Synthesis of (11)C-M-l-SPD and its biodistribution in rats

Objective To explore the synthesis method of 11C-[2-O-CH3]-l-stepholidine( 11C-M-l-SPD) and evaluate its biodistribution in rats.Methods 11C-CH3-triflate was bubbled into the reactor of an automated remotely controlled radiosynthesizer module,which contained reaction materials in a V-tube.Twenty-five SD rats were randomly divided into 5 groups.Different organs (lung,heart,liver,spleen,stomach,intestine,kidney,muscle and brain) were excised at different time points (5,15,30,60 and 90 min)post-injection of 11 C-M-l-SPD (0.2 ml,22.2 MBq).Then the counts per minute of each organ were measured,and the ％ID/g was calculated.Biodistribution in different regions of the brain (frontal lobe,apical lobe,temporal lobe,occipital lobe,cerebellum,hippocampus,striatum,thalamencephalon and brain stem) was further evaluated.Analysis of variance was used for data analysis with SPSS 15.0.Results The synthesis time of 11C-M-l-SPD was 15 min.The overall radiochemical yield was 16％-34％.The product was colorless in a pH value of 6.5,and the radiochemical purity was more than 95％.Five min post-injection,the biodistribution of 11C-M-l-SPD reached high levels in the liver,kidney,heart,brain and lung,and then dropped quickly.Levels decreased clearly in most organs at 60 min after administration.The liver and kidney were the main excretory organs.The biodistribution of 11C-M-l-SPD in liver and kidney was (1.484±0.350)％ID/g and (1.323±0.153)％ID/g at 5 min after administration and went down to (0.478±0.039)％ID/g and (0.394 ±0.165)％ID/g at 90 min,respectively.Lower radioactivity was found in the stomach,spleen,intestine and muscle.The uptake of 11C-M-l-SPD in the brain reached a peak at 5 min after injection,and there was no significant differences in the brain regions (F=0.054,0.690,0.333,0.487,0.686,all P＞0.05).Conclusion The automatic synthesis of 11C-M-l-SPD is simple and fast,which provides the feasibility of its usage in PET imaging in vivo. Key words: L-SPD; Carbon radioisotopes; Isotope labeling; Pharmacokinetics; Rats