Regulation of Aldosterone Secretion 

First, think of this system as an important one to maintain blood pressure and blood volume within a normal range.   It is designed to conserve salt and water at the level of the kidney, maintain vascular tone, and will waste  potassium in the urine.

In a straightforward manner, too much activity of the system leads to edema or swelling in the legs, high blood pressure and a low blood potassium level.   Too little activity leads to volume depletion, a low blood pressure, and a high potassium level.   It’s pretty simple.  Right?!

A protein hormone called renin is secreted from the juxtaglomerular apparatus in the kidney.   It is converted from pro renin by the autonomic branch of the sympathetic nervous system.

Renin converts angiotensinogen made by the liver to angiotensin-1.

In the lungs, angiotensin- converting enzyme or ACE, converts angiotensin-1 to angiotensin-2.

Angiotensin-2 stimulates aldosterone production and release by the zona glomerulosa of the adrenal glands.   High potassium levels also stimulate aldosterone release.

Aldosterone acts on the mineralocorticoid receptor in the kidneys to cause resorption of sodium and wastage of potassium.   Water follows the sodium and is also resorbed.  This increases the blood volume.

The macula densa in the distal convoluted tubule of the kidney, located near the juxtaglomerular apparatus,  senses urine flow and along with blood flow sensing by the juxtaglomerular apparatus, regulates renin secretion.

Basically, if you’re volume depleted or have a low blood pressure this system senses the low flow of urine in the kidney, the low blood pressure in the kidney, the low blood pressure in the carotid sinus and activates the sympathetic nervous system and other factors in this cascade to cause salt and water resorption from the urine and vasoconstriction to restore blood pressure and volume.   If all is well the system works behind the scenes to maintain normality.   If one were to ingest too much salt and  water the system would shut down to get rid of the excess salt and water.

There are a lot of medications that intentionally affect this system.  Other medications have unintentional side-effects on this system.  These will be discussed in separate articles.  Also, a number of illnesses can affect the renin-angiotensin-aldosterone system.

The basic measures of the activity of this system include:

• Check for edema
• Check blood pressure and pulse when laying down then after standing
• Check basic metabolic profile including sodium, potassium, BUN and creatinine
• Check plasma renin and aldosterone in the morning and sometimes also in the late afternoon after a patient has been up and about.
• Review medical history and medication list and interpret all data in the proper clinical context.