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Renin in the blood
Last reviewed: 05.07.2025
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The reference concentration (norm) of renin in blood plasma when blood is collected in a horizontal position (lying down) is 0.2-1.6 ng/(ml.h) of angiotensin I; in a vertical position (standing) - 0.7-3.3 ng/(ml.h) of angiotensin I.
Renin is a proteolytic enzyme secreted by a group of cells located in the immediate vicinity of the renal glomeruli (and therefore called the juxtaglomerular apparatus). Secretion of renin in the kidneys is stimulated by a decrease in blood pressure in the arteries leading to the glomeruli, a decrease in the sodium concentration in the macula densa and distal tubules, and by activation of the sympathetic system. The most important factor increasing the formation of renin is a decrease in renal blood flow. Reduced renal blood flow is often due to a general decrease in arterial pressure. Renin released into the blood acts on angiotensinogen, resulting in the formation of biologically inactive angiotensin I, which is further converted by ACE to angiotensin II. ACE, on the one hand, catalyzes the conversion of angiotensin I into one of the most powerful vasoconstrictors - angiotensin II, on the other hand, hydrolyzes the vasodilator bradykinin to an inactive peptide. In this regard, drugs - ACE inhibitors are effective in lowering blood pressure in patients with renovascular arterial hypertension.
For the evaluation of plasma renin results, only stimulated values (e.g. after stimulation with furosemide) are most significant. When determining the furosemide-stimulated renin level, it is necessary to simultaneously determine sodium and creatinine in daily urine and potassium, sodium and creatinine in the blood. To diagnose arterial hypertension associated with renal artery stenosis or parenchymal damage to one kidney, renin activity is studied in blood taken directly from both renal veins. If the absolute renin activity in the blood from the renal veins is increased or the renin activity from the vein of the affected kidney is more than 1.5 times higher than the renin activity on the healthy side, renal artery stenosis, which impairskidney function, can be confidently stated.
Very high values of renin activity in the blood are observed in reninomas. Renin activity in the blood gradually decreases with age.
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