Objective: To observe the protection of andrographolide (AP) on rat's myocardial hypertrophy induced by isopropylarterenol (Iso)

explore balance of vasoactive substance. Method: The rat's myocardial hypertrophy model is formed through hypodermic injection which extended 10 days at back skin with Iso

1 mg·kg-1·d-1. Once the model is formed

it will be administrated with various doses of AP

dimethyl sulfoxide(DMSO) or normal saline through hypodermic injection from the second day

and the process will extend 14 days. After the last administration

the rat will be in absolute diet status for 12 h and its blood and heart are taken under anesthesia. The activity of lactate dehydrogenase (LDH) in serum and myocardium tissue

the level of NO in serum

and the content of angiotensin Ⅱ(AngⅡ)

endothelin(ET) and atrial natriuretic peptide (ANP)in plasma were investigated. Result: Compared with control group

Iso group showed a change about activity of LDH which was increased in serum but decreased in myocardium tissue

a descended level of NO in serum

improved content of AngⅡ and ET while reduced content of ANP in plasma. However

the activity of LDH is depressed in serum and elevated in myocardium tissue in AP groups

furthermore

the level of NO and ANP were enhanced while the content of AngⅡ and ET were reduced in AP groups. Conclusion: AP has a protection on rat's myocardial hypertrophy caused by Iso

and its mechanism probably result of modulating the homeostasis of AngⅡ

ANP

ET and NO.