Abstract
Aquaporins (AQPs) are a group of small, integral membrane proteins which play an important role in fluid homeostasis in the reproductive system. In our previous study, we demonstrated AQP1, 5 and 9 protein expression and localization in the porcine oviduct. The presence of these isoforms could suggest their role in the transport of the ovum to the uterus by influencing the epithelial cells’ production of oviductal fluid. The aim of this study was to evaluate the expression of AQP1, AQP5 and AQP9 in the infundibulum, ampulla and isthmus in the porcine oviduct during the estrous cycle (early luteal phase, days 2–4, medium luteal phase, days 10–12, late luteal phase days 14–16, follicular phase days 18–20) and pregnancy (period before implantation, days 14–16 and after the implantation, days 30–32) using the Real-Time PCR technique. As clearly demonstrated for the first time, AQP1, 5, and 9 gene expression is influenced by the estrus cycle and pregnancy. Furthermore, expression of AQPs in the porcine oviduct may provide the physiological medium that sustains and enhances fertilization and early cleavage-stage embryonic development. Overall, our study provides a characterization of oviduct AQPs, increasing our understanding of fluid homeostasis in the porcine oviduct to successfully establish and maintain pregnancy.
Highlights
Aquaporins (AQPs) belong to a family of intrinsic membrane proteins that act as selective channels for water and for solutes such as glycerol and urea
This result ties well with previous studies, wherein we found that in the oviduct of cyclic and pregnant gilts, the expression of AQP1, AQP5 and AQP9 proteins significantly increased on days 2–4 and 18–20 of the estrous cycle [9]
We recently found that PRL increased AQP5 mRNA and protein expression in the granulosa (GC) and theca cells (TC) obtained from medium (MF) and large follicles (LF) and in cocultures of these cells [23]
Summary
Aquaporins (AQPs) belong to a family of intrinsic membrane proteins that act as selective channels for water and for solutes such as glycerol and urea They play an important role in fluid homeostasis and the control of epithelial cell volume; expressions of AQPs have been proven in the reproductive system. We reported that aquaporins 1, 5 and 9 exist in the porcine oviduct in different stages of the cycle and early pregnancy under physiological conditions [8,9] They seem to be very important for the normal oviductal functions to maintain fluid homeostasis by influencing the epithelial cells’ production of oviductal fluid, which provides the physiological medium for fertilization and early embryonic development. Recent studies indicate that AQP5 specific to non-ciliated cells is activated during sexual maturation, supporting fluid homeostasis in the mouse oviduct [12]
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