Aldosterone's primary function is to regulate the salt and water balance in the body. It achieves this mainly by controlling sodium and potassium levels in the kidneys.
How Aldosterone Works
Aldosterone is a steroid hormone produced by the adrenal glands. It acts primarily on the kidneys, specifically on the distal tubules and collecting ducts, to:
-
Increase Sodium Reabsorption: Aldosterone promotes the reabsorption of sodium ions (Na+) from the urine back into the bloodstream. This increased sodium reabsorption also leads to increased water reabsorption, as water follows sodium.
-
Increase Potassium Excretion: Simultaneously, aldosterone stimulates the secretion of potassium ions (K+) from the blood into the urine, leading to increased potassium excretion.
The Impact on Blood Pressure and Volume
By increasing sodium and water retention, aldosterone contributes to:
- Increased Blood Volume: More water in the bloodstream means a higher blood volume.
- Increased Blood Pressure: The increased blood volume leads to a rise in blood pressure.
Therefore, aldosterone plays a crucial role in maintaining blood pressure and fluid balance.
Other Sites of Action
While the kidneys are the primary target, aldosterone also exerts its effects to a lesser extent on:
- Sweat glands: Influencing sodium reabsorption in sweat.
- Salivary glands: Affecting the sodium and potassium content of saliva.
- Intestines: Contributing to sodium and water absorption.
In Summary
Aldosterone is vital for maintaining electrolyte balance (especially sodium and potassium) and regulating blood pressure by controlling sodium and water reabsorption and potassium excretion in the kidneys and, to a lesser extent, in other tissues. Its actions are essential for maintaining proper fluid balance and cardiovascular function.
