Dystrophin Content And Membrane Function Affected By Eccentric Exercise

1 PurposeInvestigate the content changes of dystrophin, a sarcolemma skeleton protein, after eccentric exercise and training. Analyze the relationship between dystrophin deficiency and serum enzyme increase. Evaluate the injury style and the effect on the dystrophin after exercise induced injury.2 Experimental MethodsMale Wistar rats, weighing 300-360g, were performed an acute eccentric exercise and 6 weeks eccentric training. The acute eccentric exercise was -16°incline running on the treadmill at a speed of 26.8m/min, 5min×10groups with 1min rest. 6-wk training involves the 5days/wk, and the speed from 20.0m/min in the first week to 35.0m/min in the last three weeks, and the grade was always -5°. The tissues were collected from the gastrocnemius muscle of the experimental rats.Transverse muscle sections (15μm ) were cut at -20℃. Muscle fiber typing was diagnosed using metachromatic dye-ATPase methods. Dystrophin content was determined by immunohistologically stain and Western blotting methods. The expression of dystrophin gene was detected by in situ hybridization with oligo nucleotide probe, digoxigenin labeled. Images acquired from stained sections were analyzed with Scion Image.CK, LDH in serum, SOD, MDA in muscular tissue, and Na+-K+-ATPase activity in sarcolemma were measured respectively. The muscular cell membrane lipid fluidity and protein mobility were labeled with DPH and N[3P]M respectively and measured by fluorescence spectrophotometer.3 Results3.1 The dystrophin content in fiber I kept steady just after eccentric exercise, decreased slowly after 4h and 24h, and reduced obviously at 48h and 72h (P<0.05). The dystrophin content in fiber IIa was not changed at all period. It decreased in fiber IIb immediately after eccentric exercise (P<0.05), and kept steady at the following periods.3.2 The expression of dystrophin gene reduced to 28% of sedentary level just after eccentric exercise (P<0.05), then increased to 172% of sedentary level at 48h.3.3 The content of dystrophin in muscular tissue tended to increase during 6wk training. And it tended to reduce less after eccentric exercise following the 6wk training than that in sedentary rats raised 6wk.3.4 After eccentric exercise, the membrane lipid fluidity was reduced gradually, and got the lowest level at 48h. On the contrary, the membrane protein mobility was increased gradually after eccentric exercise, and got the highest level at 12h, then down at 24h, up again at 48h. After eccentric exercise following 6wk training, the membrane lipid fluidity was lower than that of sedentary group, and the membrane protein mobility was not changed obviously.3.5 There was no remarkable relationship between sarcolemma skeleton protein content and freedom ion metabolic, serum CK, and serum LDH. On the other hand, dystrophin content negatively related to the membrane protein mobility (r=-0.722, P<0.05). 3.6 There was positive relationship between the serum CK and membrane lipid fluidity (r=0.802) after eccentric exercise following the 6wk training. The sarcolemma Na~+-K~+-ATPase was in relation to membrane lipid fluidity (r=0.518).4 Conclusions4.1 The dystrophin in fiber type IIb reduced during or immediately after the eccentric exercise, and the dystrophin in fiber type I decreased in delayed injure.4.2 The content of dystrophin in sarcolemma tended to increase after eccentric training.4.3 The decrease of skeleton protein made the membrane protein mobility increased, which affected the membrane permeability and the ATPase activity through changing the lipid fluidity.