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Koshika K, Kaneko R, Shionoya M, Shimizu K, Sendai Y, Matsuura N, Akiike Y, Ichinohe T. Involvement of α- and β-Adrenergic Receptors in Skeletal Muscle Blood Flow Changes During Hyper-/Hypocapnia in Anesthetized Rabbits. Anesth Prog 2023; 70:58-64. [PMID: 37379094 PMCID: PMC10328189 DOI: 10.2344/anpr-70-02-02] [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: 02/02/2022] [Accepted: 01/23/2023] [Indexed: 06/29/2023] Open
Abstract
OBJECTIVE This study investigated the involvement of α1- and β2-adrenergic receptors in skeletal muscle blood flow changes during variations in ETCO2. METHODS Forty Japanese White rabbits anesthetized with isoflurane were randomly allocated to 1 of 5 groups: phentolamine, metaproterenol, phenylephrine, butoxamine, and atropine. Heart rate (HR), systolic blood pressure (SBP), common carotid artery blood flow (CCBF), masseter muscle tissue blood flow (MBF), and quadriceps muscle tissue blood flow (QBF) were recorded and analyzed at 3 periods: (1) baseline, (2) during hypercapnia (phentolamine and metaproterenol groups) or hypocapnia (phenylephrine, butoxamine, and atropine groups), and (3) during or after receiving vasoactive agents. RESULTS MBF and QBF decreased during hypercapnia. The decrease in MBF was smaller than that in QBF. SBP and CCBF increased, while HR decreased. Both MBF and QBF recovered to their baseline levels after phentolamine administration. MBF became greater than its baseline level, while QBF did not fully recover after metaproterenol administration. MBF and QBF increased during hypocapnia. The increase rate in MBF was larger than that in QBF. HR, SBP, and CCBF did not change. Both MBF and QBF decreased to ∼90% to 95% of their baseline levels after phenylephrine or butoxamine administration. Atropine showed no effects on MBF and QBF. CONCLUSION These results suggest the skeletal muscle blood flow changes observed during hypercapnia and hypocapnia may mainly involve α1-adrenergic but not β2-adrenergic receptor activity.
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Affiliation(s)
- Kyotaro Koshika
- Associate Professor, Department of Dental Anesthesiology, Tokyo Dental College, Tokyo, Japan
| | - Rumi Kaneko
- Postgraduate Student, Department of Dental Anesthesiology, Tokyo Dental College, Tokyo, Japan
| | - Mai Shionoya
- Postgraduate Student, Department of Dental Anesthesiology, Tokyo Dental College, Tokyo, Japan
| | - Kotaro Shimizu
- Postgraduate Student, Department of Dental Anesthesiology, Tokyo Dental College, Tokyo, Japan
| | - Yuka Sendai
- Postgraduate Student, Department of Dental Anesthesiology, Tokyo Dental College, Tokyo, Japan
| | - Nobutaka Matsuura
- Postgraduate Student, Department of Dental Anesthesiology, Tokyo Dental College, Tokyo, Japan
| | - Yui Akiike
- Senior Assistant Professor, Department of Dental Anesthesiology, Tokyo Dental College, Tokyo, Japan
| | - Tatsuya Ichinohe
- Professor and Chairman, Department of Dental Anesthesiology, Tokyo Dental College, Tokyo, Japan
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2
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Paquin J, Lagacé JC, Brochu M, Dionne IJ. Exercising for Insulin Sensitivity - Is There a Mechanistic Relationship With Quantitative Changes in Skeletal Muscle Mass? Front Physiol 2021; 12:656909. [PMID: 34054574 PMCID: PMC8149906 DOI: 10.3389/fphys.2021.656909] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 04/14/2021] [Indexed: 12/29/2022] Open
Abstract
Skeletal muscle (SM) tissue has been repetitively shown to play a major role in whole-body glucose homeostasis and overall metabolic health. Hence, SM hypertrophy through resistance training (RT) has been suggested to be favorable to glucose homeostasis in different populations, from young healthy to type 2 diabetic (T2D) individuals. While RT has been shown to contribute to improved metabolic health, including insulin sensitivity surrogates, in multiple studies, a universal understanding of a mechanistic explanation is currently lacking. Furthermore, exercised-improved glucose homeostasis and quantitative changes of SM mass have been hypothesized to be concurrent but not necessarily causally associated. With a straightforward focus on exercise interventions, this narrative review aims to highlight the current level of evidence of the impact of SM hypertrophy on glucose homeostasis, as well various mechanisms that are likely to explain those effects. These mechanistic insights could provide a strengthened rationale for future research assessing alternative RT strategies to the current classical modalities, such as low-load, high repetition RT or high-volume circuit-style RT, in metabolically impaired populations.
