Expression and localization of aquaporin 1 and 3 in human fetal membranes.
OBJECTIVE
Aquaporins are a family of water-selective channels that facilitate fluid movement across cell membranes. Specifically, aquaporin 1 (AQP1) and aquaporin 3 (AQP3) have been found to be important in osmotic water movement across membranes. Our goal in this study was (1) to determine whether AQP1 or AQP3 messenger RNA are expressed in the chorioamniotic membrane and, if present, (2) to determine the precise membrane location of these aquaporins.


METHODS
Placentas were collected from women with intact membranes not in labor who underwent elective cesarean sections at term (37-40 weeks). The membranes (amnion and chorion) directly overlying the placenta were sampled as well as the free-floating reflected membranes. RNA and protein were isolated from the amnion and chorion. Reverse transcriptase-polymerase chain reaction, Western analysis, and immunohistochemistry were used to determine expression and localization of AQP1 and AQP3.


RESULTS
AQP1 messenger RNA was found in amnion and chorion from both membrane locations. Western analysis also yielded positive results for amnion and chorion from both locations. Immunohistochemical localization of AQP1 showed it to be present on the apical aspect of the chorionic plate amnion. AQP3 protein was not found in the fetal membranes.


CONCLUSIONS
AQP1 is present in the fetal membranes. AQP1 may play a role in water movement from the amniotic cavity across the placenta into the fetal circulation. Further studies are needed to clarify our understanding of the role of fetal membrane aquaporins in amniotic fluid homeostasis.
Mann
Stephanie E
SE
Department of Obstetrics, School of Medicine, University of California-San Francisco, 1001 Potrero Avenue 6D13, San Francisco, CA 94110, USA.
Ricke
Emily A
EA
Yang
Baxoue A
BA
Verkman
Alan S
AS
Taylor
Robert N
RN
D000650:Amnion / Q000378:metabolism*; D051398:Aquaporin 1; D051400:Aquaporin 3; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D001789:Blood Group Antigens; D015153:Blotting, Western; D002823:Chorion / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014018:Tissue Distribution
C496020:AQP1 protein, human; C496027:AQP3 protein, human; D020346:Aquaporins; D001789:Blood Group Antigens; D012333:RNA, Messenger; D051398:Aquaporin 1; D051400:Aquaporin 3