Receptor Specific Radiotracers For Imaging Dopamine And Estrogen Receptors

The preparation and evaluation of potential dopamine receptor imaging agents and an estrogen receptor imaging agent is the topic of this thesis. The dopamine (D-2) receptor imaging agent could be employed as a diagnosis tool for several neurological diseases and the estrogen receptor agent could be used to detect estrogen receptor positive tumors.;Three different monoiodinated derivatives of the haloperidol were synthesised as potential D-2 agents. The results of an in vitro competitive binding assay showed one derivative to have much higher affinity than the other two for D-2 receptors. This derivative was labelled with 131-iodine and biodistribution studies in rats were done to determine if selective uptake by D-2 receptors could be seen. However, over forty-eight hours no selectivity was observed.;A radioiodinating procedure based on the iododediazotization reaction was developed for preparing E and Z- ({dollar}\sp{lcub}131{rcub}{dollar}I) -iodotamoxifen (estrogen receptor agent) from the isolated diazonium salt. Presented are the results of a series of experiments in which various catalysts, diazonium salt counter ions, solvents and reaction conditions were tried. From these results a procedure was developed which allowed the preparation of 0.1 to 2.0 mCi (3.7 to 74 MBq) of ({dollar}\sp{lcub}131{rcub}{dollar}I) -iodotamoxifen in a 40 to 60 per cent radiochemical yield. The relative binding affinities of both the E and Z iodinated derivative and E and Z aminotamoxifen for estrogen receptors were determined in vitro. All four compounds showed some ability to bind, with Z-iodotamoxifen having the highest affinity and E-iodotamoxifen the lowest. The biological distributions of E and Z ({dollar}\sp{lcub}131{rcub}{dollar}I) -iodotamoxifen were determined in tumor-bearing mice. Selective uptake by both isomers was observed in the uterus and the tumors. In vivo, receptors binding was shown by a washout experiment with estradiol in mice. Also described are the results of a preclinical trial to determine E and Z- ({dollar}\sp{lcub}131{rcub}{dollar}I) -iodotamoxifen\u27s potential as tumor imaging agents. Unfortunately no uptake in known estrogen receptor positive tumors was observed