Renin, plasma renin activity (ARO) – examination and interpretation of results

Renin is a proteolytic enzyme produced by the secretory cells of the supply vessel of the glomerulus. It acts on the hepatic protein angiotensinogen, cleaving angiotensin from it. The final stage of system stimulation is the release of aldosterone, which reduces the excretion of sodium ions into the urine at the expense of increasing the excretion of potassium ions.

Plasma renin activity (ARO) – characteristics

Renin is an enzyme produced by the secretory cells of the supply vessel to the glomerulus. It is responsible for the conversion of angiotensinogen to angiotensin I, which transforms into angiotensin II (which stimulates the secretion of aldosterone). The purpose of the ARO test is to determine the degree of activity of renin. It allows to determine what amount of angiotensin I was produced from 1 ml of blood within one hour of incubation under laboratory conditions. The test is intended, among others, for people with electrolyte disturbances and suspected renin-producing cancer.

The result of the plasma renin activity test depends on the body position of the subject and the salt content in his diet.

Indications for the ARO examination

The most common indications for plasma renin activity include:

1. Suspicion of secondary arterial hypertension in the course of hyperaldosteronism.

2. Suspicion of the presence of a renin-producing tumor.

3. Electrolyte disturbances.

Often, along with the ARO test, blood aldosterone levels are measured.

Plasma renin activity – study

Before you decide to test plasma renin activity:

  1. two weeks before the test, avoid drugs that affect ARO (including beta-blockers, angiotensin converting enzyme inhibitors, renin inhibitors),
  2. take care to compensate for any potassium deficiencies,
  3. four weeks before testing, stop taking diuretics.

Important! All actions should be taken under the supervision of a physician. Do not stop taking medications yourself without consulting a specialist!

Material for the ARO test: plasma.

Preparation for testing plasma renin activity: the test is performed twice: 1) after the administration of a normal-salt diet providing 100-120 mmol of sodium ions per day and after spending the night before taking blood in the supine position (resting ARO), 2) after a three-day diet with sodium restriction to 20 mmol / day and 3-4 hours of standing upright (postionization ARO).

The course of the study: sampling blood from a vein in the arm several times.

Time to wait for the result: 1 Day.

Reference values ​​may differ depending on the laboratory where the test was performed.

Standard:

– ARO at rest: 0,32 ± 0,05 pmol / l / h (1,46 ± 0,23 ng / ml / h),

– Post-ionization ARO: 1,29 ± 0,19 pmol / l / h (6,5 ± 0,87 ng / ml / h).

Comments: The renin-angiotensin-aldosterone system is involved in the regulation of the water-electrolyte and acid-base balance and the proper filling of the vascular bed. Filling the vascular bed is one of the main determinants of blood pressure. The test result may be falsified by the use of non-steroidal anti-inflammatory drugs.

Plasma renin activity – interpretation

High plasma renin activity is observed in the case of:

  1. pregnancy,
  2. pheochromocytoma,
  3. taking oral hormonal contraceptive pills,
  4. kidney ischemia,
  5. hypovolemia,
  6. treatment with preparations such as angiotensin II receptor blocking sartans and angiotensin converting enzyme inhibitors,
  7. Bartter’s syndrome (this disease is characterized by hyperaldosteronism),
  8. cirrhosis of the liver,
  9. renovascular hypertension or malignant hypertension.

In turn, the decrease in ARO is characteristic of:

  1. a diet high in sodium
  2. people using beta-adrenergic blockers,
  3. primary hyperaldosteronism,
  4. disturbed secretion of renin,
  5. diseases that lead to damage to the glomerular apparatus.

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