Renin maintains blood pressure through vasoconstriction when there is inadequate salt to maintain volume. In populations where blood pressure is more often high than low, and vascular death more common than haemorrhage or dehydration, therapeutic reductions in renin secretion or response are valuable. Whether long-term benefits are due entirely to blood pressure reduction remains unproved. The pathway can be blocked at its rate-limiting step (β blockade or direct renin inhibition), the synthesis of the active product, angiotensin II, or at the receptor for angiotensin. Because renin and sodium are the two main factors in blood pressure control, and renin levels vary inversely with sodium load, blood pressure control requires a combination of natriuresis and blocking the consequential increase in renin activity. Being a large and stable molecule, renin is among the easiest and cheapest of hormone measurements. Understanding the simple biochemistry and physiology of renin permits optimal use of the drugs acting to raise or suppress this hormone.
- ACEi, ACE inhibitor
- Ang I (II), angiotensin I (II)
- ARBs, angiotensin receptor blockers
- BP, blood pressure
- CCBs, calcium channel blockers
- DRI, direct renin inhibitor
- JGA, juxtaglomerular apparatus
- PRA, plasma renin activity
- RAS, renin–angiotensin–aldosterone system
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↵i Jean-Louis Marie Poiseuille (1799–1869): Laminar flow down a rigid tube is proportional to the pressure difference between the ends. Better known to cardiologists for his subsequent recognition that the proportionality constant includes the tube’s radius raised to the fourth power: R = πr4p/8ηl
Funding: The British Heart Foundation provided programme grant support to the author but were not involved in the writing of the review or the decision to submit the manuscript for publication.
Competing interests: MJB has been reimbursed by Pfizer, Menarini, Novartis, BMS/Sanofi, MSD, Servier and Bayer for speaking engagements or consulting, or both. The Clinical Pharmacology Unit has received research funds from Menarini, Bayer, Servier and BMS/Sanofi.