Background: This study is an attempt to construct a repository of polypeptide species in human uterine fluid during the mid-secretory phase of menstrual cycle. This information is essential to generate alternative and less invasive tools for the assessment of uterine functions.
Methods: Two-dimensional polyacrylamide gel electrophoresis (2D PAGE) and mass spectrometric analysis were used to resolve and identify the major components of human uterine fluid.
Results: Uterine fluid collected during the mid-secretory phase (n = 6) demonstrated ca. 590 polypeptide spots in the linear range of pH 4-7 after 2D PAGE. Mass spectrometric analysis revealed the presence of heavy and light chains of immunoglobulins, alpha-1 anti-trypsin precursor, anti-chymotrypsin precursor, haptoglobin, apolipoprotein A4, apolipoprotein A1 fragment, beta-actin fragment, heat shock protein 27, hemopexin precursor and transferrin precursor. 2D protein profile of fluid collected during the proliferative phase (n = 5) revealed ca. 433 polypeptide spots, of which 279 could be paired with mid-secretory phase protein spots on the basis of their coordinates (isoelectric point and molecular weight) in 2D gels. Apolipoprotein A4, apolipoprotein A1 fragment and alpha-1 anti-trypsin precursor were 2-3-fold more abundant in uterine fluid collected during the mid-secretory phase as compared with that in the proliferative phase. Further, 86 uterine fluid polypeptides were conserved across species, being detected in human, rat and bonnet monkeys.
Conclusions: The molecular repertoire of the mid-secretory phase human uterine fluid, when compared with that of the proliferative phase uterine fluid, is broadened due to differential expression of proteins. Further, some of the mid-secretory phase proteins were conserved across species.