Radiolabeled phenethylguanidines: novel imaging agents for cardiac sympathetic neurons and adrenergic tumors.

Abstract

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.

• Authors: David M Raffel, Yong-Woon Jung, David L Gildersleeve, Phillip S Sherman, James J Moskwa, Louis J Tluczek, Wei Chen
• Journal: Journal of medicinal chemistry (J Med Chem) Vol. 50 Issue 9 Pg. 2078-88 (May 03 2007) ISSN: 0022-2623 [Print] United States
• PMID: 17419605 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• 4-hydroxyphenethylguanidine
• Carbon Radioisotopes
• Guanidines
• N-guanyl-m-octopamine
• Norepinephrine Plasma Membrane Transport Proteins
• Radiopharmaceuticals
• Octopamine
• Guanine

Topics

• Adrenal Gland Neoplasms (diagnostic imaging)
• Animals
• Carbon Radioisotopes
• Guanidines (chemical synthesis, chemistry, pharmacokinetics, pharmacology)
• Guanine (analogs & derivatives, chemical synthesis, chemistry, pharmacokinetics)
• Heart (diagnostic imaging, innervation)
• In Vitro Techniques
• Macaca mulatta
• Male
• Mice
• Mice, Nude
• Neurons (metabolism)
• Norepinephrine Plasma Membrane Transport Proteins (metabolism)
• Octopamine (analogs & derivatives, chemical synthesis, chemistry, pharmacokinetics)
• Pheochromocytoma
• Positron-Emission Tomography
• Radiopharmaceuticals (chemical synthesis, chemistry, pharmacology)
• Rats
• Structure-Activity Relationship
• Sympathetic Nervous System (cytology, metabolism)
• Tissue Distribution
• Xenograft Model Antitumor Assays