Objective—To determine proglycogen (PG) and
macroglycogen (MG) content in equine skeletal muscle
and to compare 2 analytical methods (acid hydrolysis
[AC] and PG plus MG determination) for measurement
of total muscle glycogen content (Glytot) in
Sample Population—Muscle biopsy specimens
obtained from 41 clinically normal horses.
Procedure—Forty-five muscle biopsy specimens
obtained from the middle gluteal (n = 31) or triceps
(14) muscle were analyzed, using AC and MG plus
PG determination for Glytot. Variability within muscle
biopsy specimens for each method was calculated
from duplicate analyses of muscle specimens.
In a second experiment, variation in MG and
PG content between muscle biopsy specimens and
the effect of sample collection depth on the concentration
of MG and PG in the middle gluteal muscle
Results—There was a strong correlation ( r = 0.99)
between Glytot values obtained by use of AC and MG
plus PG determination. Coefficients of variation for
within- and between-specimen variability of Glytot
were approximately 4% for each method. The PG
fraction was always in excess of the MG fraction.
Biopsy specimens obtained from the superficial part
of the middle gluteal muscle contained significantly
more Glytot and PG than specimens obtained from
Conclusions and Clinical Relevance—This study
confirms that MG and PG exist in equine skeletal
muscle and can be measured reliably in biopsy samples.
This technique could be applied in future studies
to investigate glycogen metabolism in exercising
horses and horses with glycogen-storage diseases.
(Am J Vet Res 2002;63:570–575)