Hartvig P, Agren H, Reibring L, Tedroff J, Bjurling P, Kihlberg T, Långström B
Hospital Pharmacy, University Hospital, Sweden.
J Neural Transm Gen Sect. 1991;86(1):25-41. doi: 10.1007/BF01250373.
The in vivo dopamine precursor L-3,4-dihydroxyphenylalanine (L-DOPA) labelled with 11C in the beta position has been used for positron emission tomography studies of L-DOPA utilization in the brain. The brain uptake and kinetics of L-[11C]DOPA-derived radioactivity were studied in healthy male volunteers, and the specific utilization, i.e. decarboxylation rate of L-[11C]DOPA in different brain areas, was quantified using a brain region devoid of specific L-[11C]DOPA utilization as reference. Total uptake of L-[11C]DOPA-derived radioactivity measured in the brain varied two- to three-fold between subjects, with highest radioactivity in the striatal region. Specific utilization of L-[11C]DOPA radioactivity in the striatal region and in the prefrontal cortex varied twofold between subjects. No specific utilization was observed in other regions of the brain. The uptake of radioactivity in the brain increased dose-dependently with the simultaneous administration of unlabelled L-DOPA up to 10 mg. On the other hand, a decrease in brain radioactivity uptake was measured after pretreatment with 1 mg/kg oral L-DOPA, indicating competition for transport across the blood-brain barrier. Benserazide 0.5 mg/kg orally increased somewhat the radioactivity uptake to the brain. None of these pharmacological perturbations demonstrated any clearcut effect on specific utilization of L-[11C]DOPA. Thus, 11C-labelled L-DOPA is introduced as an alternative to the well-established L-6-[18F]fluoro-DOPA methodology in clinical studies on brain L-DOPA uptake and dopamine synthesis.
β位用¹¹C标记的体内多巴胺前体L-3,4-二羟基苯丙氨酸（L-DOPA）已用于正电子发射断层扫描研究大脑中L-DOPA的利用情况。在健康男性志愿者中研究了L-[¹¹C]DOPA衍生放射性的脑摄取和动力学，并使用一个缺乏特异性L-[¹¹C]DOPA利用的脑区作为参考来量化不同脑区L-[¹¹C]DOPA的特异性利用情况，即脱羧率。在大脑中测量的L-[¹¹C]DOPA衍生放射性的总摄取量在不同受试者之间变化两到三倍，纹状体区域的放射性最高。纹状体区域和前额叶皮质中L-[¹¹C]DOPA放射性的特异性利用在不同受试者之间变化两倍。在大脑的其他区域未观察到特异性利用。同时给予高达10mg未标记的L-DOPA时，大脑中放射性的摄取呈剂量依赖性增加。另一方面，口服1mg/kg L-DOPA预处理后测量到大脑放射性摄取减少，表明存在跨血脑屏障转运的竞争。口服0.5mg/kg苄丝肼使大脑放射性摄取略有增加。这些药理学干扰均未对L-[¹¹C]DOPA的特异性利用产生任何明显影响。因此，在关于脑L-DOPA摄取和多巴胺合成的临床研究中，¹¹C标记的L-DOPA被引入作为成熟的L-6-[¹⁸F]氟多巴方法的替代方法。
