Physiological water transport in human amnion is mediated by aquaporins

DI PAOLA MAURICIO; CASTRO-PARODI MAURICIO; IBARRA CRISTINA; DAMIANO ALICIA E

Mar del Plata

Simposio; VI LatinAmerican Symposium on Maternal-Fetal Interaction & Placenta; 2015

Latin American Society for Maternal Fetal Interaction and Placenta

Normal amniotic fluid (AF) is essential for fetal growth and development. Water absorption across fetal chorioamniotic membranes is a critical regulatory pathway for AF volume homeostasis. Four AQPs (AQP1, AQP3, AQP8 and AQP9) were described in human amnion. However, to date, no study has examined their functionality and only indirect evidence suggests that these proteins may be involved in the regulation of intramembranous absorption of AF. OBJETIVE: To evaluate if aquaporins mediate water flux in human amnion. METHODS: This study was approved by the ethics committee of the Hospital Nacional Dr. Prof. Alejandro Posadas, Argentina, and written consent was obtained from the patients. Human amnion were mounted as a diaphragm between two lucite chambers and the net transepithelial water movement (Jw) was recorded minute by minute with and without an osmotic gradient generated by adding 40 mOsm of polyethyleneglycol (Mr~ 8000) to the maternal side. HgCl2 was used as general inhibitor of AQPs. CuSO4, phloretin and tetraethylammonium (TEA) were used as specific blockers of AQP3, AQP9 and AQP1, respectively. Osmotic permeability was calculated using the values of Jw obtained with an osmotic gradient and after the addition of the inhibitors. RESULTS: An absortive Jw [(0.96±0.07) ìL.min-1.cm-2] was observed which increased when an osmotic gradient was generated. After general inhibition of AQPs with HgCl2, POsm decreased 65.2 ± 3.0%. TEA-inhibition of AQP1 showed a POsm reduction of 79.8 ± 1.4%, while treatments with CuSO4 and phloretin, to block AQP3 or AQP9, produced a POsm decrease of 51,8 ± 14,6% and 57.4±9.9 %, respectively. CONCLUSIONS: Our results strongly suggested that all the AQPs present in human amnion mediate the transcellular water transport. However, we found that AQP1 seems to contribute more to the water flux. Further studies are needed to evaluate the role of each AQP in the AF homeostasis.