NPPA and Polyuria: These findings signify that changes in serum levels of ANP and AVP are variable and not static, which implicates other important factors, such as corticosterone (increased urinary levels previously shown at 14 dpi) and/or key receptors/channels (V2R, NPRA, AQP2, and ENaC) in the kidney (altered levels previously shown at the 70-dpi time point).9,10 Although AVP and ANP are key regulators of water and solute balance and likely play a major role in SCI-induced polyuria, they are not the only factors involved in urine production.