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Stray-Gundersen S, Wojan F, Tanaka H, Lalande S. Similar endothelium-dependent vascular responses to intermittent hypoxia in young and older adults. J Appl Physiol (1985) 2024; 137:254-261. [PMID: 38932685 DOI: 10.1152/japplphysiol.00823.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 06/04/2024] [Accepted: 06/24/2024] [Indexed: 06/28/2024] Open
Abstract
Aging is associated with vascular endothelial dysfunction observed through a progressive loss of flow-mediated dilation caused partly by a decreased nitric oxide bioavailability. Intermittent hypoxia, consisting of alternating short bouts of breathing hypoxic and normoxic air, was reported to either maintain or improve vascular function in young adults. The aim of this study was to determine the impact of age on the vascular response to intermittent hypoxia. Twelve young adults and 11 older adults visited the laboratory on two occasions. Plasma nitrate concentrations and brachial artery flow-mediated dilation were assessed before and after exposure to either intermittent hypoxia or a sham protocol. Intermittent hypoxia consisted of eight 4-min hypoxic cycles at a targeted oxygen saturation of 80% interspersed with breathing room air to resaturation, and the sham protocol consisted of eight 4-min normoxic cycles interspersed with breathing room air. Vascular responses were assessed during intermittent hypoxia and the sham protocol. Intermittent hypoxia elicited a brachial artery vasodilation but did not change brachial artery shear rate in both young and older adults. Plasma nitrate concentrations were not significantly affected by intermittent hypoxia compared with the sham protocol in both groups. Brachial artery flow-mediated dilation was not acutely affected by intermittent hypoxia or the sham protocol in either young or older adults. In conclusion, the brachial artery vasodilatory response to intermittent hypoxia was not influenced by age. Intermittent hypoxia increased brachial artery diameter but did not acutely affect endothelium-dependent vasodilation in young or older adults.NEW & NOTEWORTHY The objective of this study was to determine the impact of age on the vascular response to intermittent hypoxia. Eight 4-min bouts of hypoxia at a targeted oxygen saturation of 80% induced a brachial artery vasodilation in both young and older adults, indicating that age does not influence the vasodilatory response to intermittent hypoxia. Intermittent hypoxia did not acutely affect brachial artery flow-mediated dilation in young or older adults.
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Affiliation(s)
- Sten Stray-Gundersen
- Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, Texas, United States
| | - Frank Wojan
- Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, Texas, United States
| | - Hirofumi Tanaka
- Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, Texas, United States
| | - Sophie Lalande
- Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, Texas, United States
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Freire TC, Ferreira MS, De Angelis K, Paula-Ribeiro M. Respiratory, cardiovascular and musculoskeletal mechanisms involved in the pathophysiology of pulmonary hypertension: An updated systematic review of preclinical and clinical studies. Heart Lung 2024; 68:81-91. [PMID: 38941771 DOI: 10.1016/j.hrtlng.2024.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 04/22/2024] [Accepted: 06/04/2024] [Indexed: 06/30/2024]
Abstract
BACKGROUND Progressive exercise intolerance is a hallmark of pulmonary hypertension (pH), severely impacting patients' independence and quality of life (QoL). Accumulating evidence over the last decade shows that combined abnormalities in peripheral reflexes and target organs contribute to disease progression and exercise intolerance. OBJECTIVE The aim of this study was to review the literature of the last decade on the contribution of the cardiovascular, respiratory, and musculoskeletal systems to pathophysiology and exercise intolerance in pH. METHODS A systematic literature search was conducted using specific terms in PubMed, SciELO, and the Cochrane Library databases for original pre-clinical or clinical studies published between 2013 and 2023. Studies followed randomized controlled/non-randomized controlled and pre-post designs. RESULTS The systematic review identified 25 articles reporting functional or structural changes in the respiratory, cardiovascular, and musculoskeletal systems in pH. Moreover, altered biomarkers in these systems, lower cardiac baroreflex, and heightened peripheral chemoreflex activity seemed to contribute to functional changes associated with poor prognosis and exercise intolerance in pH. Potential therapeutic strategies acutely explored involved manipulating the baroreflex and peripheral chemoreflex, improving cardiovascular autonomic control via cardiac vagal control, and targeting specific pathways such as GPER1, GDF-15, miR-126, and the JMJD1C gene. CONCLUSION Information published in the last 10 years advances the notion that pH pathophysiology involves functional and structural changes in the respiratory, cardiovascular, and musculoskeletal systems and their integration with peripheral reflexes. These findings suggest potential therapeutic targets, yet unexplored in clinical trials, that could assist in improving exercise tolerance and QoL in patients with pH.
