Overview of the renin-angiotensin-aldosterone system [8,9]. Angiotensinogen (or renin substrate) is a 56-kD glycoprotein produced and secreted by the liver. Renin is produced by the juxtaglomerular apparatus of the kidney, as shown in Figures 2-8 and 2-9. Renin cleaves the 10 N-terminal amino acids from angiotensinogen. This decapeptide (angiotensin I) is cleaved by angiotensin converting enzyme (ACE). The resulting angiotensin II comprises the 8 N-terminal amino acids of angiotensin I. The primary amino acid structures of angiotensins I and II are shown in single letter codes. Angiotensin II increases systemic vascular resistance (SVR), stimulates aldosterone secretion from the adrenal gland (indicated in gray), and increases sodium (Na) absorption by renal tubules, as shown in Figures 2-15 and 2-17. These effects decrease urinary Na (and chloride excretion; UNaV).

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