Synthesis of DTPA-attached estradiol derivative and determination of its radiopharmaceutical potential

Summary An estrogen derivative, β-estradiol or 1,3,5,(10)-estratriene-3,17β-diol) attached to diethylenetriamine pentaacetic acid (DTPA) was synthesized in six experimental steps. At the end of these steps, a DTPA-attached estradiol derivative called deoxy-demethyl homoestradiolyl-diethylenetriamine-pentaacetic acid (ESTDTPA) was obtained. The synthesized compounds were labeled with ^99mTc. Thin layer radio chromatography (TLRC) was used to determine radiochemical yields and stabilities.Structural investigations confirmed the structures. The labeling yield was satisfactory (about 95%), and ^99mTc-ESTDPTA was stable in neutral medium at room temperature for 5 hours. Biodistribution studies were performed on normal and DMBA-induced, tumor bearing female Albino Wistar rats. The activity per gram tissue was calculated, and time-activity curves were plotted. ESTDTPA uptake by uterus reached a level of 20.73% dose/g, showing a maximum within 5 minutes after injection. Ovary and breast showed similar biodistribution profiles. The kidneys, which are the primary organs of metabolism and excretion of estrogen, showed a high ^99mTc-ESTDTPA uptake. The imaging studies were performed on normal and tumor bearing female Albino Wistar rats using a Camstar XR/T gamma-camera. Gamma-scintigraphy studies showed that tumors could be well visualized in a few minutes and clearly differentiated from other organs, such as bladder and liver by 24 hours.