Oxytocin regulates the expression of aquaporin 5 in the late‐pregnant rat uterus

Abstract

SUMMARYAquaporins (AQPs) are integral membrane channels responsible for the transport of water across a cell membrane. Based on reports that AQPs are present and accumulate in the female reproductive tract late in pregnancy, our aim was to study the expression of AQP isoforms (AQP1, 2, 3, 5, 8, and 9) at the end of pregnancy in rat in order to determine if they play a role in parturition. Reverse-transcriptase PCR revealed that specific Aqp mRNAs were detectable in the myometrium of nonpregnant and late-pregnancy (Days 18, 20, 21, and 22 of pregnancy) rat uteri. The expression of Aqp5 mRNA and protein were most pronounced on Days 18À21, and were dramatically decreased on Day 22 of pregnancy. In contrast, a significant increase was found in the level of Aqp5 transcript in whole-blood samples on the last day of pregnancy. The effect of oxytocin on myometrial Aqp5 expression in an organ bath was also investigated. The level of Aqp5 mRNA significantly decreased 5 min after oxytocin (10 À8 M) administration, similarly to its profile on the day of delivery; this effect was sensitive to the oxytocin antagonist atosiban. The vasopressin analog desmopressin (3.7 Â 10 À8 M), on the other hand, did not alter the expression of Aqp5, but did increased the amount of Aqp2 mRNA, an effect that was atosiban-resistant. These results lead us to propose that oxytocin selectively influences the expression of Aqp5 at the end of pregnancy, and may participate in events that lead to parturition in the rat. The sudden increase of AQP5 in the blood on the last day of pregnancy may serve as a marker that indicates the initiation of delivery.Mol. Reprod. Dev. 81: 524À530,

Expression of Aquaporin 1 and 5 and Their Regulation by Ovarian Hormones, Arachidonic Acid, Forskolin and cAMP During Implantation in Pigs

“…The present experiments showed that OT increased AQP1 mRNA expression after 24-h and decreased AQP5 mRNA after 3 and 24 h incubation, but had no effect on AQP1 or AQP5 protein content. These results partially are in agreement with the data obtained very recently by Ducza et al (2014). They indicated that OT treatment increased AQP2 mRNA levels but also specifically reduced the expression of AQP5 in the rat uterus on Day 18 of pregnancy.…”

“…Here, we can hypothesize that regulation of AQPs expression seemed to occur at the post-transcriptional level as protein expression upon Western-blot was pronounced. Further, those inverse relations are not accidental, they also happened in other studies performed by Klein et al (2013) and Ducza et al (2014). Therefore, it is not clear how tightly transcription and translation are correlated during such development processes.…”

The Effects of Female Sexual Hormones on the Expression of Aquaporin 5 in the Late-Pregnant Rat Uterus

“…In our earlier studies, it was determined that AQP5 expression shows the highest value on day 18 of pregnancy, and a remarkable decrease was found on the last day of pregnancy in rats [22]. …”

“…The presence of a copulation plug or the presence of sperm in the native vaginal smear was accepted as proof of the mating. These female animals were separated and regarded as first-day pregnant rats [22,35]. …”

“…We determined the effect of oxytocin on the myometrial expression of AQP5. Our results led us to suppose that oxytocin selectively decreases the expression of AQP5 at the end of pregnancy and may be of importance in the initiation of delivery in rats [22]. …”