Exercise-induced changes in the lung of Shetland ponies: ultrastructure and morphometry.
Abstract: The ultrastructural changes in pulmonary alveoli produced by running two ponies on a high speed treadmill at 7.6 m/sec, 3-degree incline, for 2 min support the hypothesis of pulmonary capillary stress failure as an explanation for exercise-induced pulmonary hemorrhage (EIPH). Light microscopy combined with scanning and transmission electron microscopy confirmed the presence of red blood cells and proteinaceous material in the alveolar lumina and interstitial swelling in approximately one third of the pulmonary alveoli examined. Morphometric analysis revealed that the blood-gas barrier was 30-77% thicker on the thin respiratory surface of the interalveolar septa in the cranial lobe of the two exercised ponies, i.e., 0.62 and 0.46 micron, compared to that of the unexercised control pony (0.35 micron). No change in blood-gas barrier thickness was observed in the caudal lobe, although that is where EIPH lesions have been observed in race-horses. Vascular pressures were low (20 mm Hg) in the pulmonary circulation of the Shetland pony at rest but increased more than three fold to 63 mm Hg during exercise. These preliminary morphological and physiological results indicate that a short burst of near-maximal exercise in a non-athletic equine can lead to structural changes in the blood-gas barrier and leakage of blood from pulmonary capillaries despite pulmonary vascular pressures being significantly lower than previously found in the racehorse.
Publication Date: 1997-01-01 PubMed ID: 9066143
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research study examines the ultrastructural changes in the lungs of ponies induced by intense exercise, suggesting that these changes may support the theory of capillary stress failure as the cause for Exercise-Induced Pulmonary Hemorrhage (EIPH) in horses.
Research Method
- The two Shetland ponies used for the study were made to run on a high-speed treadmill (7.6 m/sec with a 3-degree incline) for a period of two minutes.
- Pulmonary alveoli from the ponies were then examined using light, scanning and transmission electron microscopy to observe any changes caused by the burst of exercise.
Findings
- The exercise brought about significant structural changes in the ponies’ pulmonary alveoli. Of these, red blood cells and protein-rich material were found in the alveolar lumina (the space within the alveolus where gas exchange takes place). Swollen tissue was noticed in about a third of the pulmonary alveoli that were examined.
- Blood-gas barrier (the layer which allows for gas exchange between the air in the alveoli and the blood in the capillaries) was observed to thicken by 30-77% in the thin respiratory part of the walls separating two alveoli (interalveolar septa) in the lungs’ front-lobe (cranial lobe) compared to an unexercised control pony. The cranial lobe’s blood-gas barrier thickness rose to 0.62 and 0.46 microns from its original 0.35 microns.
- Interestingly, no change in blood-gas barrier thickness was observed in the back-lobe (caudal lobe) of the ponies despite EIPH lesions usually being observed in this area in race horses.
Conclusion
- Vascular pressures in a Shetland pony at rest were found to be low (20 mm Hg). This rose more than three times to 63 mm Hg during exercise.
- The researchers concluded that even a short burst of near-maximal exercise can lead to significant structural changes in the blood-gas barrier, such as increased thickness and the leakage of blood from pulmonary capillaries. This occurred even though the ponies’ pulmonary vascular pressures were significantly lower than those seen in racehorses.
Cite This Article
APA
Erickson HH, McAvoy JL, Westfall JA.
(1997).
Exercise-induced changes in the lung of Shetland ponies: ultrastructure and morphometry.
J Submicrosc Cytol Pathol, 29(1), 65-72.
Publication
Researcher Affiliations
- Department of Anatomy and Physiology, College of Veterinary Medicine, Kansas State University, Manhattan 66506-5602, USA.
MeSH Terms
- Animals
- Blood Pressure / physiology
- Heart Rate / physiology
- Horses
- Image Processing, Computer-Assisted
- Lung / anatomy & histology
- Lung / pathology
- Lung / ultrastructure
- Male
- Physical Conditioning, Animal / adverse effects
Citations
This article has been cited 1 times.- Poole DC, Erickson HH. Exercise-induced pulmonary hemorrhage: where are we now?. Vet Med (Auckl) 2016;7:133-148.
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