Renin–Angiotensin System

Few important points regarding the Renin–Angiotensin System

- Renin is an aspartyl protease, contains 340 AA, t ½ <>

- After Nephrectomy the prorenin levels may actually rise (from ovaries), but rennin falls to 0.

- Angiotensinogen is found in the 2-globulin fraction.

- Angiotensinogen -> AT-I (decapeptide) -> (ACE) AT-II (octapeptide) in Lungs. ACE is a dipeptidyl carboxypeptidase that splits off histidyl - leucine from the physiologically inactive angiotensin I. AT II t ½ 1-2 minutes. The normal PRA in supine subjects eating a normal amount of sodium is approximately 1 ng of angiotensin I generated /mL/hr. The plasma angiotensin II concentration in such subjects is about 25 pg/mL (approximately 25 pmol/L).
- Dry Cough in ACEI is d/t increased Bradykinin.

- AT1 receptors are serpentine receptors coupled by a G protein (Gq).
- 1. JG cells (granular cells) - in the media of the afferent arterioles – intra renal pressure sensor, 2. Agranular lacis cells those are located in the junction between the afferent and efferent arterioles in the mesangium, 3. Macula densa (part of tubule – start of DCT, senses Na+) All 3 constitutes JGA.

- GOLDBLATT Hypertension – Syn. Renal Hypertension – decreased blood supply to one kidney -> increased renin.