Detection of a unique 32-kd protein in the peritoneal fluid of women with endometriosis

OBJECTIVE: To test the hypothesis that endometriotic tissue secretes endometriotic-specific proteins into the peritoneal fluid (PF) of women with endometriosis. DESIGN: A prospective design was utilized in this study. SETTING: Tertiary care, university-based center and reproductive endocrinology laboratory. PARTICIPANTS: Women of reproductive age who were infertile with endometriosis (n = 19), as well as without endometriosis (n = 7), and fertile women undergoing tubal ligation (n = 6). INTERVENTIONS: Collection of PF fluid via laparoscopy. MAIN OUTCOME MEASURES: Peritoneal fluid proteins were isolated and assessed by two-dimensional polyacrylamide gel electrophoresis. RESULTS: Two-dimensional electrophoresis of PF proteins isolated a group of proteins (M(r) = 32 to 40 kd, pI = 4.5 to 5.2) in all PF samples that was similar to the rat endometriotic implant-specific protein, Endo-1. This group of proteins consisted of 5 to 12 individual proteins with endometriosis PF containing a significantly higher number of proteins (median = 11) compared with either PF from infertile women without endometriosis (median = 8) or from women undergoing tubal ligation (median = 7). In addition, one protein (M(r) = 32 kd, pI = 5.8), termed EPF-32, was detected predominantly (18 of 19 samples analyzed) in PF from women with endometriosis. This protein was also detected in PF from infertile women without endometriosis (2 of 7 samples) but not in the PF of fertile women undergoing tubal ligation (0 of 6 samples). The appearance of this protein was not associated with the severity of endometriosis. CONCLUSION: It is concluded from this study that PF from women with endometriosis predominantly contains a 32-kd protein (EPF-32) compared with the PF of women without the disease. The role of EPF-32 in the pathophysiology of endometriosis is not established but this protein may function as a diagnostic marker for endometriosis.