Detection of a progesterone-induced secretory protein synthesized by the uteri but not the endometriotic implants of rats with induced endometriosis

Steroids modulate the secretory activity of the uterus, but little is known of their effect on ectopic endometrium protein synthesis and secretion. We utilized two-dimensional electrophoresis to visualize proteins produced by the uteri and endometriotic implants of both steroid-treated and reproductively cyclic rats with and without surgically induced endometriosis. Of the greater than 300 proteins visualized, only the uterine cultures from progesterone (P)-stimulated, estrogen-suppressed rats contained a distinctive glycoprotein (P-induced uterine protein-1; molecular weight [Mr] 70,000; isoelectric point [pI] 5.7). This protein was not detected in any of the endometriotic implant cultures. Progesterone-induced uterine protein-1 could play a role in luteal or endometrial physiology and may be valuable in assessing endometrial function. The aberrant secretory behavior of the ectopic endometrium suggests a possible involvement in the reproductive dysfunction associated with endometriosis.