title: Amino acid distribution and metabolism in pituitary adenomas using positron emission tomography with D-[11C]methionine and L-[11C]methionine.
abstract: Four patients with hormonally inactive pituitary adenomas were examined with positron emission tomography (PET) after injection, during different examinations, of L-[methyl-11C]methionine and D-[methyl-11C]methionine, respectively. After the rapid distribution phase, the enantiomer L-[11C]methionine, which is metabolically active, showed a considerable continuous irreversible trapping attributed to amino acid metabolism. The stereoisomer D-[11C]methionine, which does not participate in protein synthesis, showed a rapid distribution within the whole adenoma tissue, with a distribution space on the order of 100%. A minimal irreversible trapping was observed which could be explained by technical factors. It is concluded that PET using the two enantiomers allows a separation of passive distribution and metabolism, and that L-[11C]methionine can be used for in vivo quantitative studies of amino acid metabolism of pituitary adenomas.
mesh_terms: D000236:Adenoma / Q000000981:diagnostic imaging / Q000378:metabolism*; D000368:Aged; D000596:Amino Acids / Q000378:metabolism*; D002250:Carbon Radioisotopes; D006801:Humans; D007536:Isomerism; D008297:Male; D008715:Methionine; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism*; D014055:Tomography, Emission-Computed
chemical_list: D000596:Amino Acids; D002250:Carbon Radioisotopes; D008715:Methionine