AQP2 and Polyuria: Aquaporins, especially aquaporin-2 (APQ2), have a critical role in water regulation in the kidney.[9] A reduction of APQ2 or interference with its transport to the cell membrane plays an essential role in the development of polyuria associated with many of the acquired forms of NDI.[9,12,13] We hypothesized that in the process of infiltration, the secretion of matrix metalloproteinase by leukemic cells might injure or affect APQ2 expression, leading to increased water permeability of the cell membrane.