P2.26 Dynamic Assessment of Vascular Resistances in Diabetic Miceusing a Non-Invasive NMR Imaging Approach

Abstract

The dynamic determination of peripheral vascular resistances requires simultaneous determination of organ perfusion and systemic arterial blood pressure (BP). We developed an integrated Nuclear Magnetic Resonance (NMR) approach combining measurements of systolic and diastolic BP with tissue perfusion by NMR-Imaging using Arterial Spin Labeling technique (NMRI-ASL) in small animals. This allowed non-invasive determination of local peripheral resistances in vivo. As a first example of application, we assessed the vascular conductance in skeletal muscle of type-2 diabetic mice.

Experiments were performed on a Bruker 4T NMR system using a custom-developed setup adapted to small animal investigations.

Tissue perfusion quantification in gastrocnemius of mice was performed with a NMR sequence combining fast imaging with ASL¹. It uses magnetically-labeled blood water as an endogenous tracer to quantify perfusion.

NMR method to determine BP is based on the sphygmomanometric principle: the caudal artery of the mouse was subjected to an external pressure from a tail air cuff. Arterial inflow signal was collected by single-slice dynamic NMR angiography and analyzed by reference to air pressure in the tail cuff.

These hemodynamics parameters were measured during reactive hyperemia after arterial occlusion in 10-week-old male db/db diabetic mice (n=17) and controls (n=14).

Using our dynamic NMR approach, we found both decreases in mean BP (68±9 vs 91±15 mmHg; p<0.05) and maximal perfusion (82±19 vs 105±38 ml.min^-1.100g^-1 p<0.05) in young db/db mice. However, we found that their maximal vascular conductance was not altered (1.22±0.3 vs 1.27±0.7 ml.min^-1.100g^-1.mmHg^-1), hence the relevance of our integrated approach. 1-Raynaud MRM 2001