P-2-08-03
COMPARISON OF ENERGY METABOLISM AND NEUROMUSCULAR TRANSMISSION BETWEEN HIGH- AND LOW-FREQUENCY FATIGUE OF RAT HINDLIMB MUSCLES
Shinjiro Takata, Takaaki Ikata, Hiroaki Takai, Yoshihiro Hayashi, Tetsuya Matsuura (The University of Tokushima, Tokushima, Japan)
We studied the difference of energy metabolism and neuromuscular transmission during high- and low-frequency fatigue of rat hindlimb muscle by 31 P-MRS and electromyogram. The sciatic nerve was stimulated electrically using low frequency stimulation at 30 Hz and high frequency stimulation at 100 Hz. In the 2 minutes of stimulation, the ratio of phosphocreatine to inorganic phosphate + sugar phosphate during stimulation at 30 Hz and stimulation at 100 Hz were 0.28±0.04 and 0.53±0.06, respectively. The intracellular pH during stimulation at 30 Hz and stimulation at 100 Hz was 6.27±0.02 and 6.75±0.03, respectively. Later, the ratio and intracellular pH during stimulation at 30 Hz remained lower than those during stimulation at 100 Hz. The M wave amplitude during stimulation at 30 Hz maintained higher values than that during stimulation at 100 Hz. The results show that stimulation at 100 Hz allows low energetic loss of muscle, high intracellular pH and great neuromuscular transmission failure compared with stimulation at 30 Hz.
P-2-08-04
Effect of weight-bearing on energy state and enzyme activity in rat hindlimb muscles during recovery from sciatic nerve injury
TETSUYA MATSUURA, TAKAAKI IKATA, SHINJIRO TAKATA, HIROAKI TAKAI (The University of Tokushima, Tokushima, Japan) TAKAYUKI SOGABE, and KEIKO KOGA (Otsuka Pharmaceutical Co., Ltd, Tokushima)
We studied the effect of weight-bearing on energy state and enzyme activity in rat hindlimb muscles recovering from sciatic nerve injury. The sciatic nerve of 38 male Sprague-Dawley rats (14 weeks old, 350〜380g) were exposed and compressed with a silicon tube. The tubes around the sciatic nerve were detached after 1 week of compression. The animals were divided into two groups: normal weight-bearing group (N group) and hindlimb suspension for 2weeks group (HS group). Energy state in hindlimb muscles was assessed by 31P-NMR during exercise induced by transcutaneous electric stimulation (frequency, 40Hz; voltage, 5V). The activities of creatine kinase (CK) of gastrocnemius, soleus, and plantaris were measured by the Wako diagnostics creatine phosphokinase kit and adenylate kinase (AK) assayed, by the method of Passonncau and Lowry. The energy state of N group muscles were higher than those of HS muscles during stimulation (p<0.05). In enzyme activity measured, CK and AK in the gastrocnemius muscle in HS group were 0.25±0.01 (nmoles NBT reduced/min・mg protein) and 402±22 (nmoles NADPH produced/min・mg protein) respectively, while CK and AK in N group were 0.63±0.04 and 350±4, respectively. These results showed that weight-bearing played an important role in the energy metabolism in skeletal muscle recovering from nerve injury.
