Polypeptides synthesized and released by rat ectopic uterine implants differ from those of the uterus in culture

Unique endometriosis-specific secretory proteins would be of paramount importance as noninvasive markers for diagnosis and evaluation of therapeutic approaches for endometriosis. Furthermore, identification of endometriosis-specific secretory proteins may be an important step towards understanding the pathophysiology of endometriosis-associated pain and infertility. Therefore this study was designed to assess protein synthesis and secretion by ectopic uterine implants from steroid-treated and reproductively cyclic rats with surgically induced endometriosis. Uteri, ectopic uterine implants, and control tissues were incubated in L-[35S]methionine or D-[6-3H]glucosamine for 0-24 h and 24-48 h. De novo-synthesized proteins released into the culture media were identified using two-dimensional SDS-PAGE, fluorography, and computer-assisted image analysis. Two distinct groups of ectopic uterine implant proteins were identified: ENDO I (M(r) 40,000-50,000; pI 4.0-5.2) and ENDO II (M(r) 28,000-32,000; pI 7.5-9.0) were produced by ectopic uterine implants and not the uteri. A third group of proteins, previously identified in culture media of the uteri from progesterone-treated rats and called PUP-1 (M(r) 70,000; pI 5.7), was synthesized and secreted by ectopic uterine implants 24-48 h later than in parallel uterine cultures. The detection of ectopic uterine implant proteins suggests biochemical characteristics of the ectopic tissue that may be used to develop unique markers for endometriosis. Furthermore, the delayed synthesis and secretion of the uterine protein PUP-1 by the ectopic uterine implants illustrates yet another example of the asynchronous behavior of these two tissues, which may be related to the etiology or pathophysiology of the disease.