NADH VIDEOFLUORIMETRY TO MONITOR THE ENERGY-STATE OF SKELETAL-MUSCLE IN-VIVO

Background. Reduction of the cellular energy state during ischemia of the limbs is an important determinant for development of necrosis. Sin ce energy conversion in the mitochondria is based on electron transpor t from NADH to molecular O-2, the NADH/NAD(+) redox couple reflects th e mitochondrial redox state and cellular O-2 requirement. The applicab ility of NADH videofluorimetry to monitor noninvasively changes in the energy state of intact resting skeletal muscle as a function of oxyge nation was investigated in a rat model. Materials and methods. In mech anically ventilated rats (n = 6), NADH fluorescence images of the grac ilis muscle were recorded under different oxygenation conditions. Indu ction of anoxic and ischemic hypoxia were verified by simultaneous mea surement of tissue oxygen pressure and afferent blood flow. Results. A noxic hypoxia and ischemic hypoxia increased the NADH fluorescence int ensity by 46.0 +/- 15.0 and 30.8 +/- 26.4%, respectively. The response time of NADH fluorescence intensity, tissue oxygen pressure, and affe rent blood flow was similar during development of anoxic and ischemic hypoxia. Upon reperfusion and reoxygenation, however, NADH fluorescenc e intensity changed significantly earlier than tissue oxygen pressure as measured by an oxygen needle electrode. Conclusion. These results d emonstrate that changes in NADH fluorescence intensity reflect oxygena tion changes in intact skeletal muscle in vivo. Since NADH videofluori metry, in contrast to oxygen needle electrode measurements, noninvasiv ely visualizes temporal and regional changes in the energy state of sk eletal muscle, this technique has the potential to improve clinical ev aluation of ischemia/reperfusion injury and tissue viability. (C) 1998 Academic Press.