Possible roles of aquaporins and fetuin-B in the preterm delivery in the rat

E Ducza, A Seres, R Gáspár, G Falkay. University of Szeged, Department of Pharmacodynamics and Biopharmacy, 6720, Hungary

The aquaporins (AQPs) are a family of integral membrane channel proteins that facilitate rapid passive movement of water. Earlier we investigated the mRNA expressions in different types of AQPs during pregnancy. We found, that the expression of AQP5 mRNA was the highest on pregnancy days 18-21 and dramatically decreased on the last day of pregnancy (day 22) in the rat.

Fetuin-B is an inhibitor of basic calcium phosphate, preventing unwanted calcification. The low level of fetuin could be associated with an increased risk of atherosclerosis and ectopic microcalcifications in soft tissues. According to the pharmacological logic we suppose a possible correlation between the calcification (fetuin-B) and the water movement (AQP) in the pregnant uterus near the time of delivery.

Our aims were (1) to examine the alterations of mRNA expression of the fetuin-B in the late pregnant rat uterus, furthermore (2) to investigate the AQP5 and fetuin-B expression in hormonally- and LPS- (lipopolysaccharide) induced preterm labour.

Changes in AQP5 and fetuin-B mRNA expression were measured by real-time PCR on pregnancy days 18, 20, 21 and 22 in rat uterus and after induction of preterm delivery with mifepristone and prostaglandin E2 or LPS treatment.

The fetuin-B mRNA expression – like to AQP5 - was the highest on days 20 which was significantly decreased on the last day of pregnancy (Relative quantitation/RQ20 = 15,76 and RQ22 = 5,72; ***, p<0,001, n=6). In hormonally-induced preterm labour, the mRNA expression of AQP5 and fetuin-B markedly decreased similarly to the last day of pregnancy (***, p<0,001, n=6). On the other hand, the fetuin-B expression increased in the inflammatory preterm birth induced by LPS (RQLPS = 11,45; ***, p<0,001, n=6).

We suppose that decreased expression of AQP5 and fetuin-B may have importance in the initiation of delivery in rat. Additionally, the differences between the AQP5 and fetuin-B level in different preterm model can be diagnostic value for reasons of the preterm birth.

Significant changes in the expression of these proteins in the term or preterm delivery may be useful in the diagnosis of delivery and preterm delivery.

Further studies are required to clarify whether AQPs and fetuin-B have some direct cooperation in the control of delivery or preterm birth.

This work was supported by the New Hungary Development Plan (TÁMOP-4.2.1/B-09/1/KONV-2010-0005 – Creating the Center of Excellence at the University of Szeged)