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Affiliation(s)
- Jasmine Paquin
- Research Centre on Aging, Affiliated With CIUSSS de l'Estrie-CHUS, Sherbrooke, QC, Canada.,Faculty of Physical Activity Sciences, University of Sherbrooke, Sherbrooke, QC, Canada
| | - Jean-Christophe Lagacé
- Research Centre on Aging, Affiliated With CIUSSS de l'Estrie-CHUS, Sherbrooke, QC, Canada.,Faculty of Physical Activity Sciences, University of Sherbrooke, Sherbrooke, QC, Canada
| | - Martin Brochu
- Research Centre on Aging, Affiliated With CIUSSS de l'Estrie-CHUS, Sherbrooke, QC, Canada.,Faculty of Physical Activity Sciences, University of Sherbrooke, Sherbrooke, QC, Canada
| | - Isabelle J Dionne
- Research Centre on Aging, Affiliated With CIUSSS de l'Estrie-CHUS, Sherbrooke, QC, Canada.,Faculty of Physical Activity Sciences, University of Sherbrooke, Sherbrooke, QC, Canada
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3
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Poole DC, Behnke BJ, Musch TI. The role of vascular function on exercise capacity in health and disease. J Physiol 2021; 599:889-910. [PMID: 31977068 PMCID: PMC7874303 DOI: 10.1113/jp278931] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 12/10/2019] [Indexed: 12/16/2022] Open
Abstract
Three sentinel parameters of aerobic performance are the maximal oxygen uptake ( V ̇ O 2 max ), critical power (CP) and speed of the V ̇ O 2 kinetics following exercise onset. Of these, the latter is, perhaps, the cardinal test of integrated function along the O2 transport pathway from lungs to skeletal muscle mitochondria. Fast V ̇ O 2 kinetics demands that the cardiovascular system distributes exercise-induced blood flow elevations among and within those vascular beds subserving the contracting muscle(s). Ideally, this process must occur at least as rapidly as mitochondrial metabolism elevates V ̇ O 2 . Chronic disease and ageing create an O2 delivery (i.e. blood flow × arterial [O2 ], Q ̇ O 2 ) dependency that slows V ̇ O 2 kinetics, decreasing CP and V ̇ O 2 max , increasing the O2 deficit and sowing the seeds of exercise intolerance. Exercise training, in contrast, does the opposite. Within the context of these three parameters (see Graphical Abstract), this brief review examines the training-induced plasticity of key elements in the O2 transport pathway. It asks how structural and functional vascular adaptations accelerate and redistribute muscle Q ̇ O 2 and thus defend microvascular O2 partial pressures and capillary blood-myocyte O2 diffusion across a ∼100-fold range of muscle V ̇ O 2 values. Recent discoveries, especially in the muscle microcirculation and Q ̇ O 2 -to- V ̇ O 2 heterogeneity, are integrated with the O2 transport pathway to appreciate how local and systemic vascular control helps defend V ̇ O 2 kinetics and determine CP and V ̇ O 2 max in health and how vascular dysfunction in disease predicates exercise intolerance. Finally, the latest evidence that nitrate supplementation improves vascular and therefore aerobic function in health and disease is presented.
