Effects of The Dehydration on The Characteristics of Water Molecule in The Skeletal Muscles During Under Running Exercise High-temperature Environment

Abstract

It is known that the dehydration is a major factor of onset of the heat stroke during sports activity under high-temperature environment. However, the relationship between the dehydration and the profiles of water molecule within the skeletal muscles are poorly understood during sports activity under high-temperature. The present study examined the effects of the dehydration on the characteristics of water molecule and its related factors in the skeletal muscles during running exercise under high-temperature. In slow muscles, in running group, both the muscle water content and free water content were significantly lower than that in control group, respectively (p<0.05)．On the other hand, in fast muscles, there were no significant differences in these factors between both groups. Neither expression levels of AQP4 nor AQP1, that were the selective water channel, were changed in the skeletal muscles during running exercise under high-temperature. Likewise, the changes of the expression levels of α2 Na,K-ATPase, which was related to osmoregulation, were induced in skeletal muscles by running exercise under high-temperature. In conclusion, the present study indicated that the prime mover, i.e. slow muscles but not fast muscles, were induced significant loss of water, particularly free water, due to the dehydration during running exercise under high-temperature. On the other hand, it was suggested that the dehydration during running exercise under high-temperature may not participate in the regulation of the selective water channel AQP4 and AQP1 expression in both fast and slow muscles. Furthermore, it was suggested that the dehydration during running exercise under high-temperature may directly not induce the change of the intracellular osmotic pressure due to the change ofα2 Na,K-ATPase expression levels. These findings indicated in the present study may be useful to understand the molecular properties of skeletal muscles in the heat stroke during sports activity under high-temperature environment.