(A) Twenty-four–hour urine volume collected by placing the rats in metabolic cages was not different between the groups (ALMS1-KO, 9.24 ± 0.72 ml, n = 5, vs. WT, 10.08 ± 0.78 ml, n = 4). (B) Urine osmolality measured in 24-hour urine collected sample was higher in ALMS1-KO rats (ALMS1-KO, 2,560 ± 63.4 mOsm/kg water, n = 5, vs. WT, 1,724 ± 73.1 mOsm/kg water, n = 3; *P < 0.005). (C) Urine volume measured 8 hours after 5 mg/kg bumetanide (submaximal dose) treatment was higher in ALMS1-KO rats (ALMS1-KO, 3.1 ± 0.32 ml/8 hours, n = 5, vs. WT, 1.6 ± 0.13 ml/8 hours, n = 4; *P < 0.025 vs. WT). (D) Urinary sodium excretion measured 8 hours after 5 mg/kg bumetanide treatment was higher in ALMS1-KO rats (ALMS1-KO, 485.2 ± 37.1 μmoles/8 hours, n = 5, vs. WT, 221.8 ± 32 μmoles/8 hours, n = 4; *P < 0.025 vs. WT). Values represent mean ± SEM, and statistical analysis was performed with 2-tailed Student’s t test and 2-way ANOVA.