Skeletal muscle regulatory volume response to recovery period affected by extracellular osmolarity change

Abstract

Mammalian skeletal muscle cells exhibit an initial volume reduction, followed by a regulatory volume increase (RVI) back to baseline status in response to increased extracellular osmolarity. However, the muscle cells may not always reach complete recovery back to starting volume. In the present study, the response of muscle fibres to increased extracellular osmolarity via sucrose, NaCl, and NaLac treatment were investigated to observe RVI. Additionally, a recovery stage was examined to assess fibre response after RVI occurrence, during a period where extracellular osmolarity was replaced with an isosmotic environment. Adult mouse peroneous muscle fibre width measurements were obtained every 5–10 seconds for 30min in response to increased extracellular osmolarity via sucrose, NaCl or NaLactate treatment. Immediately after this period, solution was 3x-rinsed and replaced with plating media. New baseline images were obtained and image collection repeated for 30 minutes. The muscle fibres in the isosmotic environment continued to exhibit an increase in volume throughout the 30min recovery period. Also, the magnitude of peak volume decrease in the preceding treatment period did not negatively impact the degree of recovery. Results suggest that skeletal muscle cells possess an active mechanism to regain volume back towards baseline status irrespective of compensatory changes in extracellular osmolarity. Supported by NSERC of Canada