Objective To explore the effects and mechanism of different duration electroacupuncture(EA)on adaptive hypertrophy of gastrocnemius and the expressions of proliferation cell nuclear antigen(PCNA)

paired box transcription factor 7(Pax 7)

myogenic differentiation antigen(MyoD 1)

myogenin(MyoG)

myosin heavy chain-Ⅰ(Myh 7)

transforming growth factor-β1(TGF-β1)

Smad 3 in rats.Methods Twenty-four SD adult male rats were randomly divided into normal

two-week EA(A 2)

four-week EA(A 4)and eight-week EA(A 8)groups

6 rats in each group.Except the normal group

EA was applied at right"Zusanli"(ST 36)and"Huantiao"(GB 30)for 10 min in the other three groups

separately for 2 weeks

4 weeks and 8 weeks

once a day

6 times a week.The ratio of gastrocnemius wet weight was calculated after EA.The cross-sectional area and diameter of muscle fiber were measured after HE staining.The expression of PCNA protein was detected by immunofluorescence.The relative expressions of Pax 7

MyoD 1

MyoG

Myh 7

TGF-β1 and Smad 3 mRNA were tested with real-time PCR.Results The expressions of PCNA protein were obviously higher in the A 2 and A 4 groups than that in the normal group.The expression of genes in the EA intervention groups showed a trend of increasing first and then decreasing except Smad 3 mRNA.The relative expressions of Pax 7 and TGF-β1 mRNAs reached their peaks in the A 2 group compared with those in the normal group(P<0.01).The ratio of gastrocnemius wet weight

cross-sectional area and diameter of muscle fiber

and the relative expressions of MyoD 1

MyoG

Myh 7 mRNAs reached their peaks in the A 4 group(P<0.01)

while the relative expression of Smad 3 mRNA showed a trend of decreasing first and then increasing and reached its bottom at the 4 th week(P<0.01).Conclusion EA at"Zusanli"(ST 36)and"Huantiao"(GB 30)may induce adaptive hypertrophy of gastrocnemius in rats by up-regulating the expressions of Pax 7

PCNA

TGF-β1

MyoD 1

MyoG

Myh 7 and down-regulating the expression of Smad 3

promoting the proliferation of skeletal satellite cells

myogenic differentiation

myotubes terminal differentiation

increasing the wet weight

fiber crosssectional area and diameter of gastrocnemius.