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Affiliation(s)
- David C Poole
- Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA
| | - Brad J Behnke
- Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA
| | - Timothy I Musch
- Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA
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4
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Colburn TD, Hirai DM, Craig JC, Ferguson SK, Weber RE, Schulze KM, Behnke BJ, Musch TI, Poole DC. Transcapillary PO 2 gradients in contracting muscles across the fibre type and oxidative continuum. J Physiol 2020; 598:3187-3202. [PMID: 32445225 DOI: 10.1113/jp279608] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 05/14/2020] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Within skeletal muscle the greatest resistance to oxygen transport is thought to reside across the short distance at the red blood cell-myocyte interface. These structures generate a significant transmural oxygen pressure (PO2 ) gradient in mixed fibre-type muscle. Increasing O2 flux across the capillary wall during exercise depends on: (i) the transmural O2 pressure gradient, which is maintained in mixed-fibre muscle, and/or (ii) elevating diffusing properties between microvascular and interstitial compartments resulting, in part, from microvascular haemodynamics and red blood cell distribution. We evaluated the PO2 within the microvascular and interstitial spaces of muscles spanning the slow- to fast-twitch fibre and high- to low-oxidative capacity spectrums, at rest and during contractions, to assess the magnitude of transcapillary PO2 gradients in rats. Our findings demonstrate that, across the metabolic rest-contraction transition, the transcapillary pressure gradient for O2 flux is: (i) maintained in all muscle types, and (ii) the lowest in contracting highly oxidative fast-twitch muscle. ABSTRACT In mixed fibre-type skeletal muscle transcapillary PO2 gradients (PO2 mv-PO2 is; microvascular and interstitial, respectively) drive O2 flux across the blood-myocyte interface where the greatest resistance to that O2 flux resides. We assessed a broad spectrum of fibre-type and oxidative-capacity rat muscles across the rest-to-contraction (1 Hz, 120 s) transient to test the novel hypotheses that: (i) slow-twitch PO2 is would be greater than fast-twitch, (ii) muscles with greater oxidative capacity have greater PO2 is than glycolytic counterparts, and (iii) whether PO2 mv-PO2 is at rest is maintained during contractions across all muscle types. PO2 mv and PO2 is were determined via phosphorescence quenching in soleus (SOL; 91% type I+IIa fibres and CSa: ∼21 μmol min-1 g-1 ), peroneal (PER; 33% and ∼20 μmol min-1 g-1 ), mixed (MG; 9% and ∼26 μmol min-1 g-1 ) and white gastrocnemius (WG; 0% and ∼8 μmol min-1 g-1 ) across the rest-contraction transient. PO2 mv was higher than PO2 is in each muscle (∼6-13 mmHg; P < 0.05). SOL PO2 isarea was greater than in the fast-twitch muscles during contractions (P < 0.05). Oxidative muscles had greater PO2 isnadir (9.4 ± 0.8, 7.4 ± 0.9 and 6.4 ± 0.4; SOL, PER and MG, respectively) than WG (3.0 ± 0.3 mmHg, P < 0.05). The magnitude of PO2 mv-PO2 is at rest decreased during contractions in MG only (∼11 to 7 mmHg; time × (PO2 mv-PO2 is) interaction, P < 0.05). These data support the hypothesis that, since transcapillary PO2 gradients during contractions are maintained in all muscle types, increased O2 flux must occur via enhanced intracapillary diffusing conductance, which is most extreme in highly oxidative fast-twitch muscle.
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Affiliation(s)
| | - Daniel M Hirai
- Department of Health and Kinesiology, Purdue University, West Lafayette, IN
| | - Jesse C Craig
- Department of Internal Medicine, University of Utah, Salt Lake City, UT
| | - Scott K Ferguson
- Department of Kinesiology and Exercise Sciences, University of Hawaii, Hilo, HI
| | - Ramona E Weber
- Department of Kinesiology, Kansas State University Manhattan, KS
| | - Kiana M Schulze
- Department of Kinesiology, Kansas State University Manhattan, KS
| | - Brad J Behnke
- Department of Kinesiology, Kansas State University Manhattan, KS
| | - Timothy I Musch
- Department of Kinesiology, Kansas State University Manhattan, KS.,Department of Anatomy and Physiology, Kansas State University Manhattan, KS
| | - David C Poole
