Linkage between whole body suspension-induced muscle a trophy and muscle proteolysis in rats

本研究旨在观察全身悬吊对大鼠骨骼肌溶酶体组织蛋白酶B和J活性及肌二肽（鹅肌肽和肌肽）含量的影响。6周龄雄性Sprague道利大鼠分为对照组（CON）和全身悬吊组（WBS）。WBS组大鼠在全身悬吊状态下维持10天。在实验当天早晨，分离慢缩肌（比目鱼肌：SOL）和快缩肌（腓肠肌：GAS）并称重。还立即取出肾上腺、脾脏和胸腺并称重。用荧光法测定肌肉溶酶体组织蛋白酶B和J的活性，用高效液相色谱法测定肌肉中鹅肌肽和肌肽的含量。WBS组SOL肌相对重量比CON组低0.67倍（p<0.001），而GAS肌相对重量无明显变化。SOL肌中溶酶体组织蛋白酶B和J活性分别为对照组的2.3倍和2.2倍，WBS组显著高于对照组。然而，这些溶酶体酶活性在GAS肌肉，没有改变的WBS。SOL肌中肌肽和鹅肌肽含量分别为对照组的0.56倍和0.78倍，WBS组显著低于对照组。而WBS对GAS肌中上述二肽含量无明显影响。这些结果表明，全身悬吊诱导的大鼠SOL肌萎缩可能与慢缩肌中较高的水解酶活性有关。

The purpose of this study is to examine the effect of whole body suspension on skeletal muscle lysosomal cathepsin B and J activities and muscle dipeptide (anserine and carnosine) contents in rats. Six week male Sprague Dawley rats were divided into the control (CON) group and whole body suspended (WBS) group. The rats of the WBS group were maintained under whole body suspension for 10 days. On the morning of the experimental day, slow-twitch muscle (soleus : SOL) and fast-twitch muscle (gastrocnemius : GAS) were isolated and weighed. Adrenal glands, spleen and thymus also were immediately removed and weighed. Muscle lysosomal cathepsin B and J activities were assayed by fluorimetry, and muscle anserine and carnosine contents were analyzed by HPLC method. The relative weight of SOL muscles was 0.67 times (p<0.001) lower in the WBS group than in the CON group, and that of GAS muscle was not changed by WBS. Lysosomal cathepsin B and J activities in SOL muscles were 2.3 times and 2,2 times, respectively, significantly higher in the WBS group than in the CON group. These lysosomal enzyme activities in GAS muscles, however, were not changed by WBS. Carnosine and anserine contents in SOL muscles were 0.56 times and 0.78 times, respectively, significantly lower in the WBS group than in the CON group. However, these dipeptide contents in GAS muscles were not changed by WBS. These results suggest that whole body suspension-induced SOL muscle atrophy in rats may be associated with higher hydrolytic enzyme activity in slow-twitch muscles.