Anti-hypotensive treatment and endothelin blockade synergistically antagonize exercise fatigue in rats under simulated high altitude.

Abstract

Rapid ascent to high altitude causes illness and fatigue, and there is a demand for effective acute treatments to alleviate such effects. We hypothesized that increased oxygen delivery to the tissue using a combination of a hypertensive agent and an endothelin receptor A antagonist drugs would limit exercise-induced fatigue at simulated high altitude. Our data showed that the combination of 0.1 mg/kg ambrisentan with either 20 mg/kg ephedrine or 10 mg/kg methylphenidate significantly improved exercise duration in rats at simulated altitude of 4,267 m, whereas the individual compounds did not. In normoxic, anesthetized rats, ephedrine alone and in combination with ambrisentan increased heart rate, peripheral blood flow, carotid and pulmonary arterial pressures, breathing rate, and vastus lateralis muscle oxygenation, but under inspired hypoxia, only the combination treatment significantly enhanced muscle oxygenation. Our results suggest that sympathomimetic agents combined with endothelin-A receptor blockers offset altitude-induced fatigue in rats by synergistically increasing the delivery rate of oxygen to hypoxic muscle by concomitantly augmenting perfusion pressure and improving capillary conductance in the skeletal muscle. Our findings might therefore serve as a basis to develop an effective treatment to prevent high-altitude illness and fatigue in humans.

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Citation

Published Version (Please cite this version)

10.1371/journal.pone.0099309

Publication Info

Radiloff, Daniel, Yulin Zhao, Alina Boico, Gert Blueschke, Gregory Palmer, Andrew Fontanella, Mark Dewhirst, Claude A Piantadosi, et al. (2014). Anti-hypotensive treatment and endothelin blockade synergistically antagonize exercise fatigue in rats under simulated high altitude. PLoS One, 9(6). p. e99309. 10.1371/journal.pone.0099309 Retrieved from https://hdl.handle.net/10161/10340.

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Scholars@Duke

Palmer

Gregory M. Palmer

Professor of Radiation Oncology

Greg Palmer obtained his B.S. in Biomedical Engineering from Marquette University in 2000, after which he obtained his Ph.D. in BME from the University of Wisconsin, Madison. He is currently an Associate Professor in the Department of Radiation Oncology, Cancer Biology Division at Duke University Medical Center. His primary research focus has been identifying and exploiting the changes in absorption, scattering, and fluorescence properties of tissue associated with cancer progression and therapeutic response. To this end he has implemented a model-based approach for extracting absorber and scatterer properties from diffuse reflectance and fluorescence measurements. More recently he has developed quantitative imaging methodologies for intravital microscopy to characterize tumor functional and molecular response to radiation and chemotherapy. His awards have included the Jack Fowler Award from the Radiation Research Society.

Laboratory Website:
https://radonc.duke.edu/research-education/research-labs/radiation-and-cancer-biology/palmer-lab

Piantadosi

Claude Anthony Piantadosi

Professor Emeritus of Medicine

Dr. Piantadosi's laboratory has special expertise in the pathogenic mechanisms of acute organ failure, particularly acute lung injury (ALI), with an emphasis on the molecular regulatory roles of the physiological gases— oxygen, carbon monoxide, and nitric oxide— as they relate to the damage responses to acute inflammation. The basic science focuses on oxidative processes and redox-regulation, especially the molecular mechanisms by which reactive oxygen and nitrogen species transmit biological signals involved in the maintenance of energy metabolism and mitochondrial health, but also contribute to pathogenesis and to the resolution of tissue injury.

Clinically, ALI and the related syndrome of multiple organ failure has a high mortality, which is related to the host inflammatory response, but is not well understood scientifically; thus, the laboratory is devoted to understanding these mechanisms in the context of the host response to relevant but well-controlled experimental manipulations including hyperoxia, bacterial infections, toxic drugs, and cytokine/chemokine signals. The approach relies on animal models, mainly transgenic and knockout mice, and cell models, especially lung and heart cells to evaluate and understand the physiology, pathology, and cell and molecular biology of the injury responses, to test independent and integrated mechanisms, and to devise interventions to prevent damage.

Apart from the lung, significant work is devoted to understanding damage to the heart, brain, liver, and kidney caused by these immune mechanisms, specifically emphasizing the role of mitochondria, key targets and sources of oxidative damage. This damage compromises their ability to support energy homeostasis and advanced cellular functions, and impacts on the important roles these organelles play in cell death by apoptosis and necrosis as well as in the resolution of cellular damage and inflammation.


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