In vivo detection of a pH-sensitive nitroxide in the rat stomach by low-field ESR-based techniques
In vivo detection of a pH-sensitive nitroxide in the rat stomach by low-field ESR-based techniques
复制标题
DOI：
10.1002/mrm.10392
复制
发表时间：
2003-03-01
影响因子：
3.3
通讯作者：
Nicholson, I
中科院分区：
文献类型：
--
作者：
Foster, MA;Grigor'ev, IA;Nicholson, I
研究了pH敏感的咪唑烷自旋探针的体内可检测性，以及基于低频电子自旋共振（ESR）的技术在大鼠体内和体外pH测量的有效性。所使用的技术是磁共振检测ESR（LODESR）和场循环动态核极化（FC-DNP）的体外和体内测量，射频（RF）和X-波段ESR的比较在体外。自旋探针是pK为4.6的六甲基咪唑烷（HMI）。所有技术均检测到HMI。通过FC-DNP的检测意味着自由基和溶剂水自旋之间的耦合。相对于测量频率，氮氧自由基的三条光谱线之间的分离与理论一致。未质子化HMI（pH > pK）的总光谱宽度大于质子化试剂（pH < pK）的总光谱宽度。这在体外和体内都观察到了。长期研究表明，HMI是可检测的，并且具有相同的光谱宽度（即，在相同的pH下），但在第一个小时内信号幅度迅速下降。这些发现证明了LODESR和FC-DNP用于监测HMI和测量体内pH值的适用性。这些技术将是有用的监测疾病和药物药理学在生活系统。(C)2003 Wiley-Liss，Inc.
A study was made of the in vivo detectability of a pH-sensitive, imidazolidine spin probe, and the efficacy of low-frequency electron spin resonance (ESR)-based techniques for pH measurement in vitro and in vivo in rats. The techniques used were longitudinally-detected ESR (LODESR) and field-cycled dynamic nuclear polarization (FC-DNP) for in vitro and in vivo measurements, and radiofrequency (RF)- and X-band ESR for comparisons in vitro. The spin probe was hexamethyl imidazolidine (HMI) with a pK of 4.6. All techniques detected HMI. Detection by FC-DNP implies coupling between the free radical and solvent water spins. Separations between the three spectral lines of the nitroxide radical, relative to measurement frequency, were consistent with theory. The overall spectrum width from unprotonated HMI (pH > pK) was greater than that from protonated agent (pH < pK). This was observed in vitro and in vivo. Longer-term studies showed that HMI is detectable and has the same spectral width (i.e., is at the same pH) up to 2 hr after gavage into the stomach, although the magnitude of the signal decreases rapidly during the first hour. These findings demonstrate the suitability of LODESR and FC-DNP for monitoring HMI and measuring pH in vivo. These techniques would be useful for monitoring disease and drug pharmacology in the living system. (C) 2003 Wiley-Liss, Inc.