Functional expression of aquaporins in fetal membranes from human term placenta.

DAMIANO A, LEVI L, ZOTTA E, IBARRA C

Santiago de Chile

Simposio; II Lati-American Symposium Materno-Fetal Interaction & Placenta: From Basic to Clinical Research; 2005

Sociedad Latinoamericana de Placenta

To be absorbed into the chorionic or placental circulation, amniotic fluid water and solutes must cross the avascular amniotic membrane, probably mediated by water channels. The expression of aquaporins (AQPs) 1, 3, 8 and 9 was previously described in fetal membranes. Noteworthy, AQP9 expression is regulated by endocrine factors. We also detected AQP7 by RT-PCR and immunohistochemistry. In this study, we characterize the functional expression of AQPs and its hormonal regulation. Methods: Human fetal membrane of term placentas obtained from cesarean were dissected and immediately mounted as a diaphragm in a Ussing chamber. The net trans-epithelial water flux (Jw) was recorded minute by minute by an equipment used currently in our laboratory. Results: In amnion and chorion, a similar absortive Jw [(0.35 ± 0.05) and (0.38 ± 0.07) µL. min-1.cm-2] was observed. These Jw were increased when an osmotic gradient was generated by adding (to the maternal side) different concentrations of poly(ethylene gycol) (Mr ~ 8000). The osmotic permeability (Posm) calculated was similar in both fetal membranes [(1.6 ± 0.3) vs (1.3 ± 0.3) 10-2 cm s-1] and they were significantly decreased (P<0.05, n=6) after preincubation with 0.3 mM HgCl2. Finally Jw increased [(0.61 ± 0.06) µL min-1 cm-2, P<0.05, n=4] when chorion was cultured during 24h with 300ng/mL progesterone (P4).This is the first study that reports the functionality of the AQPs present in the human fetal membranes and its up-regulation by P4. Conclusions: These results suggest that AQPs mediate water transport across fetal membranes and the activity of AQPs is promoted by P4. This hormonal mechanism indicates a potential regulation of amniotic fluid homeostasis. ANPCYT PICT 9508/02.