<prompt> Vasopressin decreases the volume of urine primarily by causing:Decrease in glomerular filtration rateDecrease in renal blood flowDecrease in water permeability of descending limb of loop of HenleIncrease in water permeability of collecting duct cells  <response>: In the absence of ADH, collecting ducts are impermeable to water. ADH increases the exocytosis and decreases the endocytosis of water channels aquaporins in the collecting duct cells. This results in increase in permeability of collecting ducts to water. 