Radiosynthesis and Preclinical Evaluation of an α-Adrenoceptor Tracer Candidate, 6-[F]Fluoro-marsanidine
Molecular Imaging and Biology, ISSN: 1860-2002, Vol: 21, Issue: 5, Page: 879-887
2019
- 4Citations
- 12Captures
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Example: if you select the 1-year option for an article published in 2019 and a metric category shows 90%, that means that the article or review is performing better than 90% of the other articles/reviews published in that journal in 2019. If you select the 3-year option for the same article published in 2019 and the metric category shows 90%, that means that the article or review is performing better than 90% of the other articles/reviews published in that journal in 2019, 2018 and 2017.
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Metrics Details
- Citations4
- Citation Indexes4
- CrossRef3
- Captures12
- Readers12
- 12
Article Description
Purpose: The α-adrenoceptors mediate many effects of norepinephrine and epinephrine, and participate in the regulation of neuronal, endocrine, cardiovascular, vegetative, and metabolic functions. Of the three receptor subtypes, only α and α are found in the brain in significant amounts. Subtype-selective positron emission tomography (PET) imaging of α-adrenoceptors has been limited to the α subtype. Here, we report the synthesis of 6-[F]fluoro-marsanidine, a subtype-selective PET tracer candidate for α-adrenoceptors, and its preclinical evaluation in rats and mice. Procedures: 6-[F]Fluoro-marsanidine was synthesized using electrophilic F-18 fluorination with [F]Selectfluor bis(triflate). The tracer was evaluated in Sprague Dawley rats and in α-knockout (KO) and wild-type (WT) mice for subtype selectivity. In vivo PET imaging and ex vivo brain autoradiography were performed to determine the tracer distribution in the brain. The specificity of the tracer for the target was determined by pretreatment with the subtype-non-selective α-agonist medetomidine. The peripheral biodistribution and extent of metabolism of 6-[F]fluoro-marsanidine were also analyzed. Results: 6-[F]Fluoro-marsanidine was synthesized with [F]Selectfluor bis(triflate) in a radiochemical yield of 6.4 ± 1.7 %. The molar activity was 3.1 to 26.6 GBq/μmol, and the radiochemical purity was > 99 %. In vivo studies in mice revealed lower uptake in the brains of α-KO mice compared to WT mice. The results for selectivity were confirmed by ex vivo brain autoradiography. Blocking studies revealed reduced uptake in α-adrenoceptor-rich brain regions in pretreated animals, demonstrating the specificity of the tracer. Metabolite analyses revealed very rapid metabolism of 6-[F]fluoro-marsanidine with blood-brain barrier-permeable metabolites in both rats and mice. Conclusion: 6-[F]Fluoro-marsanidine was synthesized and evaluated as a PET tracer candidate for brain α-adrenoceptors. However, rapid metabolism, extensive presence of labeled metabolites in the brain, and high non-specific uptake in mouse and rat brain make 6-[F]fluoro-marsanidine unsuitable for α-adrenoceptor targeting in rodents in vivo.
Bibliographic Details
http://www.scopus.com/inward/record.url?partnerID=HzOxMe3b&scp=85060940077&origin=inward; http://dx.doi.org/10.1007/s11307-019-01317-6; http://www.ncbi.nlm.nih.gov/pubmed/30710261; http://link.springer.com/10.1007/s11307-019-01317-6; https://dx.doi.org/10.1007/s11307-019-01317-6; https://link.springer.com/article/10.1007/s11307-019-01317-6
Springer Science and Business Media LLC
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