Non-invasive and quantitative evaluation of peripheral vascular resistances in rats by combined NMR measurements of perfusion and blood pressure using ASL and dynamic angiography

Abstract

The in vivo determination of peripheral vascular resistances (VR) is crucial for the assessment of arteriolar function. It requires simultaneous determination of organ perfusion (F) and arterial blood pressure (BP). A fully non-invasive method was developed to measure systolic and diastolic BP in the caudal artery of rats based on dynamic NMR angiography. A good agreement was found between the NMR approach and the gold standard techniques (linear regression slope = 0.98, R2 = 0.96). This method and the ASL-MRI measurement of skeletal muscle perfusion were combined into one single NMR experiment to quantitatively evaluate the local vascular resistances in the calf muscle of anaesthetized rats, in vivo and non-invasively 1) at rest: VR = 7.0 ± 1.0mmHg·min 100 g·ml-1, F = 13 ± 3ml min-1.100 g-1 and mean BP (MBP) = 88 ± 10 mmHg; 2) under vasodilator challenge (milrinone): VR = 3.7 ± 1.1mmHgmin.100 gml-1, F = 21 ± 4ml min-1.100 g-1 and MBP = 75 ± 14 mmHg; 3) under vasopressor challenge (norepinephrine): VR = 9.8 ± 1.2mmHgmin 100 gml-1, F = 14 ± 3ml min -1.100 g-1 and MBP = 137 ± 2mmHg. Copyright © 2009 John Wiley & Sons, Ltd.