MAPK3 and myocardial infarction: This study preliminarily confirmed that PO can reduce myocardial pathological injury; decrease the levels of IL-6, BNP and TNF-α in serum; increase the activities of NOS and cNOS and the level of NO and decrease the levels of iNOS, caspase3, caspase9 and bax by activating the ERK1/2 signaling pathway in MI mice.