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Proglycogen and macroglycogen in equine skeletal muscle

response to exercise in standardbred trotters and in horses with polysaccharide storage myopathy

Bröjer, Johan (2006). Proglycogen and macroglycogen in equine skeletal muscle. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2006:41
ISBN 91-576-7090-0
[Doctoral thesis]

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The first aim of the present thesis was to establish a method for determination of proglycogen (PG) and macroglycogen (MG) in equine skeletal muscle. The measurement technique for determination of PG and MG was accurate and gave reproducible results. There was an excellent correlation for total glycogen determined in muscle biopsy specimens between the new PG and MG technique and the traditional acid hydrolysis method. A further aim was to examine the degradation of PG and MG in Standardbreds during a maximal exercise test. Horses performed an incremental maximal treadmill exercise test in one-minute steps until they no longer could keep pace with the treadmill. The exercise test induced an anaerobic metabolic response as demonstrated by decreased glycogen, ATP and creatine phosphate and increased lactate in muscle after exercise. The two fractions of glycogen contributed equally to glycogenolysis, 48% and 52% of total glycogen degradation for PG and MG respectively. A study was also performed to determine the degradation and resynthesis of PG and MG in skeletal muscle after intermittent exercise on a slope. At a training camp well trained Standardbreds performed a training session comprising a warm up period, seven repeated 500 m bouts of uphill exercise and a recovery period. Muscle biopsies were taken at rest, at the end of exercise and 1, 4, 8, 24, 48 and 78 hours post exercise. The exercise caused degradation in MG that was twice as large as for PG. The rate of glycogen resynthesis during 1 to 24 hours post exercise was higher for MG than PG. The rate of muscle glycogen synthesis thereafter was slower and did not differ between MG and PG up to 72 hours. The last study was conducted in order to determine PG, MG, glucose and glucose-6-phosphate (G-6-P) in skeletal muscle of horses with polysaccharide storage myopathy (PSSM) before and after light exercise. Horses with PSSM completed repeated intervals of 2 minutes of walking followed by 2 minutes of trotting until muscle cramping developed. Untrained control horses performed a similar exercise test for up to 20 minutes. Before exercise muscle glycogen concentrations were 1.5, 2.2 and 1.7 times higher for PG, MG and total glycogen respectively in PSSM horses compared to control horses. No changes in total glycogen, PG, MG, G-6-P and lactate were found after exercise. However, free glucose concentration increased in skeletal muscle in PSSM horses after exercise indicating that glucose uptake in skeletal muscle is augumented after light exercise.

Authors/Creators:Bröjer, Johan
Title:Proglycogen and macroglycogen in equine skeletal muscle
Subtitle:response to exercise in standardbred trotters and in horses with polysaccharide storage myopathy
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :May 2006
Number of Pages:51
ALLI. Bröjer, J.T., Stämpfli, H.R. and Graham, T.E. 2002. Effect of extraction time and acid concentration on the separation of proglycogen and macroglycogen in horse muscle samples. Canadian Journal of Veterinary Research 66, 201-206. II. Bröjer, J.T., Stämpfli, H.R. and Graham, T.E. 2002. Analysis of proglycogen and macroglycogen in muscle biopsy specimens obtained from horses. American Journal of Veterinary Research 63, 570 – 575. III. Bröjer, J., Jonasson, R., Schuback, K. and Essén-Gustavsson, B. 2002. Pro- and macroglycogenolysis in skeletal muscle during maximal treadmill exercise. Equine Veterinary Journal, Supplement 34, 205-208. IV. Bröjer, J., Holm, S., Jonasson, R., Hedenström, U. and Essén-Gustavsson, B. 2006. Synthesis of proglycogen and macroglycogen in skeletal muscle of Standardbred trotters after intermittent exercise. Submitted manuscript. V. Bröjer, J.T., Essén-Gustavsson, B., Annandale, E.J. and Valberg, S.J. 2006. Proglycogen, macroglycogen, glucose and glucose-6-phospate concentrations in skeletal muscles of horses with polysaccharide storage myopathy performing light exercise. American Journal of Veterinary Research. Provisionally accepted.
Place of Publication:Uppsala
ISBN for printed version:91-576-7090-0
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:horses, racehorses, glycogen, muscles, muscular diseases, metabolism, physical activity
Keywords:glycogen, proglycogen, macroglycogen, horse, muscle, metabolism, polysaccharide storage myopathy
Permanent URL:
ID Code:1109
Department:(VH) > Dept. of Clinical Sciences
Deposited By: Johan Bröjer
Deposited On:10 May 2006 00:00
Metadata Last Modified:02 Dec 2014 10:09

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