Protein repertoire of human uterine fluid during the mid-secretory phase of the menstrual cycle.

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.