Adaptation of rat skeletal muscle to creatine depletion: AMP deaminase and AMP deamination.
Adaptation of rat skeletal muscle to creatine depletion: AMP deaminase and AMP deamination.
复制标题
大鼠骨骼肌对肌酸消耗的适应：AMP 脱氨酶和 AMP 脱氨。
DOI：
10.1152/jappl.1992.73.6.2713
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Holloszy,JO
中科院分区：
文献类型：
--
作者：
Ren,JM;Holloszy,JO
AMP脱氨酶催化收缩肌肉中形成的AMP脱氨为肌苷5‘-单磷酸(IMP)。慢抽动肌的AMP脱氨酶活性仅为快抽动肌的约30%，而在剧烈收缩活动中，慢抽动肌的肌内膜蛋白生成率要低得多。我们发现，给大鼠喂食肌酸类似物β-鸟嘌呤丙酸(β-GPA)，导致肌酸耗竭，导致肌肉AMP脱氨酶大幅下降。这种适应性被用来评估AMP脱氨酶活性水平在解释慢抽动和快抽动肌肉中IMP产生的差异中所起的作用。摄食3wk的β-GPA可使快抽动比目鱼肌的AMP脱氨酶活性降至与正常慢抽动比目鱼肌相似的水平，但对剧烈收缩时IMP升高的幅度无影响。尽管喂食β-GPA的大鼠的正常比目鱼肌和外周棘肌中的ATP也有类似的下降，但对强烈收缩活动的反应，比目鱼肌中IMP的增加只有大约30%。这些结果表明，在收缩活动过程中，慢抽动骨骼肌较快抽动骨骼肌积累较少的IMP不是由于慢抽动肌中AMP脱氨酶水平较低所致。
AMP deaminase catalyzes deamination of the AMP formed in contracting muscles to inosine 5′-monophosphate (IMP). Slow-twitch muscle has only approximately 30% as high a level of AMP deaminase activity as fast-twitch muscle in the rat, and rates of IMP formation during intense contractile activity are much lower in slow-twitch muscle. We found that feeding the creatine analogue beta-guanidinopropionic acid (beta-GPA) to rats, which results in creatine depletion, causes a large decrease in muscle AMP deaminase. This adaptation was used to evaluate the role of AMP deaminase activity level in accounting for differences in IMP production in slow-twitch and fast-twitch muscles. beta-GPA feeding for 3 wk lowered AMP deaminase activity in fast-twitch epitrochlearis muscle to a level similar to that found in the normal slow-twitch soleus muscle but had no effect on the magnitude of the increase in IMP in response to intense contractile activity. Despite a similar decrease in ATP in the normal soleus and the epitrochlearis from beta-GPA-fed rats, the increase in IMP was only approximately 30% as great in the soleus in response to intense contractile activity. These results demonstrate that the accumulation of less IMP in slow- compared with fast-twitch skeletal muscle during contractile activity is not due to the lower level of AMP deaminase in slow-twitch muscle.