Wolber J, Cherubini A, Leach M O, Bifone A
CRC Clinical Magnetic Resonance Research Group, The Institute of Cancer Research, The Royal Marsden NHS Trust, Sutton, Surrey SM2 5PT, UK.
NMR Biomed. 2000 Jun;13(4):234-7. doi: 10.1002/1099-1492(200006)13:4<234::aid-nbm632>3.0.co;2-k.
The spin-lattice relaxation time, T(1), of hyperpolarized (129)Xe in blood is sensitive to blood oxygenation. In particular, it has been shown that (129)Xe T(1) is shorter in venous blood than in arterial blood. We have studied the T(1) of hyperpolarized (129)Xe dissolved in human blood as a function of blood oxygenation level, sO(2), in the physiological oxygenation range. We show that the (129)Xe relaxation rate, T(1)(-1), varies in a nonlinear fashion as a function of sO(2). This finding suggests that direct interaction of xenon with the paramagnetic heme group of deoxyhemoglobin is not the dominant oxygenation-dependent relaxation mechanism for (129)Xe in blood. These results corroborate the idea that the oxygenation-dependence of (129)Xe T(1) is determined by conformational changes of hemoglobin induced by oxygen binding.
血液中超极化（129）Xe的自旋-晶格弛豫时间T(1)对血液氧合敏感。特别是，研究表明静脉血中（129）Xe的T(1)比动脉血中的短。我们研究了溶解在人血中的超极化（129）Xe的T(1)在生理氧合范围内随血氧水平sO(2)的变化。我们发现（129）Xe弛豫率T(1)(-1)作为sO(2)的函数呈非线性变化。这一发现表明，氙与脱氧血红蛋白的顺磁性血红素基团的直接相互作用不是血液中（129）Xe依赖氧合的主要弛豫机制。这些结果证实了（129）Xe T(1)的氧合依赖性由氧结合诱导的血红蛋白构象变化决定这一观点。
