MAPK3 and hypertensive disorder: The high salt intake enhanced cardiac expressions of prorenin, renin and (pro)renin receptor as well as the upregulation of cardiac angiotensinogen and angiotensin II AT1 receptor, and activated its downstream signals ERK1/2, TGF-β1, p38MAPK and HSP27, leading to the acceleration of cardiac interstitial fibrosis, perivascular fibrosis and cardiomyocyte hypertrophy at an early stage of hypertension.