Physicochemical Characteristics of Rat Muscle Glycogen Fractions.

Introduction: Homogenization of animal tissues with cold Perchloric Acid (PCA) produces two fractions of glycogen, Acid Soluble Glycogen (ASG) and Acid Insoluble Glycogen (AIG).

Aim: To determine some physicochemical characteristics of muscle glycogen fractions in two groups of rat.

Materials And Methods: An experimental study was conducted on two groups of five male rats. Rats in control group were kept at rest and in case group on 30 minutes physical activity. The content of carbohydrate, protein, phosphate, index and relative Molecular Weights (MWs) were determined for glycogen fractions.

Results: Total glycogen decreased following muscular activity (1.40±0.08, mg/g wet muscle vs. 0.97±0.11, p<0.05) and the change occurred totally in ASG (1.02±0.07 vs. 0.57±0.07, p=0.017), whereas, AIG changed insignificantly (0.39±0.05 vs. 0.36±0.02, p=0.5). The protein content of AIG was about 5.5 times of ASG fraction. The ratio of carbohydrate to protein was 0.33±0.01 (mg/mg) in ASG and decreased to 0.19±0.02, p=0.01 after 30 minute activity. This ratio in AIG was about 6% of ASG fraction and did not change significantly during physical activity. The ratio of phosphate to protein was three times in ASG relative to AIG at rest and did not change following activity. The index of molecular weight was calculated for each fraction of glycogen as the ratio of concentration per osmolality (mg/mmol). The index was 1.82±0.02 for ASG at rest and decreased significantly to 1.07±0.12, p<0.05 following 30 minutes activity. The index did not change significantly for AIG fraction (0.56±0.05 vs. 0.48±0.10, p=0.4). The relative MW of the fractions of ASG to AIG was 3.3±0.3 at rest and decreased significantly to 2.2±0.6, p<0.05 following 30 minutes activity.

Conclusion: Two fractions of muscle glycogen, ASG and AIG, differ in the relative carbohydrate: protein content and ASG have a higher mean of MW and is more metabolic active form.