Meyer R A, Prior B M, Siles R I, Wiseman R W
Molecular Imaging Research Center, Departments of Physiology and Radiology, Michigan State University, East Lansing, MI 48824, USA.
NMR Biomed. 2001 May;14(3):199-203. doi: 10.1002/nbm.702.
Previous studies suggest that the activity-induced increase in (1)H-NMR transverse relaxation time (T(2)) observed in mammalian skeletal muscles is related to an osmotic effect of intracellular metabolite accumulation. This hypothesis was tested by comparing T(2) (measured by (1)H-NMR imaging at 4.7 T) and metabolite changes (measured by (31)P-NMR spectroscopy) after stimulation in the muscles of a freshwater (crayfish, Orconectes virilis) vs two osmoconforming marine invertebrates (lobster, Homarus americanus; scallop, Argopecten concentricus). Intracellular pH significantly decreased after stimulation in the lobster tail muscle, but not in the crayfish tail or scallop phasic adductor muscles. The decrease in phosphoarginine-to-ATP ratio after stimulation was similar in the three muscles. Muscle T(2) increased from 37 to 43 ms (p < 0.02, n = 7) after stimulation in crayfish, but was unchanged in lobster muscle (32 ms, n = 7), and significantly decreased (from 40 to 36 ms, p < 0.02, n = 11) in scallop muscle. The observation that T(2) does not increase after stimulation in muscles of marine invertebrates with high natural osmolarity is consistent with the hypothesis that the T(2) increase in mammalian muscle is related to osmotically driven shifts of fluid between subcellular compartments.
先前的研究表明，在哺乳动物骨骼肌中观察到的活动诱导的（1）H-NMR横向弛豫时间（T（2））增加与细胞内代谢物积累的渗透效应有关。通过比较淡水生物（小龙虾，奥氏原螯虾）与两种渗透压顺应性海洋无脊椎动物（龙虾，美洲螯龙虾；扇贝，同心海湾扇贝）肌肉在刺激后的T（2）（通过4.7T的（1）H-NMR成像测量）和代谢物变化（通过（31）P-NMR光谱测量）来检验这一假设。刺激后，龙虾尾肌细胞内pH值显著降低，但小龙虾尾肌或扇贝相位性内收肌细胞内pH值未降低。三种肌肉在刺激后磷酸精氨酸与ATP比值的降低相似。小龙虾肌肉在刺激后T（2）从37毫秒增加到43毫秒（p < 0.02，n = 7），但龙虾肌肉（32毫秒，n = 7）无变化，扇贝肌肉则显著降低（从40毫秒降至36毫秒，p < 0.02，n = 11）。在具有高自然渗透压的海洋无脊椎动物肌肉中，刺激后T（2）不增加这一观察结果与哺乳动物肌肉中T（2）增加与亚细胞隔室之间流体的渗透驱动转移有关的假设一致。
