鼠离体灌流心脏模型^125I-BMIPP与^125I-IPPA代谢的对比研究

Metabolism in the isolated rat heart： comparison of ^125I-BMIPP with ^125I--IPPA

目的比较侧链脂肪酸β-甲基碘苯脂十五烷酸（BMIPP）和直链脂肪酸碘苯脂十五烷酸（IPPA）在心肌代谢上的异同和特点。方法制备大鼠离体灌流心脏模型10只，分为2组，每组5只。基础灌流30min后，分别于灌流液中加入^125I-BMIPP和^125I-IPPA，持续灌流3h后取样灌流液，提取脂溶相处理后行薄层色谱法（TLC）和高压液相色谱法（HPLC）分析，并与加入被测物品初期（5min）的结果相比较。结果^125I-BMIPP灌流5min和3h后脂溶相提取放射性活度分别为注入剂量的99％和92％，而^125I-IPPA分别为95％和38％0125I-BMIPP灌流5min，HPLC分析放射性全部集中于保留时间37min段。3h后该处仍呈主峰，其前出现数个小峰，峰值分别对应于代谢产物甲基碘苯脂十四烷酸、对碘苯十二酸、对碘苯十酸、对碘苯八酸、对碘苯六酸、对碘苯四酸和对碘苯乙酸。^125I-IPPA灌流初期于HPLC保留时间33min段显示明显高峰，继续灌流3h后，该峰值消失。TLC测定^125I-BMIPPRf值为0．52，^125I-IPPA为0．45。3h后，85％的^125I-BMIPP仍集中于Rf值0．52处，在Rf值0．31前后有数个小峰。而^125I-IPPA持续灌流3h后酣值0．45处的峰消失，仅在原点发现放射性。结论^125I-BMIPP不被B氧化，能在心肌细胞内长时间滞留，便于观察脂肪酸在心脏内的分布状况。而^125I-IPPA代谢快速，可显示心肌中长链脂肪酸代谢氧化过程。

Objective The fatty acid metabolism in myocardium is recently one of the most interesting subjects in nuclear cardiology. The purpose of this study was to clarify the metabolic fate of ^125I--labeled 1 5- （p-iodopbenyl） -3- （ R, S） -methyl -pentadecanoic acid （ ^125I-BMIPP） and 1 5- （ p- ^125I] iodopbenyl） pentadecanoic acid （^125I-IPPA） by means of isolated rat hearts. Methods Ten isolated rat hearts were prepared and perfused with^125I-BMIPP （5 rats） or ^125I-IPPA （5 rats） for 3 h following a basic perfusion of 30 min. After perfusion, the radioactivity in the recirculated buffer was measured, The metabolites in the buffer were then extracted and analyzed using high performance liquid chromatography （HPLC） and thinlayer chromatography （TLC）. Results At the beginning （ 5 min） of ^125I-BMIPP perfusion, the main radioactive peak appeared on HPLC at 37 rain, which remained after 3 h perfusion. Several small peaks eluting were found before the parent peak at 30,26,21,16,12 and 9 rain, respectively. At the beginning （5min） of ^125I-IPPA perfusion, the main peak appeared on HPLC at 33 min, which disappeared after 3 h. Conclusions ^125I-BMIPP strongly inhibited beta-oxidation, therefore appeared suitable for myocardial metabolic imaging. ^125I-IPPA was metabolized rapidly.