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测量的显像剂。为此，我们开展了以下实验，以建立原位和在体的肝功能ESR成像技术。(1)用ESR光谱仪研究了NADPH诱导的大鼠肝微粒体中氮氧化物的还原。合成了四种不同位置含氮氧化物的硬脂酸，并将其掺入到微粒体膜中。比较了4种硬脂酸的还原速率，认为还原体系的活性中心应位于相应硬脂酸的7-12位。含氮磷脂的测定表明，微米体膜上的还原系统与磷脂酸发生了特异性的相互作用。(2)测定了环境空气对NADPH诱导的氧化还原系统的影响，测量了在N_2和O_2气体中微米体内ESR信号的变化。(3)活性氧的存在抑制了NADPH诱导的肝微粒体中ESR信号的还原。(4)静脉注射NADPH后，整个小鼠的肝区连续获得了体内和原位的ESR信号。估算了氮氧化物在肝脏中的清除量。(5)自制了ESR成像设备和程序。这一结果使得利用体内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.