Radiolabeled phenethylguanidines: novel imaging agents for cardiac sympathetic neurons and adrenergic tumors.
The norepinephrine transporter (NET) substrates [123I]-m-iodobenzylguanidine (MIBG) and [11C]-m-hydroxyephedrine (HED) are used as markers of cardiac sympathetic neurons and adrenergic tumors (pheochromocytoma, neuroblastoma). However, their rapid NET transport rates limit their ability to provide accurate measurements of cardiac nerve density. [11C]Phenethylguanidine ([11C]1a) and 12 analogues ([11C]1b-m) were synthesized and evaluated as radiotracers with improved kinetics for quantifying cardiac nerve density. In isolated rat hearts, neuronal uptake rates of [11C]1a-m ranged from 0.24 to 1.96 mL min-1 (g wet wt)-1, and six compounds had extremely long neuronal retention times (clearance T1/2 > 20 h) due to efficient vesicular storage. Positron emission tomography (PET) studies in nonhuman primates with [11C]1e, N-[11C]guanyl-m-octopamine, which has a slow NET transport rate, showed improved myocardial kinetics compared to HED. Compound [11C]1c, [11C]-p-hydroxyphenethylguanidine, which has a rapid NET transport rate, avidly accumulated into rat pheochromocytoma xenograft tumors in mice. These encouraging findings demonstrate that radiolabeled phenethylguanidines deserve further investigation as radiotracers of cardiac sympathetic innervation and adrenergic tumors.
Raffel
David M
DM
Division of Nuclear Medicine, Department of Radiology, 3480 Kresge III Building, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA. raffel@umich.edu
Jung
Yong-Woon
YW
Gildersleeve
David L
DL
Sherman
Phillip S
PS
Moskwa
James J
JJ
Tluczek
Louis J
LJ
Chen
Wei
W
D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging*; D000818:Animals; D002250:Carbon Radioisotopes; D006146:Guanidines / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D006147:Guanine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics; D006321:Heart / Q000000981:diagnostic imaging / Q000294:innervation*; D066298:In Vitro Techniques; D008253:Macaca mulatta; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009474:Neurons / Q000378:metabolism*; D050484:Norepinephrine Plasma Membrane Transport Proteins / Q000378:metabolism; D009655:Octopamine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics; D010673:Pheochromocytoma; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D051381:Rats; D013329:Structure-Activity Relationship; D013564:Sympathetic Nervous System / Q000166:cytology / Q000378:metabolism*; D014018:Tissue Distribution; D023041:Xenograft Model Antitumor Assays
C520643:4-hydroxyphenethylguanidine; D002250:Carbon Radioisotopes; D006146:Guanidines; C520642:N-guanyl-m-octopamine; D050484:Norepinephrine Plasma Membrane Transport Proteins; D019275:Radiopharmaceuticals; D009655:Octopamine; D006147:Guanine