Objective To investigate the effect of"Jiaji"(EX-B2)-electroacupuncture(EA)preconditioning on structural changes of myocardium and expression of cytochrome P450(CYP450)enzymes in acute myocardial ischemia-reperfusion injury(MIRI)rats.Methods Sixty male Wistar rats were randomly divided into sham operation

model

EX-B2

Neiguan(PC6)

Yanglingquan(GB34)and Quchi(LI11)groups(n=10 in each group).The MIRI model was established by occlusion of the descending anterior branch of the left coronary artery for 30 min

followed by reperfusion for 30 min.EA preconditioning(2 Hz/100 Hz

1 mA)was respectively applied to EX-B2

PC6

GB34

and LI11 for 30 min

once daily for 7 days.Morphological changes of myocardium were observed by H.E.staining.The ultrastructure of myocardial cells was observed by transmission electron microscope(TEM).The protein expression levels of myocardial CYP450(CYP1 A1

CYP2 B2

CYP2 C11 and CYP4 A2)were detected by Western blot.Results In MIRI rats

myocardial pathological changes as swollen

disorganized arrangement

and partially ruptured myocardial fibers with unclear limit and necrosis and infiltration of lots of inflammatory cells under microscope

and focal myofilament degeneration

dissolution and necrosis with interstitial edema

vague mitochondria with swelling and vacuolation

ruptured and disorganized arrangement of crests under TEM were found in the ischemic area

which was obviously milder in rats of both EX-B2 and PC6 groups.After modeling

the expression of myocardial CYP1 A1 and CYP2 B2 protein were significantly up-regulated in the model group relevant to the sham operation group(P<0.05).In EA preconditioning groups

the expression levels of CYP1 A1 and CYP4 A2 proteins in the EX-B2

PC6 and GB34 groups were obviously down-regulated(P<0.01)

and those of CYP2 B2 and CYP2 C11 proteins in both EX-B2 and PC6 groups were markedly up-regulated relevant to the model group(P<0.01).Compared with the EX-B2 group

the expression levels of CYP1 A1

CYP4 A2 proteins in the LI11 group were significantly up-regulated(P < 0.05)

and CYP2 B2

CYP2 C11 proteins were significantly down-regulated(P<0.05).No significant differences were found between the model and sham operation groups in the expression levels of myocardial CYP2 C11 and CYP4 A2 proteins

between the LI11 and model groups in the expression of CYP1 A1

CYP2 B2

CYP2 C11 and CYP4 A2

between the GB34 and model groups in the expression of CYP2 B2

CYP2 C11(all P>0.05).Conclusion EA preconditioning at EX-B2 and PC6 can suppress MIRI induced up-regulation of myocardial CYP450ω-hydroxylase CYP1 A1 and CYP4 A2 expression and further up-regulate the expression of myocardial epoxygenase CYP2 B2 and CYP2 C11 proteins in acute MIRI rats

thus playing a role in myocardial protection.