Table 1. The daytime defect in urine concentration in Fxyd1^-/- mice was compensated over 24 h.

24 hour urine collection	WT	KO	Statistical significance
mOsm/30g	3,117 ± 126, n = 18	3,442 ± 219, n = 18	P = 0.21
volume, ml/30 g	1.32 ± 0.13, n = 19	1.24 ± 0.12, n = 19	P = 0.67
water intake, ml/30 g	4.62 ± 0.33, n = 18	4.56 ± 0.29, n = 18	P = 0.89

Osmolality was measured in urine collected from male mice in metabolic cages and is expressed as mean ± SEM. N is the number of mice, and osmolality of each sample was measured in duplicate. In one experiment with females (five WT and five KO), urine osmolality was measured in five consecutive daily urine samples, and like the males, there was no significant difference between WT and KO (data not shown). Significance was evaluated by Student’s t-test.