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Analysis of proglycogen and macroglycogen content in muscle biopsy specimens obtained from horses

Johan T. BröjerDepartment of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada N1G 2W1.
Current address is Department of Large Animal Clinical Sciences, Faculty of Veterinary Medicine, Swedish University of Agriculture, Box 7018, 750 07 Uppsala, Sweden.

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 DVM, MSc
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Henry R. StämpfliDepartment of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada N1G 2W1.

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 DVM, Dr Vet Med;
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Terry E. GrahamHuman Biology and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1.

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 PhD

Abstract

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 biopsy specimens.

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 was evaluated.

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 deeper parts.

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)

Abstract

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 biopsy specimens.

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 was evaluated.

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 deeper parts.

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)