Structural and oxidative enzyme characteristics of the diaphragm.
Abstract: During exercise, the horse can achieve oxygen uptakes and ventilations in excess of 200 ml/kg/min and 1800 l/min, respectively. Whether the diaphragm has the capacity to contribute substantially to inspiratory effort in the exercising horse is not known. To investigate the potential for the horse diaphragm to generate tension, lung displacement and sustain ventilatory function, we measured diaphragm thickness, muscle length and oxidative enzyme activity (citrate synthase) within the ventral, medial and dorsal costal and crural diaphragm. In the diaphragms of 6 mature horses (5 Thoroughbreds, one Quarter Horse; body mass (mean +/- s.e.) 475 +/- 14 kg, age 4 +/- 1 years), the mass of the freshly-excised diaphragm was 4.54 +/- 0.19 kg of which 79% was the costal diaphragm, 17% the crural diaphragm and 4% the central tendon. The medial costal region (2.1 +/- 0.1 cm) was significantly thicker (P3.2 +/- 0.3 cm, P<0.05) than any costal diaphragm region. With respect to the costal diaphragm, excised muscle length was greatest (P<0.05) in the medial costal (17.2 +/- 1.0 cm) than either the ventral costal (<12.6 +/- 1.5 cm) or dorsal costal (<13.9 +/- 1.8 cm) regions and therefore the medial region would be expected to exhibit the greatest absolute length change on inspiration. Citrate synthase activity was high throughout the diaphragm (40.8 +/- 113 to 55.3 +/- 9.7 micromol/g/min), but was not significantly different among regions. These structural characteristics and the oxidative potential of the horse diaphragm are consistent with the diaphragm providing a significant and substantial contribution to the inspiratory effort during exercise in the horse. Consequently, clinical and physiological investigations of exercise performance should not ignore the potentially crucial importance of the diaphragm.
Publication Date: 2002-10-31 PubMed ID: 12405734DOI: 10.1111/j.2042-3306.2002.tb05466.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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This research investigates the role and structural characteristics of the diaphragm in horses during exercise. The findings suggest that the diaphragm, particularly its medial region, may significantly contribute to the respiratory function during exercise.
Introduction and Objective
- When horses exercise, they are capable of achieving high levels of oxygen uptake and ventilation. The role of the horse’s diaphragm in this respiratory function was largely unexplored at the time of this study.
- The researchers aimed to explore the potential of the horse’s diaphragm to generate tension, displace the lung and maintain respiratory function during exercise.
- To achieve this, they examined the thickness, length, and oxidative enzyme activity (specifically, citrate synthase activity) in different regions of the diaphragm.
Methodology
- The study utilized six mature horses as subjects. After the horses’ diaphragms were excised, measurements were taken of their weight, muscle length, thickness, and citrate synthase activity.
- The measurements covered the ventral, medial, and dorsal costal, and the crural sections of the diaphragm, as well as the central tendon.
Key Findings
- Most of the diaphragm’s weight was attributed to the costal diaphragm, with minor portions accounted for by the crural diaphragm and the central tendon.
- The thickness of the diaphragm varied by region: it was found to be thickest in the medial costal region, which was significantly greater than the ventral and dorsal costal regions, and the crural diaphragm had a greater thickness than any of the costal diaphragm regions.
- The length of the excised muscle was largest in the medial costal region, therefore, it has the potential for the greatest length change during inspiration.
- Citrate synthase activity, indicative of the diaphragm’s oxidative capacity, was uniformly high across all diaphragm regions. No statistically significant differences were observed between the regions.
Conclusion
- The structural characteristics and high oxidative potential of the horse’s diaphragm, especially the medial aspects, suggest that it plays a significant role in respiratory function during exercise.
- The study emphasizes the importance of taking the diaphragm into account when conducting clinical and physiological studies on exercise performance in horses.
Cite This Article
APA
Poole DC, Petrisko RN, Anderson L, Fedde MR, Erickson HH.
(2002).
Structural and oxidative enzyme characteristics of the diaphragm.
Equine Vet J Suppl(34), 459-463.
https://doi.org/10.1111/j.2042-3306.2002.tb05466.x Publication
Researcher Affiliations
- Department of Kinesiology, Kansas State University, Manhattan 66506-5802, USA.
MeSH Terms
- Animals
- Body Weight
- Citrate (si)-Synthase / metabolism
- Diaphragm / anatomy & histology
- Diaphragm / enzymology
- Diaphragm / physiology
- Functional Residual Capacity
- Horses / anatomy & histology
- Horses / physiology
- Physical Conditioning, Animal / physiology
- Respiratory Mechanics / physiology
- Total Lung Capacity
Grant Funding
- HL-17731 / NHLBI NIH HHS
- HL-50306 / NHLBI NIH HHS
Citations
This article has been cited 2 times.- Fitzharris LE, Hezzell MJ, McConnell AK, Allen KJ. Training the equine respiratory muscles: Ultrasonographic measurement of muscle size. Equine Vet J 2023 Mar;55(2):295-305.
- Fogarty MJ, Sieck GC. Evolution and Functional Differentiation of the Diaphragm Muscle of Mammals. Compr Physiol 2019 Mar 14;9(2):715-766.
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