Estrogenic mimicry in the myometrium: BPA enhances uterine contractions and oxytocin response

Bisphenol A (BPA), a known xenoestrogen, is a synthetic compound commonly found in plastics, epoxy resins, and thermal paper. Due to its ability to activate estrogen receptors, BPA disrupts the delicate balance of the endocrine system. Because estrogen is known to increase the expression of oxytocin receptors in the myometrium, we hypothesized that the uteri of BPA-fed mice would experience a greater response to oxytocin than the uteri of mice fed a standard diet (SD), our control. To test this hypothesis, we tested the uteri of Non-Swiss Albino female mice (Charles River) fed the SD (Teklad Diets) and the BPA-diet, which consisted of 5mg BPA/kg of chow with fat composition similar that of SD chow. Four SD and four BPA diet female mice were euthanized at approximately 7 months of age. All animals were staged post-mortem, and body, uteri, ovaries, and gonadal fat weights were recorded. The uterine horns were dissected into 4 x10 mm strips and suspended in tissue baths containing Krebs solution (in mM, NaCl 117, KCl 4.7, NaHCO 3 25, MgCl 2 1.2, KH 2 PO 4 1.2, CaCl 2 2.5, glucose 11, pH= 7.4) at 37˚ C with continuous oxygenation (95% O 2 , 5% CO 2 ). After an initial challenge with 40 mM KCl in Krebs solution to establish maximal contractility for normalizing purposes, the strips were washed 3 times with normal Krebs. Then a dose-response to oxytocin (10-10 M to 10-5M) was performed. Area-Under-the-Curve, frequency, amplitude analysis, and statistical calculation (t-test) were conducted with SigmaPlot. Most of the animals tested were found to have been in diestrus. No significant difference in the body, uterine, ovarian, or gonadal fat weights was detected between the two groups. The spontaneous contractility of BPA-diet samples was twice as strong as that of SD strips. The maxima response and activation range (maximal response – minimal response) elicited by oxytocin were more powerful in BPA-diet uterine strips (P < 0.005 and P = 0.02, respectively). This difference seemed to be primarily determined by more pronounced changes in frequency in BPA-diet samples(P=0.002). Overall, our results suggest that prolonged exposure to BPA increases uterine contractility and the response to oxytocin, which supports our hypothesis that BPA might stimulate expression of oxytocin receptors in the uterus This study was supported by the Biomedical Sciences program at Midwestern University and MWU intramural grant to MP and startup funds to IMPV. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.