Effects of Hypothermia on Skeletal Muscle Contractile Function: Comparison between Hibernators and Non‐hibernators

• Published in: The FASEB Journal
• Main Authors: Krishnan, Jishnu K S, Hunstiger, Moriah, Rogers, Jace, Oliver, Scott Ryan
• Other Authors: University of Alaska Fairbanks, National Institute of General Medical Sciences
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2019
• Subjects: Arctic
• Online Access: http://dx.doi.org/10.1096/fasebj.2019.33.1_supplement.868.34

The primary function of skeletal muscle (SKM) is to implement locomotion, but muscles also serve other important functions such as generating heat through shivering (and non‐shivering), which involves continuous contraction and relaxation. Arctic ground squirrels (AGS), Spermophilus parryii, undergo extreme temperature fluctuations during the hibernating season (body temperature as low as −3 °C), where they mostly remain physically inactive. Despite prolonged periods of immobilization and starvation during hibernation, AGS and other hibernating mammals are protected from muscle atrophy, weakness, and loss of protein content. In contrast, non‐hibernators (like Sprague Dawley (SD)) are susceptible to muscle atrophy, rhabdomyolysis and myotonia etc. due to muscle inactivity. To our knowledge no study has shown the effects of temperature on muscle contractile function compared between hibernators and non‐hibernators. We hypothesized that hibernators maintain their muscle contractile function and performance, over a wider temperature range compared to non‐hibernators. We characterized and compared the alterations in SKM contractile function during hypothermic temperature stress. An Ex vivo functional assay was implemented, utilizing a tissue organ bath system (TOBS) and involved extracting diaphragm muscle from both AGS and SD, create strips made from SKM while keeping it in oxygenated Ringers solution. Following transfer of strips to respective organ bath chambers, muscles were exposed to 37°C for 30 mins (control/initial phase), 30 mins of experimental temperature (4 °C; 15 °C; 25 °C and 37 °C), and then finally back to 37 °C for 30min (recovery phase). Real time data (contractile function via force transducer) was recorded from the TOBS using LabChart Pro, and a force frequency curve was plotted. Preliminary data suggest that SKM of both hibernators and non‐hibernators during the experimental hypothermia phase showed suppressed (and slow) contractile function in both species, with the lowest force values at 4 °C. ...