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

稳定的氮氧化物自由基被广泛用作体内、原位和体外ESR测量的成像试剂。为此，本文开展了原位和体内ESR肝功能成像技术的研究。(1)用ESR谱仪研究nadph诱导的大鼠肝微粒体氮氧化物还原。合成了在不同位置携带氮氧化物的四种硬脂酸，并将其整合到微粒体膜中。4种硬脂酸的还原速率比较表明，还原体系的活性中心应该定位在对应硬脂酸的7- 12位。使用含氮氧化物磷脂的测量表明，在微粒体膜中，还原系统与磷脂酸发生了特定的相互作用。(2)测定了周围空气对nadph诱导氧化还原系统的影响，测定了N_2和O_2气体下微粒体ESR信号的变化。结果表明，在O_2条件下，相应的氮氧化物的还原态需要再氧化。(3)活性氧的存在抑制NADPH诱导的肝微粒体ESR信号降低。(4)静脉给药一氧化氮自由基后，在全鼠肝区连续获得体内和原位ESR信号。估计肝脏对氮氧化物的清除。(5)自行研制了电磁共振成像技术的设备和程序。结果使体内ESR成像技术测量肝功能成为可能。

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.