Development of in situ liver function measurement with a L-band ESR imaging technique

稳定的氮氧自由基被广泛用作体内、原位和体外ESR测量的成像试剂。因此，本研究开展了以下实验，以发展原位和活体ESR肝功能显像技术。(1)用ESR波谱仪研究了NADPH诱导的大鼠肝微粒体氮氧自由基还原。合成了四种在不同位置具有氮氧自由基的硬脂酸，并将其掺入微粒体膜中。通过对4种硬脂酸的还原速率比较，认为该体系的还原活性中心位于硬脂酸的7~12位。使用磷脂轴承氮氧化物的测量表明发生的还原系统与磷脂酸在微粒体膜的特定相互作用。(2)本文通过观察N_2和O_2气氛下微粒体ESR信号的变化，研究了环境空气对NADPH诱导的氧化还原系统的影响。发现还原态氮氧自由基在O_2气氛下应再氧化。(3)活性氧的存在抑制了NADPH诱导的肝微粒体ESR信号降低。(4)在静脉注射氮氧自由基的全鼠肝区连续获得了体内和原位ESR信号。估算了肝脏中氮氧化物的肝脏清除率。(5)ESR成像技术的设备和程序是自行研制的。本研究结果为在体ESR显像技术检测肝功能提供了可能。

Stable nitroxide radicals are widely used as imaging reagents for in vivo, in situ, and in vitro ESR measurements. Thus the following experiments were carried out to develop in situ and in vivo ESR imaging technique of liver function.(1) NADPH-induced nitroxide reduction in rat liver microsomes was investigated with an ESR spectrometer. Four stearic acids bearing nitroxide at a different position were synthesized and incorporated into the microsomal membranes. Comparison of reduction rate among 4 stearic acids suggested that the active center of the reduction system should be localized at 7- 12th position of the corresponding stearic acid. The measurements using phospholipids bearing nitroxide indicated the occurrence of a specific interaction of the reduction system with phosphatidic acid in microsomal membranes.(2) The effects of surrounding air on NADPH-induced redox system was measured the change of ESR signal in microsomes under N_2 and O_2 gas. It was found that reduced form of the corresponding nitroxide should be reoxidized under O_2.(3) The presence of active oxygen suppressed ESR signal reduction induced with NADPH in liver microsomes.(4) In vivo and in situ ESR signals were successively obtained in the hepatic domain of whole mouse intravenously administered with nitroxide radical. The hepatic clearance of nitroxide in liver was estimated.(5) The equipments and programs for an ESR imaging technique were manufactured by ourselves. The results made it possible to measure liver function with in vivo ESR imaging technique.