Sarah has been suffering from a stomach virus. As a result, she is dehydrated and her plasma ADH and aldosterone levels are elevated. Explain how each of these hormones independently affects the nephron including the specific location(s) of the nephron affected. Finally, state how the combined effects of these two hormones will alter urine concentration and volume

Answer 1

ADH will increase the number of aquaporins inserted into the apical plasma membrane of the distal convoluted tubule and collecting ducts. The presence of aquaporins will allow water to be reabsorbed by the osmotic gradient in this portion of the nephron to match the rising intramedullary concentration. Thus, the tubule fluid becomes very concentrated as water is removed. Aldosterone increases sodium reabsorption in the distal convoluted tubule and collecting duct. When sodium is reabsorbed water will follow to keep the osmotic gradient equal. Together, ADH and aldosterone yield significant water reabsorption in the late distal convoluted tubule and collecting ducts resulting in a small volume of highly concentrated urine.