AQP2 and Menkes disease: With recent evidence supporting the role of aquaporins [70], and specifically aquaporins 2, 4 and 5 in the pathogenesis of MD, it is relevant that aquaporin 5 is regulated by cyclic adenosine monophosphate (cAMP); other derivatives of adenosine, including adenosine triphosphate (ATP) play important roles in energy transfer.