ABSTRACT
The renin-angiotensin-aldosterone system (RAAS) is one of the oldest hormonal systems-no matter if “old” is defined as phylogenetically old, or if it is defined in the sense of being discovered a long time ago (1). The first description of a RAAS component came from Robert Tigerstedt and his student Per Bergman as early as 1897, when they injected a kidney homogenate derived from a healthy rabbit to another healthy rabbit, resulting in a marked elevation in blood pressure (BP) in the recipient (2). Tigerstedt and Bergman termed the BP rising substance “renin.” It took decades until, in 1934, the groups by Eduardo Braun-Menendez in Buenos Aires and by Irvine Page in Indianapolis coincidentally, but independently, found that the actual BP rising substance was not renin itself, but a molecule that was cleaved and activated by renin, and which is nowadays termed angiotensin II (Ang II) (3,4).
