Degree of correspondence between contractile and oxidative capacities in horse muscle fibres: a histochemical study.

The study examines the relationship between contractile and oxidative capacities in horse muscle fibers, and suggests that oxidative capacity and contractile capacity should be categorized separately in muscle fiber classification.

Research Method

• The researchers performed a histochemical analysis on the muscle samples taken from the middle gluteal muscle of 95 untrained adult horses of varying ages and genders.
• This analysis utilized the myosin adenosine triphosphatase (m-ATPase) and nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR) staining techniques to evaluate fiber types and their oxidative capacities.
• Fiber types were classified into three categories based on m-ATPase activity after preincubation at pH 4.4. This resulted in the identification of type I, type IIA, and type IIB fibers.

Findings

• The team highlighted the percentage of Fast Twitch Glycolytic (FT) fibers and the proportion of type IIB fibers with both “high” and “low” oxidative capacity, as determined through analyzing serial sections stained for NADH-TR.
• There was a significantly higher proportion of type IIB fibers than FT fibers. However, both these fiber types were found to be correlated.
• About 72.2% of identified type IIB fibers showed a low oxidative capacity. The remaining 27.8% of these type IIB fibers, however, displayed a high aerobic potential.

Conclusion

• These results revealed that a muscle fiber’s contractile capacity didn’t determine its oxidative profile, challenging existing perceptions about the relationship between these two attributes.
• Therefore, the researchers suggested that muscle fibers should be classified solely on m-ATPase activity, as this property is related to the structure of contractile proteins present in these fibers.
• On the other hand, the oxidative capacity should be evaluated separately, and should not be considered as a classification criterion for muscle fibers in horses.