68Ga-Glutamate peptide-3 aminoethyl estradiol

Approximately 10% of women of reproductive age are affected by endometriosis, a gynecological disorder (1). Painful periods, pelvic pain, and infertility are often associated with endometriosis. Although a variety of mechanisms, including the roles of different cytokines, growth factors, and hormones, have been proposed in the development of endometriosis, the exact etiology and epidemiology of this condition is unclear (1-3). Menstruation in the opposite direction with spillage of viable endometrial cells into the peritoneum is often observed in cycling women (4). Adhesion, proliferation, and spread of the shed endometrial cells to the peritoneum are believed to support the development of endometriosis (5-7). Endometriosis is usually detected by a surgical technique such as a laparoscopy. Performing such a procedure on patients with infertility is often complex, and it provides information only about the morphological and anatomical changes in the tissue (8). Moreover, endometriosis usually progresses or recurs after surgery, and any relief to the patient is temporary (9). Because the prevalence and progression of endometriosis cannot be studied in humans without a laparoscopy, non-primate and primate animal models, including rabbits, have been used to investigate this disease (10-12). It has also been shown that estrogen receptors (ER) are overexpressed in the uterine endometrium and endometriotic lesions in endometriosis (4). In an effort to develop a non-invasive method to detect endometriosis, Takahashi et al. explored the use of estrogen, an ER ligand, to image endometriosis induced in rabbits (8). For this, estradiol (EDL) was conjugated to a glutamate peptide (GAP), which contained 5–10 glutamic acid residues, to facilitate the chelation of radioactive gallium (68Ga) to obtain 68Ga-GAP-EDL to image endometriosis.