QS Study

Aldosterone is produced in the cortex of the adrenal glands, which are located above the kidneys. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It affects the body’s ability to regulate blood pressure. It balances the levels of sodium and potassium in your body.

Mechanism of action of Aldosterone – It is a type of steroid hormone that acts mainly in renal collecting ducts to stimulate reabsorption of Na+ as well as secretion of K+ and H+.

(1) Diffusion of aldosterone to the interior of cells

Because of lipid solubility, aldosterone diffuses readily to the interior of the tubular epithelial cells.

(2) Binding of aldosterone with its intracellular receptor:

Aldosterone binds with highly specific cytoplasmic receptor protein.

(3) Transcription:

Aldosterone – Receptor complex binds or activates the specific portion of DNA, in turn, initiates transcription of specific genes to form messenger RNA.

Fig: Mechanism of action of Aldosterone

(4) Molecular Mechanism:

Like all steroid hormones, aldosterone mediates its effect in responsive cells by binding cellular nuclear receptors which are then stimulated to transcribe a variety of specific target genes.

(5) Physiological Effects

The most important physiological effect of aldosterone is stimulation of sodium resorption and potassium secretion by principal cells of the late distal tubule and collecting duct.

(6)Translation:

mRNA diffuses into the cytoplasm where it promotes the translation process to produce the following types of protein –

(a) One or more enzyme protein; Such as Na+ – K+ ATPase,

(b) Membrane transport proteins (channel protein)

Channel proteins – present on luminal membrane allows rapid diffusion of Na+ from the lumen to cell; Na+ has pumped the rest of the way by Na+ – K+ Pump located in the basolateral membrane of the cell out of the cell into the interstitium.