As there is more glucose in the collecting duct, the tubular
fluid becomes concentrated (high solute and less water).The water
tends to move from the area of high water content to
area of low water content.
ADH installs aquaporin water channels on the membrane of
epithelial cells in collecting duct. Aquaporins helps in
facilitated diffusion of water along the osmotic gradient. As
collecting duct fluid is more concentrated, the water remains in
the duct and cannot be removed out into interstital fluid.
Hence, due to presence high glucose, ADH cannot reduce fluid
volume in the collecting ducts.