What is the effect of aldosterone on sodium levels?

Aldosterone is a steroid hormone produced by the adrenal cortex that plays a crucial role in regulating sodium and potassium levels in the body, particularly in the kidneys. One of its primary effects is to increase sodium reabsorption in the renal tubules.

When aldosterone is released, it binds to mineralocorticoid receptors in the cells of the distal convoluted tubule and the collecting ducts of the nephron. This binding stimulates the expression of various proteins, including sodium channels and sodium-potassium pumps. As a result, more sodium ions are reabsorbed from the tubular fluid back into the bloodstream, while potassium ions are secreted into the urine. This mechanism helps to maintain blood pressure and fluid balance, as increased sodium reabsorption leads to water retention and increased blood volume.

In summary, the correct answer indicates that aldosterone has a direct effect of increasing sodium reabsorption, thus contributing to the regulation of electrolyte balance and blood pressure in the body.