renin

see also:

• angiotensin
• aldosterone
• ACE inhibitors

image courtesy of wikipedia

• renin is a peptide which converts circulating inactive angiotensinogen (a globulin produced by the liver) to inactive angiotensin I which is then converted to active angiotensin II by ACE.
• angiotensin II is a peptide hormone that produces vasoconstriction, promotes water and salt retention, increased BP, and stimulates release of aldosterone
• renin was discovered and named in 1898 by Robert Tigerstedt

• renin is secreted by the granular cells of the juxtaglomerular apparatus in afferent arterioles of the kidney in response to three stimuli:
  • baroreceptor response to low BP
  • macula densa detecting decreased sodium in the ultrafiltrate of the nephron
  • beta 1 adrenergic receptor stimulation (see sympathomimetics)