Abnormal function of the vasopressin-cyclic-AMP-aquaporin2 axis during urine concentrating and diluting in patients with reduced renal function. A case control study

Table 1 Urine concentrating test.

	24 hours urine collection without fluid deprivation (19.30 to 19.30)	12 hours urine collection with fluid deprivation (19.30 to 07.30)	One urine collection fluid deprivation(07.30-08.30)
U-osm (mosmol/l)
Group 1	561(357)	473(344)	823(213) *
Group 2	405(286)	369(460)	670(193) *
Group 3	472(303)	411(96)	547(223) *
Group 4	359(119)	351(126)	396(153) *
P (Kruskal-Wallis)	0.169	0.188	0.000
UV (ml/min)
Group 1	1.40(1.15)	1.08(1.02)	0.72(0.42) *
Group 2	1.91(1.26)	1.42(1.50)	0.97(0.94) *
Group 3	1.38(0.67)	1.69(0.41)	1.17(1.04)
Group 4	1.77(1.00)	1.84(0.67)	1.25(0.89) *
P (Kruskal-Wallis)	0.156	0.043	0.006
C _H20 (ml/min)
Group 1	-0,94(1.35)	-0,38(0.44)	-1.10(0.55)*
Group 2	-0,64(1.35)	-0,45(1.50)	-0,90(0.57) *
Group 3	-1.29(1.29)	-0,71(0.80)	-1,22(0.82)
Group 4	-0,28(0.84)	-0,13(0.73)	-0,30(0.66)
P (Kruskal-Wallis)	0.095	0.149	0.03
U-c-AMP (pmol/l)
Group 1	2.53(1.53)	3.00(2.27)	4.83(4.82)*
Group 2	2.01(0.96)	2.83(2.87)	4.79(4.67) *
Group 3	2.36(0.66)	1.96(0.95)	3.65(2.45)
Group 4	1.20(1.37)	1.31(1.02)	1.20(1.17)
P (Kruskal-Wallis)	0.000	0.000	0.000
U-AQP2 (ng/ml)
Group 1	0.68(0.88)	0.96(1.63)	0.72(1.26) *
Group 2	0.54(0.44)	0.51(0.98)	0.73(0.52) *
Group 3	1.13(0.47)	0.69(0.49)	0.87(0.33)
Group 4	0.79(0.63)	0.71(0.66)	0.63(0.61)
P (Kruskal-Wallis)	0.048	0.793	0.423

Urinary osmolarity (u-osm), urine volume (UV), free water clearance (C_H2O), urinary excretions of cyclic-AMP (u-c-AMP) and aquaporin2 (u-AQP2) in a 24 hours urine collection with unrestricted fluid intake, in an immediately following 12 hours urine collection with fluid deprivation (19.30 to 07.30), and in an immediately following one hour urine collection with fluid deprivation (07.30-08.30).
Group 1 comprised healthy control subjects (n = 10). Groups 2-4 comprised patients with chronic kidney disease or hypertension (Group 2 (n = 14), e-GFR ≥ 90 ml/min; Group 3 (n = 11), 60 ml/min ≤ e-GFR < 90 ml/min; and Group 4 (n = 16), 15 ml/min < e-GFR ≤ 60 ml/min).
Median with Interquartile Range in brackets. Kruskal-Wallis's test was used to analyze differences between groups during the concentration test. Wilcoxon's signed rank test was used to analyze differences in variables between baseline (24 hours urine) and the end of the test (one hours urine), * = P < 0.05.

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