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Affiliation(s)
- Thaís C Freire
- Translational Physiology Laboratory, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil; Department of Physiology, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Marília S Ferreira
- Translational Physiology Laboratory, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil; Department of Physiology, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Kátia De Angelis
- Translational Physiology Laboratory, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil; Department of Physiology, Federal University of Sao Paulo, Sao Paulo, Brazil
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Raberin A, Meric H, Mucci P, Lopez Ayerbe J, Durand F. Muscle and cerebral oxygenation during exercise in athletes with exercise-induced hypoxemia: A comparison between sea level and acute moderate hypoxia. Eur J Sport Sci 2019; 20:803-812. [PMID: 31526237 DOI: 10.1080/17461391.2019.1669717] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The objective of the present study was to evaluate the influence of exercise-induced hypoxemia (EIH) on muscle and cerebral oxygenation responses during maximal exercise in normoxia and in acute moderate hypoxia (fraction of inspired oxygen: 15.3%, 2400 m). EIH was defined as a drop in hemoglobin saturation of at least 4% for at least three consecutive minutes during maximal exercise at sea level. Twenty-five athletes performed incremental treadmill tests to assess maximal oxygen consumption (VO2max) in normoxia and in hypoxia. Oxygenation of the vastus lateralis muscle and the left prefrontal cortex of the brain was monitored using near-infrared spectroscopy. During the normoxic test, 15 athletes exhibited EIH; they displayed a larger change in muscle levels of oxyhemoglobin (ΔO2Hb) (p = 0.04) and a greater change in cerebral levels of deoxyhemoglobin (ΔHHb) (p = 0.02) than athletes without EIH (NEIH group). During the hypoxic test, muscle ΔO2Hb was lower in the EIH group than in the NEIH group (p = 0.03). At VO2max, hypoxia was associated with a smaller cerebral ΔO2Hb in both groups, and a greater cerebral ΔHHb compared to normoxia in the NEIH group only (p = 0.02). No intergroup differences in changes in muscle oxygenation were observed. The severity of O2 arterial desaturation was negatively correlated with changes in total muscle hemoglobin in normoxia (r = -0.48, p = 0.01), and positively correlated with the cerebral ΔHHb in normoxia (r = 0.45, p = 0.02). The occurrence of EIH at sea level was associated with specific muscle and cerebral oxygenation responses to exercise under both normoxia and moderate hypoxia.
