The Effect of Oxytocin and an Oxytocin Antagonist on the Human Myometrial Proteome

Objective: The immediate effects of oxytocin on myometrial signal transduction have been described. However, the longer term effects (up to an hour) on the myometrial proteome have not. We combined in vitro contractility with proteomic analysis to determine the protein changes associated with oxytocin-induced myometrial activity. Study Design: Human myometrial biopsies were taken at elective caesarean section prior to administration of oxytocies. Strips were mounted in an organ bath and exposed to oxytocin (10(-8) mol/L), the oxytocin antagonist L373, 662 (10(-7) mol/L), or vehicle (n = 5 for each) for 60 minutes. Contractility was determined and expressed as a percentage of pretreatment for each strip. At the end of the contractility experiment, proteins were extracted and separated by two-dimensional (2D) gel electrophoresis. Two-dimensional gels were analyzed by PDQuest and proteins of interest identified by mass spectrometry. Results: Identified proteins that demonstrated differences as a result of treatment with oxytocin or the oxytocin receptor antagonist L373, 662 were Annexin-A3 Osteoglycin, HSP70-protein 2, 2 isoforms of Cytokeratin 19, Desmin, EHD2, Protein disulfide isomerase A3, BIGH3, transgelin, thioredoxin reductase, triose phosphate isomerase, pyruvate kinase, elongation factor 1 gamma, and alpha-Actin-3. These proteins can be grouped into 5 classes of protein, those associated with cytoskeletal function, contractile/oxidative stress, protein synthesis, extracellular matrix proteins, and energy metabolism. Conclusion: This study demonstrates that oxytocin has longer term (1 hour) effects on the myometrial proteome.