Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0623, USA.
J Appl Physiol (1985). 2010 Nov;109(5):1384-93. doi: 10.1152/japplphysiol.00660.2010. Epub 2010 Aug 19.
Phenol is a neurolytic agent used for management of spasticity in patients with either motoneuron lesions or stroke. In addition, compounds that enhance muscle contractility (i.e., polyphenols, etc.) may affect muscle function through the phenol group. However, the effects of phenol on muscle function are unknown, and it was, therefore, the purpose of the present investigation to examine the effects of phenol on tension development and Ca(2+) release in intact skeletal muscle fibers. Dissected intact muscle fibers from Xenopus laevis were electrically stimulated, and cytosolic Ca(2+) concentration (Ca(2+)) and tension development were recorded. During single twitches and unfused tetani, phenol significantly increased Ca(2+) and tension without affecting myofilament Ca(2+) sensitivity. To investigate the phenol effects on Ca(2+) channel/ryanodine receptors, single fibers were treated with different concentrations of caffeine in the presence and absence of phenol. Low concentrations of phenol significantly increased the caffeine sensitivity (P < 0.01) and reduced the caffeine concentrations necessary to produce nonstimulated contraction (contracture). However, at high phenol concentrations, caffeine did not increase tension or Ca(2+) release. These results suggest that phenol affects the ability of caffeine to release Ca(2+) through an effect on the ryanodine receptors, or on the sarcoplasmic reticulum Ca(2+) pump. During tetanic contractions inducing fatigue, phenol application decreased the time to fatigue. In summary, phenol increases intracellular [Ca(2+)] during twitch contractions in muscle fibers without altering myofilament Ca(2+) sensitivity and may be used as a new agent to study skeletal muscle Ca(2+) handling.
苯酚是一种神经溶解剂，用于治疗运动神经元损伤或中风患者的痉挛。此外，增强肌肉收缩力的化合物（如多酚等）可能通过苯酚基团影响肌肉功能。然而，苯酚对肌肉功能的影响尚不清楚，因此，本研究旨在研究苯酚对完整骨骼肌纤维张力发展和钙释放的影响。从非洲爪蟾分离出完整的肌肉纤维，用电刺激，记录胞浆钙浓度([Ca 2 + ] c )和张力发展。在单次抽搐和非融合四极抽搐期间，苯酚显著增加[Ca 2 + ] c 和张力，而不影响肌丝钙敏感性。为了研究苯酚对钙通道/兰尼碱受体的影响，在存在和不存在苯酚的情况下，用不同浓度的咖啡因处理单纤维。低浓度的苯酚显著增加了咖啡因的敏感性（P < 0.01），并降低了产生非刺激收缩（收缩）所需的咖啡因浓度。然而，在高苯酚浓度下，咖啡因不能增加张力或钙释放。这些结果表明，苯酚通过影响兰尼碱受体或肌浆网 Ca 2 + 泵来影响咖啡因释放 Ca 2 + 的能力。在导致疲劳的四极收缩期间，苯酚的应用减少了疲劳时间。总之，苯酚在肌肉纤维的抽搐收缩过程中增加细胞内[Ca 2 + ]，而不改变肌丝钙敏感性，可作为研究骨骼肌钙处理的新试剂。