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Affiliation(s)
- Antoine Raberin
- LEPSA, EA 4604, Université de Perpignan Via Domitia, Font Romeu, France
| | - Henri Meric
- LEPSA, EA 4604, Université de Perpignan Via Domitia, Font Romeu, France
| | - Patrick Mucci
- Univ. Lille, Univ. Artois, Univ. Littoral Côte d'Opale, EA 7369 - URePSSS - Unité de Recherche Pluridisciplinaire Sport Santé Société, Lille, France
| | | | - Fabienne Durand
- LEPSA, EA 4604, Université de Perpignan Via Domitia, Font Romeu, France
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Keller‐Ross ML, Sarkinen AL, Chantigian DP, Cross TJ, Johnson BD, Olson TP. Interaction of hypoxia and vascular occlusion on cardiorespiratory responses during exercise. TRANSLATIONAL SPORTS MEDICINE 2018. [DOI: 10.1002/tsm2.60] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Manda L. Keller‐Ross
- Division of Physical Therapy, Medical School University of Minnesota Minneapolis Minnesota
| | | | - Daniel P. Chantigian
- Division of Physical Therapy, Medical School University of Minnesota Minneapolis Minnesota
| | - Troy J. Cross
- Internal Medicine Mayo Clinic College of Medicine Rochester Minnesota
- Menzies Health Institute Queensland, Gold Coast Griffith University QLD Australia
| | - Bruce D. Johnson
- Internal Medicine Mayo Clinic College of Medicine Rochester Minnesota
| | - Thomas P. Olson
- Internal Medicine Mayo Clinic College of Medicine Rochester Minnesota
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Klenze H, Köhler TC, Farquharson F, Walterspacher S, Duerschmied D, Roecker K, Kabitz HJ, Walker DJ. Resting limb muscle perfusion during inspiratory muscle loading in hypoxia and normoxia. Respir Physiol Neurobiol 2017. [PMID: 28625661 DOI: 10.1016/j.resp.2017.06.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
INTRODUCTION Fatiguing of respiratory muscles reduces peripheral muscle perfusion. Further, acute hypoxia enhances respiratory muscle fatigue. This study investigated the effects of inspiratory muscle loading (IML) on resting locomotor muscle perfusion in hypoxia compared to normoxia. METHODS Ten subjects completed two study days of fatiguing IML (blinded, randomized) in normobaric hypoxia (targeted oxygen saturation 80%) and normoxia, respectively. Contrast-enhanced ultrasound (CEUS) of the gastrocnemius muscle and popliteal doppler ultrasonography were used to monitor muscle perfusion. Based on CEUS and monitored cardiac output, perfusion surrogate parameters (CLPaer and CLPap) were established. RESULTS Muscle perfusion declines early during IML in normoxia (CLPaer: -54±25%, p<0.01; CLPap: -58±32%, p<0.01) and hypoxia (CLPaer: -43±23%, p<0.01; CLPap: -41±20%, p<0.01). Hypoxia compared to normoxia increased cardiac output before (+23±19%, p<0.01 ANOVA) and during (+22±20%, p<0.01 ANOVA) IML, while local muscle perfusion during IML remained unchanged (CLPaer: p=0.41 ANOVA; CLPap: p=0.29 ANOVA). CONCLUSION Acute hypoxia compared to normoxia does not affect locomotor muscle perfusion during fatiguing IML.
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Affiliation(s)
- Hannes Klenze
- Department of Pneumology and Intensive Care Medicine, Academic Teaching Hospital Klinikum Konstanz, Germany.
| | | | - Franziska Farquharson
- Department of Pneumology and Intensive Care Medicine, Academic Teaching Hospital Klinikum Konstanz, Germany
| | - Stephan Walterspacher
- Department of Pneumology and Intensive Care Medicine, Academic Teaching Hospital Klinikum Konstanz, Germany; Department of Medicine/Pneumology, Faculty of Health, Witten/Herdecke University, Witten, Germany
| | - Daniel Duerschmied
- Cardiology and Angiology I, University Heart Center Freiburg - Bad Krozingen and Interdisciplinary Medical Intensive Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Kai Roecker
- Department of Applied Public Health (AGW), Furtwangen University, Germany
| | - Hans-Joachim Kabitz
- Department of Pneumology and Intensive Care Medicine, Academic Teaching Hospital Klinikum Konstanz, Germany
| | - David Johannes Walker
- Department of Pneumology and Intensive Care Medicine, Academic Teaching Hospital Klinikum Konstanz, Germany; Department of Medicine/Pneumology, Faculty of Health, Witten/Herdecke University, Witten, Germany
