Renin in the bloodstream hydrolyzes angiotensinogen to yield angiotensin-(1-10) (angiotensin I). Renin is produced in the juxtaglomerular cells of the kidney in response to reduced blood pressure. Aliskiren, a drug used clinically to treat hypertension, inhibits this reaction (Gossas et al. 2011, Wood et al. 2003, reviewed in Gerc et al. 2009).