Renin-angiotensin system in the kidney: What is new?

The renin-angiotensin system(RAS)has been known for more than a century as a cascade that regulates body fluid balance and blood pressure.AngiotensinⅡ(AngⅡ)has many functions in different tissues;however it is on the kidney that this peptide exerts its main functions.New enzymes,alternative routes for AngⅡformation or even active AngⅡ-derived peptides have now been described acting on AngⅡAT1or AT2receptors,or in receptors which have recently been cloned,such as Mas and AT4.Another interesting observation was that old members of the RAS,such as angiotensin converting enzyme(ACE),renin and prorenin,well known by its enzymatic activity,can also activate intracellular signaling pathways,acting as an outside-in signal transduction molecule or on the renin/(Pro)renin receptor.Moreover,the endocrine RAS,now is also known to have paracrine,autocrine and intracrine action ondifferent tissues,expressing necessary components for local AngⅡformation.This in situ formation,especially in the kidney,increases AngⅡlevels to regulate blood pressure and renal functions.These discoveries,such as the ACE2/Ang-(1-7)/Mas axis and its antangonistic effect rather than classical deleterious AngⅡeffects,improves the development of new drugs for treating hypertension and cardiovascular diseases.