What does aldosterone do when it acts on the kidneys? (Choose 2)

Aldosterone is a steroid hormone produced by the adrenal glands that plays a crucial role in regulating sodium and potassium balance as well as fluid balance in the body. When aldosterone acts on the kidneys, it primarily acts on the cells of the distal convoluted tubule and the collecting duct. One of its primary functions is to promote the reabsorption of sodium (Na+) from the filtrate back into the bloodstream. This process not only increases sodium retention but also has a direct effect on water retention, as water follows sodium osmotically.

By increasing sodium reabsorption, aldosterone leads to an increase in total body sodium levels, which contributes to an increase in fluid volume, thereby increasing blood pressure as well. Furthermore, when sodium is retained, this influences the retention of water, promoting fluid retention in the body and helping to maintain blood pressure and overall fluid balance.

Thus, the correct answer highlights that aldosterone increases sodium retention in the kidneys, which is fundamental to its role in fluid homeostasis.