Document Detail

Structural and oxidative enzyme characteristics of the diaphragm.
MedLine Citation:
PMID:  12405734     Owner:  NLM     Status:  MEDLINE    
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 (P<0.05) than either the ventral (1.4 +/- 0.1 cm) or dorsal (1.2 +/- 0.2 cm) costal regions and the crural diaphragm was significantly thicker (>3.2 +/- 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.
D C Poole; R N Petrisko; L Anderson; M R Fedde; H H Erickson
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Equine veterinary journal. Supplement     Volume:  -     ISSN:  -     ISO Abbreviation:  Equine Vet J Suppl     Publication Date:  2002 Sep 
Date Detail:
Created Date:  2002-10-30     Completed Date:  2003-02-26     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9614088     Medline TA:  Equine Vet J Suppl     Country:  England    
Other Details:
Languages:  eng     Pagination:  459-63     Citation Subset:  IM    
Department of Kinesiology, Kansas State University, Manhattan 66506-5802, USA.
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MeSH Terms
Body Weight
Citrate (si)-Synthase / metabolism*
Diaphragm / anatomy & histology*,  enzymology*,  physiology
Functional Residual Capacity
Horses / anatomy & histology,  physiology*
Physical Conditioning, Animal / physiology*
Respiratory Mechanics / physiology*
Total Lung Capacity
Grant Support
Reg. No./Substance:
EC (si)-Synthase

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