Description

Plasma renin activity (PRA) is a measure of the activity of the renin-angiotensin-aldosterone system (RAAS) in the body. Renin is an enzyme produced by the kidneys, and it plays a crucial role in regulating blood pressure and fluid balance.

When blood pressure drops or blood volume decreases, specialized cells in the kidneys release renin into the bloodstream. Renin then acts on a protein called angiotensinogen, which is produced by the liver, converting it into angiotensin I. Angiotensin I is then converted to angiotensin II by the angiotensin-converting enzyme (ACE) primarily found in the lungs.

Angiotensin II is a potent vasoconstrictor, meaning it causes blood vessels to narrow, leading to an increase in blood pressure. It also stimulates the secretion of aldosterone from the adrenal glands, which promotes sodium and water retention by the kidneys, further increasing blood volume and pressure.

PRA is typically measured by analyzing the level of angiotensin I in the blood. Higher levels of renin activity indicate increased activation of the renin-angiotensin-aldosterone system, which may be seen in conditions such as dehydration, low blood pressure, kidney disease, or certain hormonal imbalances. Conversely, lower levels of renin activity may indicate suppression of the RAAS, which can occur in conditions such as high blood pressure, heart failure, or excessive sodium intake.

Measuring PRA can help healthcare providers diagnose and monitor various conditions related to blood pressure regulation and fluid balance. It is often performed as part of the evaluation of hypertension (high blood pressure) and other cardiovascular conditions.