Expression of dopamine receptors and transporter in neuroendocrine gastrointestinal tumor cells

C-11- or F-18-DOPA positron emission tomography (DOPA PET) is a new sensitive imaging technique for small neuroendocrine gastrointestinal tumors which evaluates the decarboxylase activity. To further characterize the dopaminergic system in neuroendocrine gastrointestinal tumor cells, we investigated...

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Bibliographic Details
Published in:Life sciences (1973) 2002-06, Vol.71 (6), p.667-678
Main Authors: Lemmer, K, Ahnert-Hilger, G, Höpfner, M, Hoegerle, S, Faiss, S, Grabowski, P, Jockers-Scherübl, M, Riecken, E.O, Zeitz, M, Scherübl, H
Format: Article
Language:English
Subjects:
2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine - pharmacology
Animals
Base Sequence
Biological Transport
cAMP
Carcinoid
Colforsin - pharmacology
Cyclic AMP - metabolism
DNA Primers
DOPA PET
Dopamine - metabolism
Dopamine - pharmacology
Dopamine Plasma Membrane Transport Proteins
Dopamine receptor
Dopamine transporter
Gastrointestinal Neoplasms
Gene Expression Regulation, Neoplastic
Humans
Membrane Glycoproteins
Membrane Transport Proteins - genetics
Mice
Nerve Tissue Proteins
Neuroendocrine Tumors - genetics
Pancreatic Neoplasms
Quinpirole - pharmacology
Receptors, Dopamine - genetics
Receptors, Dopamine D1 - genetics
Receptors, Dopamine D2 - genetics
Reverse Transcriptase Polymerase Chain Reaction
RNA, Messenger - genetics
Transcription, Genetic
Tumor Cells, Cultured
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Summary:C-11- or F-18-DOPA positron emission tomography (DOPA PET) is a new sensitive imaging technique for small neuroendocrine gastrointestinal tumors which evaluates the decarboxylase activity. To further characterize the dopaminergic system in neuroendocrine gastrointestinal tumor cells, we investigated the expression of both dopamine receptors and the transmembrane dopamine transporter (DAT) in the human neuroendocrine pancreatic cell line BON and in the neuroendocrine gut cell line STC-1. Both BON and STC-1 cells expressed mRNA of the dopamine receptors D2–D5 and DAT. mRNA of the dopamine receptor D1 was detected in BON cells only. Both in BON and STC-1 cells, expression of D2 and D5 receptors and DAT was also demonstrated immunocytochemically. For functional receptor characterization intracellular cAMP levels ([cAMP] i) were determined. Whereas in STC-1 cells dopamine and the D1-like (D1/D5) receptor agonist SKF 38393 increased [cAMP] i, [cAMP] i was decreased by dopamine or the D2-like (D2–D4) receptor agonist quinpirole in BON cells. Functional DAT activity was, however, not detected in either cell line. The presence of both dopamine receptors and of the DAT suggests an autocrine and/or paracrine function of dopamine in neuroendocrine gastrointestinal tumor cells. Yet neither the transmembrane dopamine transporter nor dopamine receptors are likely to contribute to positive DOPA PET imaging of neuroendocrine gastrointestinal tumors. However, these molecules may be of diagnostic importance when applying other dopaminergic system tracers.
ISSN:0024-3205
1879-0631
DOI:10.1016/S0024-3205(02)01703-4