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Kim HJ, Yoo HY, Lin HY, Oh GT, Zhang YH, Kim SJ. Role of muscular eNOS in skeletal arteries: Endothelium-independent hypoxic vasoconstriction of the femoral artery is impaired in eNOS-deficient mice. Am J Physiol Cell Physiol 2016; 311:C508-17. [PMID: 27486092 DOI: 10.1152/ajpcell.00061.2016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 07/19/2016] [Indexed: 11/22/2022]
Abstract
We previously reported that hypoxia augments α-adrenergic contraction (hypoxic vasoconstriction, HVC) of skeletal arteries in rats. The underlying mechanism may involve hypoxic inhibition of endothelial nitric oxide synthase (eNOS) expressed in skeletal arterial myocytes (16). To further explore the novel role of muscular eNOS in the skeletal artery, we compared HVC in femoral arteries (FAs) from eNOS knockout (KO) mice with that from wild-type (WT) and heterozygous (HZ) mice. Immunohistochemical assays revealed that, in addition to endothelia, eNOS is also expressed in the medial layer of FAs, albeit at a much lower level. However, the medial eNOS signal was not evident in HZ FAs, despite strong expression in the endothelium; similar observations were made in WT carotid arteries (CAs). The amplitude of contraction induced by 1 μM phenylephrine (PhE) was greater in HZ than in WT FAs. Hypoxia (3% Po2) significantly augmented PhE-induced contraction in WT FAs but not in HZ or KO FAs. No HVC was observed in PhE-pretreated WT CAs. The NOS inhibitor nitro-l-arginine methyl ester (0.1 mM) also augmented PhE contraction in endothelium-denuded WT FAs but not in WT CAs. Inhibitors specific to neuronal NOS and inducible NOS did not augment PhE-induced contraction of WT FAs. NADPH oxidase 4 (NOX4) inhibitor (GKT137831, 5 μM), but not NOX2 inhibitor (apocynin, 100 μM), suppressed HVC. Consistent with the role of reactive oxygen species (ROS), HVC was also inhibited by pretreatment with tiron or polyethylene glycol-catalase. Taken together, these data suggest that the eNOS expressed in smooth muscle cells in FAs attenuates α-adrenergic vasoconstriction; this suppression is alleviated under hypoxia, which potentiates vasoconstriction in a NOX4/ROS-dependent mechanism.
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Affiliation(s)
- Hae Jin Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Hae Young Yoo
- Chung-Ang University Red Cross College of Nursing, Seoul, Korea; and
| | - Hai Yue Lin
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea
| | - Goo Taeg Oh
- Department of Life Sciences, Ewha Womans University, Seoul, Korea
| | - Yin Hua Zhang
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Sung Joon Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea;
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Joyner MJ, Casey DP. Regulation of increased blood flow (hyperemia) to muscles during exercise: a hierarchy of competing physiological needs. Physiol Rev 2015; 95:549-601. [PMID: 25834232 DOI: 10.1152/physrev.00035.2013] [Citation(s) in RCA: 430] [Impact Index Per Article: 47.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This review focuses on how blood flow to contracting skeletal muscles is regulated during exercise in humans. The idea is that blood flow to the contracting muscles links oxygen in the atmosphere with the contracting muscles where it is consumed. In this context, we take a top down approach and review the basics of oxygen consumption at rest and during exercise in humans, how these values change with training, and the systemic hemodynamic adaptations that support them. We highlight the very high muscle blood flow responses to exercise discovered in the 1980s. We also discuss the vasodilating factors in the contracting muscles responsible for these very high flows. Finally, the competition between demand for blood flow by contracting muscles and maximum systemic cardiac output is discussed as a potential challenge to blood pressure regulation during heavy large muscle mass or whole body exercise in humans. At this time, no one dominant dilator mechanism accounts for exercise hyperemia. Additionally, complex interactions between the sympathetic nervous system and the microcirculation facilitate high levels of systemic oxygen extraction and permit just enough sympathetic control of blood flow to contracting muscles to regulate blood pressure during large muscle mass exercise in humans.
