Mineralcorticoids

The mineralcorticoids are steroid hormones produced by the Zona Glomerulosa. Their name reflects their role in controlling mineral and electrolyte balance in the body.

The primary mineralcorticoid produced by the adrenal cortex is Aldosterone. 

Aldosterone

The structure of Aldosterone: Image courtesy of https://commons.wikimedia.org/wiki/Image:Aldosterone-2D-skeletal.svg Public Domain image

Stimuli for the secretion of Aldosterone include:

·         Dehydration

·         Hemorrage

·         Hyponatremia

·         Hyperkalemia

·         Blood loss

·         --> ultimate hypotension

These are detected by the Renin-angiotensin system, which initiates a biochemical cascade known as the RAA pathway (Renin – Angiotensin – Aldosterone pathway):

1. In response to a decrease in blood pressure, the Juxta Glomerular cells of the kidney secrete Renin into the bloodstream
2. Renin stimulates the liver to secrete Angiotensinogen which is converted into Angiotensin I
3. As blood flows past the lungs, Angiotensin I is converted into Angiotensin II, by Angiotensin Converting Enzyme (ACE)
4. Angiotensin II causes a range of physiological effects including arterial vasoconstriction, and subsequently, Aldosterone secetion from the adrenal cortex
5. Aldosterone stimulates the renal tubules to:

        Increase Sodium reabsorbtion --> less sodium and water in urine

        Increase potassium secretion --> more potassium in urine

6.    Blood volume increases and blood pressure returns to normal.

Drugs acting on this pathway

ACE Inhibitors

These are prescribed in cases of hypertension. They inhibit the ACE enzyme, and as a result reduce water retention, and decrease blood volume and pressure.

Image courtesy of https://upload.wikimedia.org/wikipedia/commons/a/a2/Renin-angiotensin-aldosterone_system.png under the terms of the GNU Free Documentation Liscence. Follow this link for a larger version of the image.