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- Title
The availability of water associated with glycogen during dehydration: a reservoir or raindrop?
- Authors
King, Roderick F G J; Jones, Ben; O'Hara, John P
- Abstract
<bold>Purpose: </bold>This study evaluated whether glycogen-associated water is a protected entity not subject to normal osmotic homeostasis. An investigation into practical and theoretical aspects of the functionality of this water as a determinant of osmolality, dehydration, and glycogen concentration was undertaken.<bold>Methods: </bold>In vitro experiments were conducted to determine the intrinsic osmolality of glycogen-potassium phosphate mixtures as would be found intra-cellularly at glycogen concentrations of 2% for muscle and 5 and 10% for liver. Protected water would not be available to ionic and osmotic considerations, whereas free water would obey normal osmotic constraints. In addition, the impact of 2 L of sweat loss in situations of muscle glycogen repletion and depletion was computed to establish whether water associated with glycogen is of practical benefit (e.g., to increase "available total body water").<bold>Results: </bold>The osmolality of glycogen-potassium phosphate mixtures is predictable at 2% glycogen concentration (predicted 267, measured 265.0 ± 4.7 mOsmol kg-1) indicating that glycogen-associated water is completely available to all ions and is likely part of the greater osmotic system of the body. At higher glycogen concentrations (5 and 10%), there was a small amount of glycogen water (~ 10-20%) that could be considered protected. However, the majority of the glycogen-associated water behaved to normal osmotic considerations. The theoretical exercise of selective dehydration (2 L) indicated a marginal advantage to components of total body water such as plasma volume (1.57% or 55 mL) when starting exercise glycogen replete.<bold>Conclusion: </bold>Glycogen-associated water does not appear to be a separate reservoir and is not able to uniquely replete water loss during dehydration.
- Subjects
PHOSPHATE metabolism; ANIMAL experimentation; BIOLOGICAL models; CATTLE; DEHYDRATION; GLYCOGEN; LIVER; POTASSIUM compounds; WATER in the body; OSMOLAR concentration; SKELETAL muscle
- Publication
European Journal of Applied Physiology, 2017, Vol 117, Issue 12, pN.PAG
- ISSN
1439-6319
- Publication type
journal article
- DOI
10.1007/s00421-017-3768-9