Automated synthesis of the ultra high specific activity of [11C]Ro15-4513 and its application in an extremely low concentration region to an ARG study.
We have designed and constructed an automated device for the production of ultra-high specific activity (11)C-labeled compounds via [(11)C]CH(3)I synthesized by the single pass I(2) method. The optimum condition for the production of [(11)C]CH(3)I was determined to be 630 degrees C for oven-1 (reaction column), 50 degrees C for oven-2 (iodine column) and 50 ml/min for the He gas flow rate, and gave the maximum conversion ratio of [(11)C]CH(3)I, 44%. [(11)C]Ro15-4513, known as an inverse agonist of the benzodiazepine receptor, was produced under optimized conditions. An i.v. injectable [(11)C]Ro15-4513 solution of 1500 +/- 490 MBq (n = 6) with specific activity 4700 +/- 2500 GBq/micromol and a radiochemical purity of 98.2 +/- 2% was obtained automatically within 25 minutes (from EOB) by irradiating nitrogen gas containing 5% H(2) with 18 MeV protons (14.2 MeV on target) at 20 microA for 20 minutes. The highest specific activity of 9700 GBq/micromol (at EOS) could be achieved, although the radiochemical purity was 92.4%. By the use of the ultra-high specific activity [(11)C]Ro15-4513, the super high affinity binding sites in the rat brain hippocampus could be clearly visualized even at the extremely low concentration of 0.66 pM Ro15-4513 by in vitro autoradiography.
Department of Medical Imaging, National Institute of Radiological Sciences, Chiba, Japan.
J
J
Noguchi
K
K
Suzuki
D000345:Affinity Labels / Q000138:chemical synthesis* / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D001386:Azides / Q000138:chemical synthesis* / Q000378:metabolism; D001569:Benzodiazepines / Q000138:chemical synthesis* / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D014055:Tomography, Emission-Computed
D000345:Affinity Labels; D001386:Azides; D001569:Benzodiazepines; C042957:Ro 15-4513