Angiotensinogen

Angiotensinogen (from human blood serum) [643I5-I6-8]. Purified by chromatography on Blue Sepharose, Phenyl-Sepharose, hydroxylapatite and immobilised 5-hydroxytryptamine [Campbell et al. Biochem J 243 121 1987]. 

Renin Kidney Conversion of angiotensinogen to angiotensin I regulation of blood pressure... 

In the zona glomemlosa of the adrenal gland, renin is locally synthesized, and together with angiotensinogen and ACE generates angiotensin II, which acts as... 

The kidney contains the major site of renin synthesis, the juxtaglomerular cells in the wall of the afferent arteriole. From these cells, renin is secreted not only into the circulation but also into the renal interstitium. Moreover, the enzyme is produced albeit in low amounts by proximal tubular cells. These cells also synthesize angiotensinogen and ACE. The RAS proteins interact in the renal interstitium and in the proximal tubular lumen to synthesize angiotensin II. In the proximal tubule, angiotensin II activates the sodium/hydrogen exchanger (NHE) that increases sodium reabsorption. Aldosterone elicits the same effect in the distal tubule by activating epithelial sodium channels (ENaC) and the sodium-potassium-ATPase. Thereby, it also induces water reabsotption and potassium secretion. 

Rgure42-2. Activity of angiotensinogen in relation to increased blood pressure. (Adapted from Scanlon Sanders [1999]. Essentials of anatomy and physiology [3rd ed., p. 295], Philadelphia FA Davis.)... 

The N-terminal peptide fragment of des-angiotensinogen Val-Ile-His-Asn contains two strongly hydrophobic amino acid residues on the N-terminal site of His-3. The potentiometric data have shown that the NiH.2L complex with this albumin-like sequence is more than two orders of magnitude more stable than the respective complex with Gly-Gly-His.1744 The NMR-based molecular structure has shown that the side chains of Val-1 and lie-2 form a well-ordered hydrophobic fence (Figure 21) shielding one side of the coordination plane from the bulk of... 

This multistep process is initiated by the enzyme renin. Angiotensinogen is a precursor peptide molecule released into the circulation from the liver. 

In the presence of renin, an enzyme produced by specialized cells in the kidney, angiotensinogen is split to form angiotensin I. This prohormone is then acted upon by angiotensin-converting enzyme (ACE) as the blood passes through the lungs to form Ag II. Angiotensin II acts directly on the adrenal cortex to promote aldosterone secretion. 

Angiotensinogen converting ACE-inhibitors (enalapril, Variation of ACE efficacy in the treatment of Susceptibility to essential hyperten-... 

---