MEASUREMENT OF STRAIN EXERTED ON BLOOD-VESSEL WALLS BY DOUBLE-QUANTUM-FILTERED H-2 NMR

In this study H-2 double quantum-filtered (DQF) NMR spectroscopy of wa ter molecules inside the blood vessel wall was used to monitor structu ral changes after the application of strain. This method was applied t o a variety of bovine large blood vessels, including aorta, coronary a rtery, carotid artery, and vena cava. Inducing strain in coronary arte ries by inflating them by air or water revealed dramatic changes in th e H-2 DQF spectral lineshapes. Uniaxial extensions of longitudinal and circumferential strips led to distinct spectral responses for the dif ferent blood vessels, While the spectral lineshapes for the coronary a nd the carotid arteries were very sensitive to longitudinal strain, th ey were not affected by circumferential stretching, For the aorta ther e were no changes in the lineshape upon strain, For the vena cava a la rge effect of strain was found that was independent of the choice of e longation axis, The effect of elongation on the spectra was assigned t o the outer layer, the adventitia, whereas spectral lineshapes that or iginated from inner layers, media and intima, were almost insensitive to strain, Angular dependence experiments proved the presence of macro scopic order in the strained state superimposed on a broad distributio n of the local directors, Our results demonstrate the sensitivity of H -2 DQF NMR as a probe for dynamic processes occurring on the microscop ic scale in a molecular network.