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Affiliation(s)
- Michael J Joyner
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, Iowa
| | - Darren P Casey
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, Iowa
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Laughlin MH, Davis MJ, Secher NH, van Lieshout JJ, Arce-Esquivel AA, Simmons GH, Bender SB, Padilla J, Bache RJ, Merkus D, Duncker DJ. Peripheral circulation. Compr Physiol 2013; 2:321-447. [PMID: 23728977 DOI: 10.1002/cphy.c100048] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Blood flow (BF) increases with increasing exercise intensity in skeletal, respiratory, and cardiac muscle. In humans during maximal exercise intensities, 85% to 90% of total cardiac output is distributed to skeletal and cardiac muscle. During exercise BF increases modestly and heterogeneously to brain and decreases in gastrointestinal, reproductive, and renal tissues and shows little to no change in skin. If the duration of exercise is sufficient to increase body/core temperature, skin BF is also increased in humans. Because blood pressure changes little during exercise, changes in distribution of BF with incremental exercise result from changes in vascular conductance. These changes in distribution of BF throughout the body contribute to decreases in mixed venous oxygen content, serve to supply adequate oxygen to the active skeletal muscles, and support metabolism of other tissues while maintaining homeostasis. This review discusses the response of the peripheral circulation of humans to acute and chronic dynamic exercise and mechanisms responsible for these responses. This is accomplished in the context of leading the reader on a tour through the peripheral circulation during dynamic exercise. During this tour, we consider what is known about how each vascular bed controls BF during exercise and how these control mechanisms are modified by chronic physical activity/exercise training. The tour ends by comparing responses of the systemic circulation to those of the pulmonary circulation relative to the effects of exercise on the regional distribution of BF and mechanisms responsible for control of resistance/conductance in the systemic and pulmonary circulations.
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Affiliation(s)
- M Harold Laughlin
- Department of Medical Pharmacology and Physiology, and the Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA.
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9
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Donnelly J, Green S. Effect of hypoxia on the dynamic response of hyperaemia in the contracting human calf muscle. Exp Physiol 2012; 98:81-93. [PMID: 22689444 DOI: 10.1113/expphysiol.2012.066258] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although systemic hypoxia increases the muscle hyperaemic response during 'steady-state' exercise, its effect on the dynamic characteristics of this response is not clear. In the present study, we first established that hypoxia increases the steady-state hyperaemic response at low workloads during calf exercise. To study dynamic aspects of this response, eight subjects performed eight exercise trials while breathing a normoxic (fractional inspired O(2) = 0.2094) or hypoxic gas mixture (fractional inspired O(2) = 0.105). Subjects performed intermittent contractions (1 s) of the calf muscle at 20% maximal voluntary contraction, and the leg blood flow (LBF), leg vascular conductance (LVC) and EMG activities of the triceps surae muscles were measured during each contraction-relaxation period (3 s). The LBF and LVC responses were averaged for each subject and fitted using a four-phase, exponential growth and decay function. Hypoxia evoked significant increases in the change in LBF (15%) and LVC (23%) from the start to the end of exercise, as well as the amplitude of the rapid growth phase of LBF and LVC (21%). Similar, but non-significant, effects on the amplitude of the slow growth phase of LBF (P = 0.08) and LVC (P = 0.10) were observed. By contrast, hypoxia had no effect on temporal parameters of these growth phases, parameters defining the decay phases or EMG activities. These results suggest that the effect of hypoxia on exercise hyperaemia is targeted at the rapid and perhaps the slow growth phase of the response, and is not mediated by a change in the level of muscle activation.