- Department of Kinesiology, Kansas State University Manhattan, KS.,Department of Anatomy and Physiology, Kansas State University Manhattan, KS
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5
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The Impact of Different Exercise Intensities on Vasodilation and Shear Rate Patterns in Children. Pediatr Exerc Sci 2019; 31:282-289. [PMID: 31177912 DOI: 10.1123/pes.2019-0003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 04/22/2019] [Accepted: 04/24/2019] [Indexed: 11/18/2022]
Abstract
PURPOSE The effect of exercise intensity on vasodilator function is poorly understood in children. The authors compared the acute effect of high-intensity interval exercise (HIIE) with moderate-intensity steady-state exercise (MISS) on postexercise vasodilation and shear patterns in 7- to 12- year-old children. METHODS Superficial femoral artery diameter, shear rates, and flow-mediated dilation were measured pre, immediately following (post), and 1 hour after (post60) HIIE (six 1-min sprints at 90% peak power [Wmax], with 1-min recovery) and MISS (15 min at 44% Wmax). RESULTS Baseline superficial femoral artery diameter increased similarly following both HIIE (pre 4.23 [0.41] mm, post 4.73 [0.56] mm) and MISS (pre 4.28 [0.56] mm, post 4.59 [0.64] mm), returning to preexercise values post60. Blood flow and antegrade shear rate were increased post HIIE and MISS, but to a greater extent, post HIIE (P < .05). Retrograde shear rate was attenuated post both exercise conditions and remained post60 (P < .001). There was a decline in flow-mediated dilation postexercise (HIIE Δ -2.9%; MISS Δ -2.4%), which was no longer apparent when corrected for baseline diameter. CONCLUSION Acute bouts of external work-matched HIIE or MISS exert a similar impact on shear-mediated conduit artery vasodilation and flow-mediated dilation in children, and this is reversed 1 hour after exercise.
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Finkel A, Röhrich MA, Maassen N, Lützow M, Blau LS, Hanff E, Tsikas D, Maassen M. Long-term effects of NO3- on the relationship between oxygen uptake and power after three weeks of supplemented HIHVT. J Appl Physiol (1985) 2018; 125:1997-2007. [PMID: 30359537 DOI: 10.1152/japplphysiol.00176.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The aim of this study was to investigate the later effects of daily NO3- supplementation over 3 wk of training on the relationship between O2 uptake and power at different intensities with an incremental test (IT), a double-wingate test (WT), and an endurance capacity test at 80% Wmax (ECT) before and after the supplementation period. Seventeen male recreational athletes participated in this double-blind placebo (PL)-controlled study. Subjects participated in a 3-wk intermittent high-intensity, high-volume training period with 45 intervals of Wmax - 10 W and an active recovery period of 10 W in between with dietary NO3- (NaNO3) or placebo supplementation (NaCl) (both 8.5 mg·kg-1·day-1) on a cycle ergometer. During a training session, plasma [ NO3- ] ( P < 0.001) and plasma [ NO2- ] ( P < 0.01) were higher in nitrate (N), whereas in pre- and posttests mean plasma [ NO3- ] and [ NO2- ] were not different between groups. In the WT [48 h after cessation of supplementation (C)], the ratio between V̇o2 and power decreased in N ( P < 0.01) with no changes in PL. Endurance capacity (4-5 days after C) similarly increased in both groups ( P < 0.01). However, the total oxygen consumption decreased by 5% ( P < 0.01) in N, with no change in PL. The slope of V̇o2·W-1 in IT (5-7 days after C) decreased in N ( P < 0.01), whereas no changes were found in PL. During low- and moderate-intensity workloads, no changes and differences in V̇o2 could be detected. We conclude that nitrate supplementation causes a sustaining reduction of the oxygen cost per watt during exercise with a large recruitment of type II muscle fibers without affecting endurance capacity. NEW & NOTEWORTHY Because most studies focused on the acute effects of NO3- supplementation on exercise performance during a supplementation period, the sustainability of the effects of the NO3- supplementation remain unknown. We followed the development of V̇o2/W at different intensities during the first week after cessation of daily NO3- supplementation over 3 wk. The results indicate that NO3- supplementation has a long-term effect for at least 7 days after cessation during heavy all-out workloads without affecting endurance capacity.
