Dependence of Cardiac 11C-meta-Hydroxyephedrine Retention on Norepinephrine Transporter Density

Journal of Nuclear Medicine

Phillip S. Sherman¹  David M. Raffel¹  Wei Chen¹  David L. Gildersleeve¹  Yong-Woon Jung¹ 

[1] Division of Nuclear Medicine, Department of Radiology, University of Michigan Medical School, Ann Arbor, Michigan Division of Nuclear Medicine, Department of Radiology, University of Michigan Medical School, Ann Arbor, Michigan Division of Nuclear Medicine, Department of Radiology, University of Michigan Medical School, Ann Arbor, Michigan

关键词: sympathetic nervous system;    meta-hydroxyephedrine;    6-hydroxydopamine;    norepinephrine transporter;    PET;   

DOI  :  

学科分类：医学（综合）

来源: Society of Nuclear Medicine

【 摘 要 】

The norepinephrine analog 11C-meta-hydroxyephedrine (HED) is used with PET to map the regional distribution of cardiac sympathetic neurons. HED is rapidly transported into sympathetic neurons by the norepinephrine transporter (NET) and stored in vesicles. Although much is known about the neuronal mechanisms of HED uptake and retention, there is little information about the functional relationship between HED retention and cardiac sympathetic nerve density. The goal of this study was to characterize the dependence of HED retention on nerve density in rats with graded levels of cardiac denervation induced chemically with the neurotoxin 6-hydroxydopamine (6-OHDA). Methods: Thirty male Sprague–Dawley rats were divided into 6 groups, and each group was administered a different dose of 6-OHDA: 0 (controls), 7, 11, 15, 22, and 100 mg/kg intraperitoneally. One day after 6-OHDA injection, HED (3.7–8.3 MBq) was injected intravenously into each animal and HED concentrations in heart and blood at 30 min after injection were determined. Heart tissues were frozen and later processed by tissue homogenization and differential centrifugation into a membrane preparation for in vitro measurement of cardiac NET density. A saturation binding assay using 3H-mazindol as the radioligand was used to measure NET density (maximum number of binding sites [Bmax], fmol/mg protein) for each heart. Results: In control animals, NET Bmax was 388 ± 23 fmol/mg protein and HED heart uptake (HU) at 30 min was 2.89% ± 0.35 %ID/g (%ID/g is percentage injected dose per gram tissue). The highest 6-OHDA dose of 100 mg/kg caused severe cardiac denervation, decreasing both NET Bmax and HED HU to 8% of their control values. Comparing values for all doses of 6-OHDA, HED retention had a strong linear correlation with NET density: HU = 0.0077Bmax −0.028, r2 = 0.95. Conclusion: HED retention is linearly dependent on NET density in rat hearts that have been chemically denervated with 6-OHDA, suggesting that HED retention is a good surrogate measure of NET density in the rat heart. This finding is discussed in relation to clinical observations of the dependence of HED retention on cardiac nerve density in human subjects using PET.

【 授权许可】

Unknown