REN and Hypertension: Gao et al. (52, 53) found that green tea had an antihypertensive effect on hypertension induced by a high salt diet in aged male rats, and its main mechanism of action included inhibiting the activity of the renin-angiotensin II-aldosterone system, altering the expression of sodium-potassium pumps in heart, kidney and aortic tissues and increasing the synthesis of nitric oxide in endothelial cells.