title: Metabolic response to maximal exercise of 800 and 2,000 m in the thoroughbred horse.
abstract: To define the metabolic response to maximal exercise in the thoroughbred horse under field conditions, muscle biopsies and venous blood samples were taken from five horses after a single 800-m gallop and from four horses after a single 2,000-m gallop. Muscle and blood samples were also collected during 60 min of recovery. After exercise muscle ATP contents were decreased by 30 +/- 7 (SD) and 47 +/- 3% after the 800- and 2,000-m gallops, respectively. As indicators of purine catabolism, ammonia and uric acid increased in plasma, the accumulation being greater after the 2,000-m gallop. Blood ammonia peaked immediately after exercise and uric acid after 40-60 min of recovery. Muscle glycogen utilization over the 800- and 2,000-m gallops averaged 2.68 +/- 0.90 and 1.06 +/- 0.12 mmol glucosyl units.kg dry muscle-1.s-1, respectively, and the total used amounted to 27.3 +/- 6.6 and 32.5 +/- 8.8% of the initial store. Muscle lactate accumulation averaged 123.5 +/- 49.7 and 167.3 +/- 20.7 mmol/kg dry muscle, respectively, and declined during recovery with half times of 22.9 +/- 4.2 and 18.9 +/- 6.6 min. Blood lactate peaked 5-10 min after exercise. Exercise resulted in only a small increase in muscle glycerol content, but this continued to rise during recovery reaching 9-12 mmol/kg dry muscle after 20 min. During this time the increase in muscle glycerol content exactly matched the decline in glycerol 3-phosphate.
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism; D000818:Animals; D004734:Energy Metabolism; D005260:Female; D005990:Glycerol / Q000378:metabolism; D005994:Glycerophosphates / Q000378:metabolism; D006736:Horses / Q000502:physiology*; D007773:Lactates / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000378:metabolism*; D009919:Orchiectomy; D005082:Physical Exertion
chemical_list: D000227:Adenine Nucleotides; D005994:Glycerophosphates; D007773:Lactates; D000641:Ammonia; C029620:alpha-glycerophosphoric acid; D005990:Glycerol