The renin-angiotensin system (RAS) is one of the most important endocrine (tissue-to-tissue), paracrine (cell-to-cell) and intracrine (intracellular/nuclear) humoral systems in the regulation of blood pressure, cardiovascular, and kidney function in health and disease. The RAS has remarkably evolved from the initial discovery of the rate-limiting enzyme renin to a complex biochemical and physiological cascade involving more than a dozen members. Currently, there are up to five axes or pathways identified in the RAS; each has its substrate, enzyme, effector peptide, receptor, and downstream...