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Skeletal Muscle and Hepatic Glycogen Content in Birds
Author(s) -
Ferguson Donna,
Braun Eldon J.
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.1055.14
Subject(s) - glycogen , medicine , glycogenolysis , endocrinology , skeletal muscle , glut4 , insulin , glycogenesis , glycogen synthase , carbohydrate metabolism , chemistry , glucose uptake , metabolism , biology
Plasma glucose levels (Pglu) in birds are relatively elevated (10–15 mM/L) compared to mammals of similar body mass (5 mM/L). In mammals, insulin stimulated glucose uptake into myocytes via GLUT4, and diffusive glucose uptake into hepatocytes via GLUT2 removes glucose from circulation to maintain a consistent Pglu and the glucose can be subsequently converted to glycogen for storage. In birds, there is evidence that GLUT4 is absent from myocytes (Sweazea and Braun, 2005), which would potentially limit the amount of glucose available to skeletal muscle tissue for metabolism and glycogen storage. In our study, we attempt to quantify the glycogen content in liver and muscle tissue of birds with rat tissue as a control. Using a phenol‐sulfuric acid assay (Siu Lo, et al, 1970), we are able to measure the amount of glycogen stored by hydrolyzing the glycogen to glucose monomers and use colorimetric spectroscopy to measure absorbance versus micrograms of glycogen. Preliminary data show that although fasted and fed rats have a large deviation in hepatic glycogen stores, bird hepatic glycogen stores are relatively stable, suggesting that glycogenolysis is not a primary metabolic process. The lower glycogen stores in bird skeletal muscle also suggests a lack of insulin stimulated, post‐prandial glucose uptake into muscle and therefore a limited use of this substrate for metabolism, despite the markedly elevated Pglu.