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Affiliation(s)
- J Donnelly
- Department of Physiology, University of Otago, Dunedin, New Zealand
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10
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Stickland MK, Fuhr DP, Haykowsky MJ, Jones KE, Paterson DI, Ezekowitz JA, McMurtry MS. Carotid chemoreceptor modulation of blood flow during exercise in healthy humans. J Physiol 2011; 589:6219-30. [PMID: 22025661 DOI: 10.1113/jphysiol.2011.218099] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Carotid chemoreceptor (CC) inhibition reduces sympathetic nervous outflow in exercising dogs and humans. We sought to determine if CC suppression increases muscle blood flow in humans during exercise and hypoxia. Healthy subjects (N = 13) were evaluated at rest and during constant-work leg extension exercise while exposed to either normoxia or hypoxia (inspired O(2) tension, F(IO(2)), ≈ 0.12, target arterial O(2) saturation = 85%). Subjects breathed hyperoxic gas (F(IO(2)) ≈ 1.0) and/or received intravenous dopamine to inhibit the CC while femoral arterial blood flow data were obtained continuously with pulsed Doppler ultrasound. Exercise increased heart rate, mean arterial pressure, femoral blood flow and conductance compared to rest. Transient hyperoxia had no significant effect on blood flow at rest, but increased femoral blood flow and conductance transiently during exercise without changing blood pressure. Similarly, dopamine had no effect on steady-state blood flow at rest, but increased femoral blood flow and conductance during exercise. The transient vasodilatory response observed by CC inhibition with hyperoxia during exercise could be blocked with simultaneous CC inhibition with dopamine. Despite evidence of dopamine reducing ventilation during hypoxia, no effect on femoral blood flow, conductance or mean arterial pressure was observed either at rest or during exercise with CC inhibition with dopamine while breathing hypoxia. These findings indicate that the carotid chemoreceptor contributes to skeletal muscle blood flow regulation during normoxic exercise in healthy humans, but that the influence of the CC on blood flow regulation in hypoxia is limited.
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Affiliation(s)
- Michael K Stickland
- Division of Pulmonary Medicine, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
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11
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Casey DP, Joyner MJ. Local control of skeletal muscle blood flow during exercise: influence of available oxygen. J Appl Physiol (1985) 2011; 111:1527-38. [PMID: 21885800 DOI: 10.1152/japplphysiol.00895.2011] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Reductions in oxygen availability (O(2)) by either reduced arterial O(2) content or reduced perfusion pressure can have profound influences on the circulation, including vasodilation in skeletal muscle vascular beds. The purpose of this review is to put into context the present evidence regarding mechanisms responsible for the local control of blood flow during acute systemic hypoxia and/or local hypoperfusion in contracting muscle. The combination of submaximal exercise and hypoxia produces a "compensatory" vasodilation and augmented blood flow in contracting muscles relative to the same level of exercise under normoxic conditions. A similar compensatory vasodilation is observed in response to local reductions in oxygen availability (i.e., hypoperfusion) during normoxic exercise. Available evidence suggests that nitric oxide (NO) contributes to the compensatory dilator response under each of these conditions, whereas adenosine appears to only play a role during hypoperfusion. During systemic hypoxia the NO-mediated component of the compensatory vasodilation is regulated through a β-adrenergic receptor mechanism at low-intensity exercise, while an additional (not yet identified) source of NO is likely to be engaged as exercise intensity increases during hypoxia. Potential candidates for stimulating and/or interacting with NO at higher exercise intensities include prostaglandins and/or ATP. Conversely, prostaglandins do not appear to play a role in the compensatory vasodilation during exercise with hypoperfusion. Taken together, the data for both hypoxia and hypoperfusion suggest NO is important in the compensatory vasodilation seen when oxygen availability is limited. This is important from a basic biological perspective and also has pathophysiological implications for diseases associated with either hypoxia or hypoperfusion.
