DL-[Carboxyl-11C]tryptophan, a potential agent for pancreatic imaging; production and preclinical investigations.
In animal studies, DL-[carboxyl-14C]tryptophan [DL-Try(C-14)] showed a high specificity for the pancreas, which suggested the potential of DL-[carboxyl-11C]tryptophan [DL-Try(C-11)] for clinical pancreatic inaging. The blood clearance and tissue uptake of the amino acid were very rapid, and no carrier effect was observed through a dose of 5 mg/kg. None of three transplanted hamster pancreatic adenocarcinomas that we studied showed a selective uptake of DL-Try(C-14) by the tumor, and none of the three enzymatic regimens investigated gave significant enhancement of the pancreatic specificity. Commercial L-Try(C-14) gave slightly better pancreatic specificity than the analogous racemic compound but without enough improvement to warrant attempts at optical resolution. DL-Try(C-11) was synthesized in amounts up to 325 mCi using a rapid, high-temperature, high-pressure modification of the Bücherer-Strecker amino acid synthesis. Yields ranged from 30--60%, and a total of 40 min was required for synthesis and chromatographic purification. DL-Try(C-11) thus appears to have significant potential as a clinical pancreas-imaging agent, particularly when used in conjunction with positron computerized transaxial tomography.
D000230:Adenocarcinoma / Q000000981:diagnostic imaging; D000818:Animals; D002250:Carbon Radioisotopes; D002766:Cholecystokinin / Q000494:pharmacology; D006224:Cricetinae; D004285:Dogs; D005260:Female; D007553:Isotope Labeling; D008297:Male; D008647:Mesocricetus; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000000981:diagnostic imaging; D010179:Pancreas / Q000000981:diagnostic imaging*; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging; D011817:Rabbits; D011877:Radionuclide Imaging; D051381:Rats; D012633:Secretin / Q000494:pharmacology; D013268:Stimulation, Chemical; D014018:Tissue Distribution; D014184:Transplantation, Homologous; D014364:Tryptophan / Q000378:metabolism
D002250:Carbon Radioisotopes; D012633:Secretin; D014364:Tryptophan; D002766:Cholecystokinin