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Affiliation(s)
- Armin Finkel
- Institute of Sport Medicine, Hannover Medical School , Hannover , Germany.,Institute of Sports Science, Leibniz University Hannover , Hannover , Germany
| | | | - Norbert Maassen
- Institute of Sport Medicine, Hannover Medical School , Hannover , Germany.,Institute of Sports Science, Leibniz University Hannover , Hannover , Germany
| | - Moritz Lützow
- Institute of Sport Medicine, Hannover Medical School , Hannover , Germany
| | - Larissa Sarah Blau
- Institute of Sport Medicine, Hannover Medical School , Hannover , Germany
| | - Erik Hanff
- Institute of Toxicology, Core-Unit, Proteomics, Hannover Medical School , Hannover , Germany
| | - Dimitrios Tsikas
- Institute of Toxicology, Core-Unit, Proteomics, Hannover Medical School , Hannover , Germany
| | - Mirja Maassen
- Institute of Sport Medicine, Hannover Medical School , Hannover , Germany.,Institute of Sports Science, Leibniz University Hannover , Hannover , Germany
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7
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Iannetta D, Okushima D, Inglis EC, Kondo N, Murias JM, Koga S. Blood flow occlusion-related O2 extraction “reserve” is present in different muscles of the quadriceps but greater in deeper regions after ramp-incremental test. J Appl Physiol (1985) 2018; 125:313-319. [DOI: 10.1152/japplphysiol.00154.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
It was recently demonstrated that an O2 extraction reserve, as assessed by the near-infrared spectroscopy (NIRS)-derived deoxygenation signal ([HHb]), exists in the superficial region of vastus lateralis (VL) muscle during an occlusion performed at the end of a ramp-incremental test. However, it is unknown whether this reserve is present and/or different in magnitude in other portions and depths of the quadriceps muscles. We tested the hypothesis that an O2 extraction reserve would exist in other regions of this muscle but is greater in deep compared with more superficial portions. Superficial (VL-s) and deep VL (VL-d) as well as superficial rectus femoris (RF-s) were monitored by a combination of low- and high-power time-resolved (TRS) NIRS. During the occlusion immediately post-ramp-incremental test there was a significant overshoot in the [HHb] signal ( P < 0.05). However, the magnitude of this increase was greater in VL-d (93.2 ± 42.9%) compared with VL-s (55.0 ± 19.6%) and RF-s (47.8 ± 14.0%) ( P < 0.05). The present study demonstrated that an O2 extraction reserve exists in different pools of active muscle fibers of the quadriceps at the end of a ramp exercise to exhaustion. The greater magnitude in the reserve observed in the deeper portion of VL, however, suggests that this portion of muscle may present a greater surplus of oxygenated blood, which is likely due to a greater population of slow-twitch fibers. These findings add to the notion that the plateau in the [HHb] signal toward the end of a ramp-incremental exercise does not indicate the upper limit of O2 extraction. NEW & NOTEWORTHY Different portions of the quadriceps muscles exhibited an untapped O2 extraction reserve during a blood flow occlusion performed at the end of a ramp-incremental exercise. In the deeper portion of the vastus lateralis muscle, this reserve was greater compared with superficial vastus lateralis and rectus femoris. These data suggest that the O2 extraction reserve may be dependent on the vascular and/or oxidative capacities of the muscles.
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Affiliation(s)
- Danilo Iannetta
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | | | | | | | - Juan M Murias
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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Gittemeier EM, Ericson T, Ghosh P, Copp SW, Opoku-Acheampong AB, Behnke BJ. Effects of aging and exercise training on the dynamics of vasoconstriction in skeletal muscle resistance vessels. Eur J Appl Physiol 2017; 117:397-407. [PMID: 28154974 DOI: 10.1007/s00421-017-3541-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 01/09/2017] [Indexed: 11/24/2022]
Abstract
It is unknown whether aging or exercise training affect the dynamics of arteriolar vasoconstriction. PURPOSE We hypothesized that old age will slow, and exercise training will speed, the dynamics of skeletal muscle arteriolar vasoconstriction in resistance vessels of aged rats. METHOD Young (6 month old) and aged (24 month old) male Fischer-344 rats were assigned to sedentary (Sed: n = 6/age group) or exercise-trained (ET: n = 5 aged and 6 young; via treadmill running for 10-12 weeks) groups. After completion of training, arterioles from the red portion of the gastrocnemius muscle were removed, cannulated, and exposed to 10-4 M norepinephrine (NE) or 20 mM caffeine. Changes in luminal diameter were recorded for analysis of constrictor dynamics. RESULT Old age blunted all kinetic parameters (i.e., time delay, time constant) resulting in vasoconstriction taking ~3 times as long to reach a steady state (SS) versus younger counterparts for NE (aged-sed: 15.6 ± 6.0 versus young-sed: 4.6 ± 0.5 s; P < 0.05) with a similar time course to caffeine. Exercise training resulted in a similar time to SS between age groups for NE (aged-ET: 6.8 ± 1.6 versus young-ET: 7.0 ± 0.6 s) and caffeine (aged-ET: 7.8 ± 0.6 versus young-ET: 8.6 ± 1.0 s). CONCLUSION The results of this study demonstrate that aging blunts the rate of vasoconstriction in skeletal muscle resistance vessels to the sympathetic neurotransmitter NE due, in part, to an attenuated rate of contraction from intracellular calcium release. Further, exercise training speeds the dynamics of constriction to both NE and caffeine with old age.
