Total urine output was measured by separately housing adult mice in Nalgene Metabolic Cages (Minimitter, Bend, Oregon, United States) for 2–3 d and collecting urine every 24 h period. Urine osmolalities were determined using an Osmometer (Osmette 5004; Precision Systems, Natick, Massachusetts, United States). Urine concentrating experiments were carried out by intraperitoneal injection of dDAVP (0.4 μg/kg). Mice were injected twice with dDAVP, once at time 0 and again at 30 min. Urine was collected at the start of the experiment and 30 min after the second injection.