Glomerulus Module

Renal Tubule Module
Afferent Arteriole
Proximal Tubule
Descending LOH
Ascending LOH
Macula Densa/
Distal Tubule
Collecting Ducts
Efferent Arteriole
Actions of Hormones


Chemical structure of
the steroid hormone.
Aldosterone functions to maintain an adequate ECV by regulating the amount of sodium reabsorbed in the tubule. Aldosterone is a steroid hormone produced in the glomerulosa cells of the adrenal cortex. By binding to the intracellular mineralocorticoid receptor, aldosterone changes the shape of the receptor allowing for DNA binding. This, in turn, leads to the production of new proteins that will serve to increase sodium reabsorption.

Although the exact mechanisms are not known, aldosterone increases the number of open sodium channels in the apical surface of principal cells. In addition, aldosterone increases the number of sodium-potassium pumps on the basolateral surfaces of these cells. (Aldosterone also acts on the thick ascending limb and the distal convoluted tubule, but its main effects are on the principal cells of the collecting ducts. Interestingly, aldosterone also acts on sweat glands to reduce the loss of sodium in perspiration acts on taste cells to increase the sensitivity of the taste buds to sources of sodium.)