| Angiotensin I appears to have no biological activity and exists solely as a precursor to angiotensin 2. Angiotensin I is formed by the action of renin on angiotensinogen. Renin cleaves the peptide bond between the leucine (Leu) and valine (Val) residues on angiotensinogen, creating the ten-amino acid peptide (des-Asp) angiotensin I. Renin is produced in the kidneys in response to renal sympathetic activity, decreased intrarenal blood pressure at the juxtaglomerular cells, or decreased delivery of Na+ and Cl- to the macula densa. If less Na+ is sensed by the macula densa, renin release by juxtaglomerular cells is increased. |
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