Determination of plasma [18F]-6-fluorodopa during positron emission tomography: elimination and metabolism in carbidopa treated subjects |
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| Authors: | B E Boyes P Cumming W R Martin E G McGeer |
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| Affiliation: | 1. 1st Department of Neurology, Aiginition University Hospital, National and Kapodistrian University of Athens, Vasilissis Sofias 72-74, Athens 115 28, Greece;2. 2nd Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Rimini 1, Chaidari 124 62, Greece;3. Center of Clinical Research, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Soranou Efesiou 4, Athens 115 27, Greece;4. Center of Systems Biology, Biomedical Research Foundation of the Academy of Athens, Soranou Efesiou 4, Athens 115 27, Greece;5. Taub Institute for Research in Alzheimer''s Disease and the Aging Brain, The Gertrude H. Sergievsky Center, Department of Neurology, Columbia University, 710 West 168th Street, New York, NY 10032, USA;1. Department of Pharmacy Practice, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok, Thailand;2. Departmeent of Pharmacy Practice, Daniel K. Inouye College of Pharmacy University of Hawai, HI, USA;3. Department of Pharmacology, Faculty of Pharmacy, Mahidol University, Bangkok, Thailand;4. Chulalongkorn Center of Excellence for Parkinson''s Disease and Related Disorders, Department of Medicine, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand |
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| Abstract: | An investigation of the metabolism of [18F]-6-fluorodopa (FDOPA) given to carbidopa treated subjects for scanning by positron emission tomography (PET) has been carried out by analysis of plasma. Reverse phase ion pair HPLC and alumina extraction were employed to fractionate and identify the [18F]-labelled compounds of plasma over a two hour period. During this time, the plasma levels of both total 18F and FDOPA decreased as a bi-exponential function of time. The rates of 18F, but not FDOPA, elimination were observed to decrease with age. In addition to FDOPA, only one other major peak of radioactivity was resolved by HPLC. Identification of this compound as the O-methylated derivative of FDOPA (MeFDOPA) is based on its shared HPLC elution time with in vitro synthesized O-[methyl-14C]-FDOPA. The ratio of the concentration of MeFDOPA to FDOPA (MeFDOPA/FDOPA) in plasma increased linearly with time, and the slope of this linear relationship decreased with the age of the individual. |
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