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Affiliation(s)
- Darren P Casey
- Dept. of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
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13
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Limberg JK, Evans TD, Blain GM, Pegelow DF, Danielson JR, Eldridge MW, Proctor LT, Sebranek JJ, Schrage WG. Effect of obesity and metabolic syndrome on hypoxic vasodilation. Eur J Appl Physiol 2011; 112:699-709. [PMID: 21656228 DOI: 10.1007/s00421-011-2025-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 05/23/2011] [Indexed: 12/30/2022]
Abstract
This study was designed to test whether obese adults and adults with metabolic syndrome (MetSyn) exhibit altered hyperemic responses to hypoxia at rest and during forearm exercise when compared with lean controls. We hypothesized blood flow responses due to hypoxia would be lower in young obese subjects (n = 11, 24 ± 2 years, BMI 36 ± 2 kg m(-2)) and subjects with MetSyn (n = 8, 29 ± 3 years BMI 39 ± 2 kg m(-2)) when compared with lean adults (n = 13, 29 ± 2 years, BMI 24 ± 1 kg m(-2)). We measured forearm blood flow (FBF, Doppler Ultrasound) and arterial oxygen saturation (pulse oximetry) during rest and steady-state dynamic forearm exercise (20 contractions/min at 8 and 12 kg) under two conditions: normoxia (0.21 F(i)O(2), ~98% S(a)O(2)) and hypoxia (~0.10 F(i)O(2), 80% S(a)O(2)). Forearm vascular conductance (FVC) was calculated as FBF/mean arterial blood pressure. At rest, the percent change in FVC with hypoxia was greater in adults with MetSyn when compared with lean controls (p = 0.02); obese and lean adult responses were not statistically different. Exercise increased FVC from resting levels in all groups (p < 0.05). Hypoxia caused an additional increase in FVC (p < 0.05) that was not different between groups; responses to hypoxia were heterogeneous within and between groups. Reporting FVC responses as absolute or percent changes led to similar conclusions. These results suggest adults with MetSyn exhibit enhanced hypoxic vasodilation at rest. However, hypoxic responses during exercise in obese adults and adults with MetSyn were not statistically different when compared with lean adults. Individual hypoxic vasodilatory responses were variable, suggesting diversity in vascular control.
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Affiliation(s)
- Jacqueline K Limberg
- Department of Kinesiology, School of Education, University of Wisconsin, 1149 Natatorium, Madison, WI 53706, USA.
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Heinonen IH, Kemppainen J, Kaskinoro K, Peltonen JE, Borra R, Lindroos M, Oikonen V, Nuutila P, Knuuti J, Boushel R, Kalliokoski KK. Regulation of human skeletal muscle perfusion and its heterogeneity during exercise in moderate hypoxia. Am J Physiol Regul Integr Comp Physiol 2010; 299:R72-9. [PMID: 20427728 DOI: 10.1152/ajpregu.00056.2010] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although many effects of both acute and chronic hypoxia on the circulation are well characterized, the distribution and regulation of blood flow (BF) heterogeneity in skeletal muscle during systemic hypoxia is not well understood in humans. We measured muscle BF within the thigh muscles of nine healthy young men using positron emission tomography during one-leg dynamic knee extension exercise in normoxia and moderate physiological systemic hypoxia (14% O(2) corresponding to approximately 3,400 m of altitude) without and with local adenosine receptor inhibition with femoral artery infusion of aminophylline. Systemic hypoxia reduced oxygen extraction of the limb but increased muscle BF, and this flow increment was confined solely to the exercising quadriceps femoris muscle. Exercising muscle BF heterogeneity was reduced from rest (P = 0.055) but was not affected by hypoxia. Adenosine receptor inhibition had no effect on capillary BF during exercise in either normoxia or hypoxia. Finally, one-leg exercise increased muscle BF heterogeneity both in the resting posterior hamstring part of the exercising leg and in the resting contralateral leg, whereas mean BF was unchanged. In conclusion, the results show that increased BF during one-leg exercise in moderate hypoxia is confined only to the contracting muscles, and the working muscle hyperemia appears not to be directly mediated by adenosine. Increased flow heterogeneity in noncontracting muscles likely reflects sympathetic nervous constraints to curtail BF increments in areas other than working skeletal muscles, but this effect is not potentiated in moderate systemic hypoxia during small muscle mass exercise.
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Affiliation(s)
- Ilkka H Heinonen
- Turku PET Centre, Turku University Hospital, University of Turku, Turku, Finland.
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