[Effects of acute arterial occlusion on muscle energy metabolism. An experimental model using phosphorus NMR spectroscopy in the rat].

Phosphorus-31 MR spectroscopy allows non-invasive evaluation of the energy state of a tissue and was used to study effects of acute ischemia in rat skeletal muscle. Male Wistar rats were anesthetized with pentobarbital (50 mg.kg-1) and the femoral artery ligated on leaving the abdominal cavity. Animals were then set inside a superconducting magnet (Bruker 2.35 T) and a circular coil (15 mm diameter) placed on leg facing gastrocnemius muscle. Pulse lengths were chosen in such a may that the sensitive zone would include mainly gastrocnemius muscle. Signals were accumulated over 2 or 18 minutes. One hour after insertion of ligature muscular exercise was provoked over 20 minutes by electrical stimulation of sciatic nerve (4 Hz, 2 to 5 V). Muscles were removed at different stages of the test for biochemical assays. Figure 1 includes spectra at 2 and 18 minutes showing the effects of ischemic when compared with normoxic muscle exercise. Figure 2, showing phosphocreatine (PC) and ATP levels, illustrates the accentuation under the effect of ischemia of degradation in PC during muscular exercise and its subsequent slow reconstitution. Table I lists more precise MR data obtained during 18 minutes and compares them with biochemical findings. Ischemic exercise appears also to induce significant degradation of ATP, accumulation of inorganic phosphate (Pi) and phosphomonoesters (PME) as well as persistent intracellular acidosis (pH 6.5 as against 7.1).(ABSTRACT TRUNCATED AT 250 WORDS)