Renin blockers, more commonly known as renin inhibitors, form a category of pharmaceuticals that suppress renin. Also known as angiotensinogenase, renin is an enzyme and a major participant in the renin-angiotensin system (RAS). In this hormone system that monitors the body’s blood pressure and water or fluid balance, renin in particular plays an important role in the body’s extracellular volume, which consists of substances outside the cell. It also plays a role in the narrowing of the arteries, or arterial vasoconstriction.
The RAS is named for the relationship between renin and a peptide named angiotensin. The latter is formed when renin converts angiotensinogen, a globular protein mainly released into blood plasma by the liver, into angiotensin I. This version of the peptide, however, is inactive. It is when the angiotensin I-converting enzyme (ACE) removes two of its terminal residues that angiotensin I is converted to its active form, angiotensin II.
Thus, renin is responsible for the process that produces angiotensin II, which increases blood pressure and creates hypertension, in two ways. The peptide contracts the muscles that surround blood vessels, particularly the arteries, thereby narrowing them and restricting blood flow. Also, its release of the hormone aldosterone to increase the blood’s reabsorption of sodium and water from the kidneys contributes to hypertension as well as increases overall extracellular volume and the possibility of kidney failure.
The link between renin and hypertension was discovered in the late 19th century, when two physiologists noticed the development of high blood pressure in rabbits that they injected with the enzyme. By the late 20th century, two classes of pharmaceuticals had been developed: ACE inhibitors and angiotensin II receptor antagonists, or angiotensin II receptor blockers (ARBs), which concentrate on different sections of the renin-angiotensin process. ACE inhibitors suppress the enzyme that turns angiotensin I to angiotensin II, while ARBs inhibit angiotensin II itself.
Renin blockers are the latest group of drugs developed for the renin-angiotensin process, specifically when renin turns angiotensinogen into angiotensin I. Pharmaceutical companies began developing renin blockers when it was discovered that chronic use of hypertension drugs actually drove up renin production. Thus, renin blockers had to be invented to stop the process at the very beginning.
A prime example of renin blockers is Remikiren, which Switzerland-based global health-care company F. Hoffmann–La Roche Ltd. introduced in 1996. Another example is Aliskiren, which was approved by the United States Food and Drug Administration (FDA) in 2007. It goes by the trade name Tekturna in the U.S. and Rasilez in other countries.