The effect of progesterone on uterine fluid ph &endometrial nhe-1 protein expression in rats

Abstract

A precise regulation of the uterine fluid volume and pH is essential for a successful embryo implantation. Progesterone has been reported to participate in uterine fluid volume regulation during this period, however its effect on the uterine fluid pH is unknown. As endometrial fluid absorption has been proposed to occur secondary to sodium (Na+) absorption under progesterone mediated effect, we therefore hy-pothesize that there may be a concomitant changes in fluid volume and pH if sodium-hydrogen exchanger (NHE), a protein responsible for both luminal Na+ absorption and H+ extrusion is involved. In view of these, our study aimed to investigate the possibility that progesterone affect the uterine fluid pH and endometrial NHE expression. Ovariectomised female Sprague- Dawley (SD) rats were treated with peanut oil (vehicle), oestradiol-3-benzoate and progesterone for three consecutive days. On the fourth day, in-vivo uterine perfusions were performed on anaesthetized rats. The collected perfusate were analyzed for the changes in pH. The effect of amiloride, a non-specific Na+-channel blocker on the pH was investigated. The expression of uterine NHE-1 protein was detected by Western blotting and immunohistochemistry. Our findings indicate that the fluid pH is the lowest in progesterone-treated group and amiloride ad-ministration significantly increased the pH in the same treatment group (p < 0.05). NHE-1 proteins were significantly expressed in the progesterone-treated group. In conclusion, progesterone induces a reduction of the uterine fluid pH and is amiloride-sensitive. The up-regulation of NHE-1 under a common proge-sterone effect may explain the role of this ex-changer in regulating the uterine fluid pH.