Regulation of Aldosterone - Essay Example

Download file to see previous pages Aldosterone secretion is regulated by multiple factors including the renin-angiotensin system (RAS), the level of K+ and Na+ ions in the blood, such hormones as ACTH, vasopressin, and somatostatin, serotonin, dopamine, atrial natriuretic peptide (ANP), β-adrenergic agents, etc (Wehling, 1995; Goodfriend, 2006).

Renin is an enzyme catalyzing the reaction of the transformation of angiotensinogen into angiotensin I. Angiotensin I is converted into angiotensin II and the last one is partially converted into angiotensin III (Wehling, 1995).

Both angiotensin II and III stimulate the synthesis of aldosterone by the adrenal glomerulosa layer. They bind to G-protein coupled receptors and stimulate the activity of phospholipase C and adenylate cyclase. This results in the increase of conversion of cholesterol to pregnenolone and corticosterone to aldosterone (Horton, 1994; Fuller, 2006).

The role of other factors is presented in the following table:

Increase of aldosterone synthesis

Decrease of aldosterone synthesis

Potassium

ACTH

Vasopressin

Sodium

Dopamine

Atrial natriuretic peptide (ANP)

Aldosterone controls electrolyte excretion and intravascular fluid volume. It acts on the mineralocorticoid receptors of the distal renal tubules and cortical collecting ducts of the kidneys. Aldosterone regulates such physiological mechanisms as resorption and excretion of electrolytes, particularly its action increases sodium resorption and potassium excretion. Sodium and water reabsorption is regulated by opening Na+ channels in the apical membranes of the tubular epithelium (Fuller, 2006; Rosansky, 2006). Correspondingly, opening K+ channels leads to increased potassium conductance from the cell and potassium excretion.

Aldosterone receptors are localized intracellularly. Their stimulation leads to DNA binding and changes in the transcription of genes.

Interestingly, aldosterone does not only participate in the regulation of blood pressure but it also influences the function of mononuclear leukocytes (Chai, 2005; Wehling, 1995).

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