount, the percentage of the apoptotic muscle cells, and the Na+-K -ATPase and Ca2+ -ATPase activities were measured 2 and 4 weeks after operation.

All experimental animals were survived during experiment without cut infection, and all animals could walk with pulling the right knee. At 4 weeks after operation, 7 cases showed ulcer in the right heel, including 5 in the control group and 2 in the EPO group. At 2 and 4 weeks after operation, the muscle wet weight in EPO group was (885.59 +/- 112.35) and (697.62 +/- 94.74) g, respectively; in control group, it was (760.63 +/- 109.05) and (458.71 +/- 58.76) g, respectively; indicating significant differences between two groups (P < 0.01). The protein amount in EPO group was (77.37 +/- 5.24) and (66.37 +/- 4.87) mg/mL, respectively; in control group, it was (65.39 +/- 4.97) and (54.62 +/- 6.32) mg/mL: indicating significant differences between two groups (P < 0.01). At 2 and 4 weeks after operation, the myofibrillar shapes were nearly normal in EPO group while there were muscle fiber atrophy, some collapse and obviously hyperelastosis between muscle bundle. There were significant differences in the muscle cell diameter and the cross section between two groups (P < 0.01). However, the percentage of the apoptotic muscle cells was 11.80% +/- 1.74% and 28.47% +/- 1.81% in control group, respectively, which was significantly smaller than that in EPO group (21.48% +/- 2.21% and 55.89% +/- 2.88%, P < 0.01). At 2 and 4 weeks after operation, Na+-K+ -ATPase and Ca2+ -ATPase activities in EPO group were higher than those in control group (P < 0.01).

EPO can delay the denervated muscle atrophy.