Measuring perfusion and bioenergetics simultaneously in mouse skeletal muscle: a multiparametric functional‐NMR approach

A totally noninvasive set‐up was developed for comprehensive NMR evaluation of mouse skeletal muscle function in vivo . Dynamic pulsed arterial spin labeling‐NMRI perfusion and blood oxygenation level‐dependent (BOLD) signal measurements were interleaved with 31 P NMRS to measure both vascular response and oxidative capacities during stimulated exercise and subsequent recovery. Force output was recorded with a dedicated ergometer. Twelve exercise bouts were performed. The perfusion, BOLD signal, pH and force–time integral were obtained from mouse legs for each exercise. All reached a steady state after the second exercise, justifying the pointwise summation of the last 10 exercises to compensate for the limited 31 P signal. In this way, a high temporal resolution of 2.5 s was achieved to provide a time constant for phosphocreatine (PCr) recovery ( τ PCr ). The higher signal‐to‐noise ratio improved the precision of τ PCr measurement [coefficient of variation (CV) = 16.5% vs CV = 49.2% for a single exercise at a resolution of 30 s]. Inter‐animal summation confirmed that τ PCr was stable at steady state, but shorter (89.3 ± 8.6 s) than after the first exercise (148 s, p  < 0.05). This novel experimental approach provides an assessment of muscle vascular response simultaneously to energetic function in vivo . Its pertinence was illustrated by observing the establishment of a metabolic steady state. This comprehensive tool offers new perspectives for the study of muscle pathology in mice models. Copyright © 2010 John Wiley & Sons, Ltd.