Laitano Orlando, Sheikh Laila H, Mattingly Alex J, Murray Kevin O, Ferreira Leonardo F, Clanton Thomas L
Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, United States.
Colegiado de Educação Física, Federal University of Vale do São Francisco, Petrolina, Brazil.
Front Physiol. 2018 Oct 31;9:1496. doi: 10.3389/fphys.2018.01496. eCollection 2018.
Hyperthermia and dehydration can occur during exercise in hot environments. Nevertheless, whether elevations in extracellular osmolality contributes to the increased skeletal muscle tension, sarcolemmal injury, and oxidative stress reported in warm climates remains unknown. We simulated osmotic and heat stress, , in mouse limb muscles with different fiber compositions. Extensor digitorum longus (EDL) and soleus (SOL) were dissected from 36 male C57BL6J and mounted at optimal length in tissue baths containing oxygenated buffer. Muscles were stimulated with non-fatiguing twitches for 30 min. Four experimental conditions were tested: isotonic-normothermia (285 mOsm•kg and 35°C), hypertonic-normothermia (300 mOsm•kg and 35°C), isotonic-hyperthermia (285 mOsm•kg and 41°C), and hypertonic-hyperthermia (300 mOsm•kg and 41°C). Passive tension was recorded continuously. The integrity of the sarcolemma was determined using a cell-impermeable fluorescent dye and immunoblots were used for detection of protein carbonyls. In EDL muscles, isotonic and hypertonic-hyperthermia increased resting tension ( < 0.001). Whereas isotonic-hyperthermia increased sarcolemmal injury in EDL ( < 0.001), this effect was absent in hypertonic-hyperthermia. Similarly, isotonic-hyperthermia elevated protein carbonyls = 0.018), a response not observed with hypertonic-hyperthermia. In SOL muscles, isotonic-hyperthermia also increases resting tension ( < 0.001); however, these effects were eliminated in hypertonic-hyperthermia. Unlike EDL, there were no effects of hyperthermia and/or hyperosmolality on sarcolemmal injury or protein carbonyls. Osmolality selectively modifies skeletal muscle response to hyperthermia in this model. Fast-glycolytic muscle appears particularly vulnerable to isotonic-hyperthermia, resulting in elevated muscle tension, sarcolemmal injury and protein oxidation; whereas slow-oxidative muscle exhibits increased tension but no injury or protein oxidation under the conditions and duration tested.
在炎热环境中运动时可能会出现体温过高和脱水的情况。然而，细胞外渗透压升高是否会导致在温暖气候下所报道的骨骼肌张力增加、肌膜损伤以及氧化应激，目前仍不清楚。我们在具有不同纤维组成的小鼠肢体肌肉中模拟了渗透压和热应激。从36只雄性C57BL6J小鼠身上分离出趾长伸肌（EDL）和比目鱼肌（SOL），并将其以最佳长度安装在含有含氧缓冲液的组织浴中。用非疲劳性抽搐刺激肌肉30分钟。测试了四种实验条件：等渗 - 正常体温（285 mOsm•kg和35°C）、高渗 - 正常体温（300 mOsm•kg和35°C）、等渗 - 高温（285 mOsm•kg和41°C）以及高渗 - 高温（300 mOsm•kg和41°C）。持续记录被动张力。使用一种细胞不可渗透的荧光染料来确定肌膜的完整性，并使用免疫印迹法检测蛋白质羰基。在EDL肌肉中，等渗和高渗 - 高温会增加静息张力（P < 0.001）。虽然等渗 - 高温会增加EDL中的肌膜损伤（P < 0.001），但在高渗 - 高温中不存在这种效应。同样，等渗 - 高温会使蛋白质羰基升高（P = 0.018），而高渗 - 高温未观察到这种反应。在SOL肌肉中，等渗 - 高温也会增加静息张力（P < 0.
