Significance and expression of aquaporin-2 in fetus kidney and amniotic fluid at different stages of the pregnancy

Abstract

Objective To explore the expression of aquaporin-2(AQP-2) in human fetus kidney and amniotic fluid at different stages of pregnancy. Methods Twenty-two cases of aborted fetuses′ kidneys were collected.They were divided into 3 groups according to the pregnancy age: 8 cases in 17-23+ 6 weeks, 8 cases in 24-31+ 6 weeks, and 6 cases in 32-38+ 6 weeks.Western blot was used to examine the expression of AQP-2 in the kidney.Twenty-four cases of the amniotic fluid were collected, and they were divided into 3 groups according to the pregnancy age: 10 cases in 17-23+ 6 weeks, 6 cases in 24-31+ 6 weeks, and 8 cases in 32-38+ 6 weeks.Eight cases of healthy adult morning urine were collected as positive controls.The AQP-2 protein in the amniotic fluid was detected with the method of enzyme-linked immunosorbent assay (ELISA) and the osmotic pressure of amniotic fluid at different stages of the pregnancy was measured with the freezing point osmometer. Results The expression of AQP-2 was increased with the extending of pregnancy age, and the AQP-2 expressions in fetus kidney of 17-23+ 6 weeks, 24-31+ 6 weeks and 32-38+ 6 weeks were 0.986±0.335, 1.566±0.272, and 2.080±0.246, respectively, and the difference was significant(P<0.05). The AQP-2 detected from amniotic fluid was positively correlated with the result of AQP-2 in the kidney(r=0.985, P<0.05), and the AQP-2 expression also increased with the extending of pregnancy age: 17-23+ 6 weeks, 24-31+ 6 weeks, 32-38+ 6 weeks and adult urine was (30.253±5.843) mg/L, (35.103±7.271) mg/L, and (42.580±1.230) mg/L and (46.493±0.450) mg/L, respectively.The osmolality of the amniotic fluid of 17-23+ 6 weeks, 24-31+ 6 weeks, 32-38+ 6 weeks was (272.600±4.827) mmol/L, (252.00±15.360) mmol/L, and (261.750±5.560) mmol/L, respectively, and the difference was significant(P<0.05). Conclusions The AQP-2 expression in human fetus kidneys has good correlation with amniotic fluid, which indicates that the level of AQP-2 of the amniotic fluid may reflect the expression of AQP-2 in the fetus kidney. Key words: Aquaporin-2; Kidney; Amniotic fluid; Fetus