Angiotensin I
Sample: Frozen EDTA plasma. See Instructions here
Schedule: Friday every two weeks
Units: ng/mL/hr (Plasma Renin activity, PRA)
Range: 0.2 - 2.8 (In rest) 1.5 - 5.7 (In motion)
Remarks: The biologically inactive Angiotensinogen is converted to the inactive also Angiotyensin I by the enzyme Renin. Renin is a proteolytic enzyme that is produced by the juxtaglomerular cells of the kidney. In the circulation, renin acts to cleave renin substrate to produce the decapeptide, Angiotensin I.
The inactive Angiotensin I then is cleaved by Angiotensin Converting Enzyme (ACE) to form the biologically active octopeptide, Angiotensin II. Angiotensin II is an extremely potent vasopressor that plays an important role in blood pressure regulation. Angiotensin II also stimulates the production of aldosterone by the adrenal gland. Renin activity is used for the differential diagnosis of patients with hypertension: High Renin levels are found patients with hypertension due to renal artery stenosis.
Renin activity also is used in the diagnosis of primary aldosteronism since patients with secondary aldosteronism usually have low Renin levels. In patients with adrenal insufficiency Renin activity is used to assess the adequacy of steroid substitution: Renin activity is normal in patients with adequate supplementation and increased in cases of inadequate steroid substitution.
