Degree of correspondence between contractile and oxidative capacities in horse muscle fibres: a histochemical study.
Samples taken from the middle gluteal muscle of 95 untrained adult horses of different ages and sex were subjected to histochemical analysis using the myosin adenosine triphosphatase (m-ATPase) and nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR) staining techniques. Fibres were classified into types I, IIA and IIB according to m-ATPase activity after preincubation at pH 4.4. The percentage of FT (Fast-Twitch Glycolytic) fibres and the proportion of IIB fibres with "high" and "low" oxidative capacity were determined in serial sections stained for NADH-TR. Statistical analysis revealed a significantly higher proportion of IIB fibres than FT fibres (P less than 0.001), though both percentages were correlated. Thus, 72.2 +/- 17.6% of type IIB fibres showed low oxidative capacity, but the remaining 27.8 +/- 17.6% showed high aerobic potential, and thus did not correspond to FT fibres. These results confirm that the contractile capacity of a muscle fibre does not determine its oxidative profile. The different types of muscle fibre should thus be classified solely according to m-ATPase activity, since this characteristic is related to the molecular structure of contractile proteins. Oxidative capacity should be assessed separately, and not be used as a criterion for fibre classification in horses.
López-Rivero
J L
JL
Department of Comparative Anatomy and Pathological Anatomy, Faculty of Veterinary Sciences, University of Córdoba, Spain.
Agüera
E
E
Rodríguez-Barbudo
M V
MV
Galisteo
A M
AM
Morales-López
J L
JL
D000818:Animals; D005260:Female; D006651:Histocytochemistry; D006736:Horses / Q000033:anatomy & histology / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009132:Muscles / Q000033:anatomy & histology / Q000502:physiology*; D009218:Myosins / Q000378:metabolism; D009246:NADH Tetrazolium Reductase / Q000378:metabolism; D010084:Oxidation-Reduction
D009246:NADH Tetrazolium Reductase; D009218:Myosins