Biochemical aspects of exercise in the horse

Anderson, Marion G (1973) Biochemical aspects of exercise in the horse. PhD thesis, University of Glasgow.

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The present study was undertaken to obtain information on some of the biochemical changes which take place in the horse during exercise and training. Of particular interest were changes in the serum levels of certain enzymes, the tissue (or tissues) of origin of these enzymes and the manner in which exercise resulted in their release into the circulation. In conjunction with these studies, the effects of exercise on various blood metabolites were investigated to determine the relative importance of carbohydrate and lipid in the energy metabolism of the exercising horse. Since the optimal conditions for assaying enzyme activity vary with the source of the enzyme, the optimal assay conditions for horse serum GOT, LDH, ALD and CK were first determined. Using this information, the effects of controlled exercise on serum concentrations of these enzymes were studied. Serum levels of LDH, ALD and CK were found to Increase following exercise and the magnitude of these increases could be correlated with the duration of the exercise and the state of training of the animal. By comparing tissue LDH and CK isoenzyme patterns with serum isoenzyme patterns before and after exercise, the tissue of origin of these enzyme increases was found to be skeletal muscle (with some possible contribution from liver). An alteration in muscle cell membrane permeability which allows leakage of intracellular enzymes into the circulation was postulated. Monitoring of blood levels of glucose, lactate, pyruvate, free fatty acids and glycerol before, during and after exercise indicated that both carbohydrate and lipid catabolism were increased in the horse during exercise of varying degrees. Galloping (at 11.0-13.3 metres/sec) was found to involve anaerobic metabolism to a large extent while cantering (at 5.2-6.7 metres/sec) could be maintained by aerobic metabolism alone. Training was found to increase the animal's capacity for aerobic metabolism. Since the nature of the stimulus which causes changes in cell membrane permeability is still obscure, the possible involvement of catecholamines secreted during exercise was investigated. Although administration of adrenaline to resting horses resulted in increased serum enzyme levels, several features of this response were incompatible with the hypothesis that catecholamine secretion might be the only stimulus for enzyme release during exercise. Tissue hypoxia and lactate accumulation were discounted as possible stimuli since enzyme leakage occurred in the absence of detectable oxygen deficiency as indicated by lactate production. Several other aspects of the membrane permeability change were discussed.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: William L Weipers
Keywords: Veterinary science
Date of Award: 1973
Depositing User: Enlighten Team
Unique ID: glathesis:1973-73216
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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