which hormone controls the amount of water reabsorption in the collecting ducts of the kidneys
Antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the circulation. In the absense of antidiuretic hormone, the collecting ducts are virtually impermiable to water, and it flows out as urine. Antidiuretic hormone stimulates water reabsorbtion by stimulating insertion of water channels or aquaporins into the membranes of kidney tubules.