Vasodilator reserve in respiratory muscles during maximal exertion in ponies.
Abstract: Eight healthy adult grade ponies were studied at rest as well as during maximal exertion carried out with and without adenosine infusion (3 microM X kg-1 X min-1 into the pulmonary artery) on a treadmill to compare levels of blood flow in respiratory muscles with those in other vigorously working muscles and to ascertain whether there remained any unutilized vasodilator reserve in respiratory muscles of maximally exercising ponies. Radionuclide-labeled 15-micron-diam microspheres, injected into the left ventricle, were used to study tissue blood flows. During maximal exertion, there were increases above base-line values in heart rate (336%), mean aortic pressure (41%), cardiac output (722%), and arterial O2 content (56%). The whole-body O2 consumption was 123 +/- 11 ml X min-1 X kg-1, and the stride/respiratory frequency of the galloping ponies was 138 +/- 4/min. With adenosine infusion during maximal exertion, mean aortic pressure decreased (P less than 0.05), but none of the above variables was different from maximal exercise alone. During maximal exertion, blood flow in the adrenal glands, myocardium, respiratory, and limb muscles increased, whereas that in the kidneys decreased and the cerebral perfusion remained unaltered. With adenosine infusion during maximal exercise, renal vasoconstriction intensified, whereas adrenal and coronary beds exhibited further vasodilatation. During maximal exertion, blood flow in the equine diaphragm (265 +/- 36 ml X min-1 X 100 g-1) was not different from that in the gluteus medius (253 +/- 36) and biceps femoris (233 +/- 29); both are principal muscles of propulsion in the equine subjects) or the triceps brachii (227 +/- 26) muscles.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1986-05-01 PubMed ID: 3710976DOI: 10.1152/jappl.1986.60.5.1571Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research article explores the study of eight healthy adult ponies as they underwent maximal exertion with and without adenosine infusion to examine comparitive blood flow levels in respiratory muscles and other heavily used muscles. The study also aimed to determine if there was any unused vasodilator reserve in the respiratory muscles of the ponies during their maximum amount of exercise.
Methodology
- The ponies were evaluated both at rest and during periods of maximal effort on a treadmill. This exertion was done both with and without the infusion of adenosine into the pulmonary artery.
- Radionuclide-labeled microspheres, which had a diameter of 15 microns, were injected into the left ventricle to assess tissue blood flow levels.
- The parameters such as heart rate, mean aortic pressure, cardiac output, and arterial oxygen content; were measured during maximal effort.
Findings
- During maximum exertion, there was an increase in heart rate, mean aortic pressure, cardiac output, and arterial O2 content from the baseline values.
- Adenosine infusion observed during maximum exertion decreased the mean aortic pressure but didn’t significantly modify the other variables compared to just maximal exercise.
- Increased blood flow was noted in the adrenal glands, myocardium, respiratory, and limb muscles, while decreased blood flow was observed in the kidneys. The cerebral perfusion remained the same.
- With adenosine infusion during maximal exercise, renal vasoconstriction intensified, but the adrenal and coronary beds showed further dilation.
Conclusion
- The blood flow in the ponies’ diaphragm wasn’t significantly different from that in several crucial muscles that drive propulsion in horses, such as the gluteus medius and biceps femoris, or the triceps brachii muscles.
- The researchers concluded that the study provided useful insights into the behaviors and conditions of vasodilator reserves in vigorously working muscles during maximum exertion, aiding in better understanding the physiological response of horses to strenuous exercise.
Cite This Article
APA
Manohar M.
(1986).
Vasodilator reserve in respiratory muscles during maximal exertion in ponies.
J Appl Physiol (1985), 60(5), 1571-1577.
https://doi.org/10.1152/jappl.1986.60.5.1571 Publication
Researcher Affiliations
MeSH Terms
- Adenosine / pharmacology
- Animals
- Diaphragm / blood supply
- Diaphragm / physiology
- Female
- Hemodynamics
- Horses / physiology
- Intercostal Muscles / blood supply
- Intercostal Muscles / physiology
- Male
- Muscle, Smooth / blood supply
- Muscle, Smooth / physiology
- Physical Exertion
- Regional Blood Flow / drug effects
- Vascular Resistance / drug effects
- Vasodilation
- Work of Breathing
Citations
This article has been cited 9 times.- Katz LM, Stallard J, Holtby A, Hill EW, Allen K, Sweeney J. Inspiratory muscle training in young, race-fit Thoroughbred racehorses during a period of detraining. PLoS One 2020;15(4):e0225559.
- Sheel AW, Boushel R, Dempsey JA. Competition for blood flow distribution between respiratory and locomotor muscles: implications for muscle fatigue. J Appl Physiol (1985) 2018 Sep 1;125(3):820-831.
- Smith JR, Ferguson SK, Hageman KS, Harms CA, Poole DC, Musch TI. Dietary nitrate supplementation opposes the elevated diaphragm blood flow in chronic heart failure during submaximal exercise. Respir Physiol Neurobiol 2018 Jan;247:140-145.
- Smith JR, Hageman KS, Harms CA, Poole DC, Musch TI. Effect of chronic heart failure in older rats on respiratory muscle and hindlimb blood flow during submaximal exercise. Respir Physiol Neurobiol 2017 Sep;243:20-26.
- Smith JR, Hageman KS, Harms CA, Poole DC, Musch TI. Respiratory muscle blood flow during exercise: Effects of sex and ovarian cycle. J Appl Physiol (1985) 2017 Apr 1;122(4):918-924.
- Joyner MJ, Casey DP. Regulation of increased blood flow (hyperemia) to muscles during exercise: a hierarchy of competing physiological needs. Physiol Rev 2015 Apr;95(2):549-601.
- Manohar M. Transmural coronary vasodilator reserve and flow distribution during maximal exercise in normal and splenectomized ponies. J Physiol 1987 Jun;387:425-40.
- Donaldson LL. A review of the pathophysiology of exercise-induced pulmonary haemorrhage in the equine athlete. Vet Res Commun 1991;15(3):211-26.
- Dempsey JA, Morgan BJ. Obligatory neural feedback control of exercise cardiorespiratory function and performance. J Appl Physiol (1985) 2025 Dec 1;139(6):1527-1544.
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