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Affiliation(s)
| | - Tyler Ericson
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
| | - Payal Ghosh
- Department of Food, Nutrition and Exercise Sciences, Florida State University, Tallahassee, FL, USA
| | - Steven W Copp
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
| | | | - Bradley J Behnke
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA. .,Department of Kinesiology, Johnson Cancer Research Center, Kansas State University, Manhattan, KS, 66506, USA.
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Louvaris Z, Habazettl H, Asimakos A, Wagner H, Zakynthinos S, Wagner PD, Vogiatzis I. Heterogeneity of blood flow and metabolism during exercise in patients with chronic obstructive pulmonary disease. Respir Physiol Neurobiol 2017; 237:42-50. [PMID: 28057577 DOI: 10.1016/j.resp.2016.12.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 12/19/2016] [Accepted: 12/28/2016] [Indexed: 11/17/2022]
Abstract
The study investigated whether the capacity to regulate muscle blood flow (Q) relative to metabolic demand (VO2) is impaired in COPD. Using six NIRS optodes over the upper, middle and lower vastus lateralis in 6 patients, (FEV1:46±12%predicted) we recorded from each: a) Q by indocyanine green dye injection, b) VO2/Q ratios based on fractional tissue O2 saturation and c) VO2 as their product, during constant-load exercise (at 20%, 50% and 80% of peak capacity) in normoxia and hyperoxia (FIO2:1.0). At 50 and 80%, relative dispersion (RD) for Q, but not for VO2, was greater in normoxia (0.67±0.07 and 0.79±0.08, respectively) compared to hyperoxia (0.57±0.12 and 0.72±0.07, respectively). In both conditions, RD for VO2 and Q significantly increased throughout exercise; however, RD of VO2/Q ratio was minimal (normoxia: 0.12-0.08 vs hyperoxia: 0.13-0.09). Muscle Q and VO2 appear closely matched in COPD patients, indicating a minimal impact of heterogeneity on muscle oxygen availability at submaximal levels of exercise.
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Affiliation(s)
- Zafeiris Louvaris
- Faculty of Physical Education and Sport Sciences, National and Kapodistrian University of Athens, Greece; 1st Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, "M. Simou, and G.P. Livanos Laboratories", National and Kapodistrian University of Athens, Greece; Faculty of Kinesiology and Rehabilitation Sciences, Division of Respiratory Rehabilitation, Department of Rehabilitation Sciences KU Leuven, University Hospital Leuven, Leuven, Belgium.
| | - Helmut Habazettl
- Institute of Physiology, Charité Campus Benjamin Franklin, Berlin, Germany; Institute of Anesthesiology, Deutsches Herzzentrum Berlin, Germany
| | - Andreas Asimakos
- 1st Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, "M. Simou, and G.P. Livanos Laboratories", National and Kapodistrian University of Athens, Greece
| | - Harrieth Wagner
- Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Spyros Zakynthinos
- 1st Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, "M. Simou, and G.P. Livanos Laboratories", National and Kapodistrian University of Athens, Greece
| | - Peter D Wagner
- Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Ioannis Vogiatzis
- Faculty of Physical Education and Sport Sciences, National and Kapodistrian University of Athens, Greece; 1st Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, "M. Simou, and G.P. Livanos Laboratories", National and Kapodistrian University of Athens, Greece; Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University Newcastle, UK
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Poole DC, Burnley M, Vanhatalo A, Rossiter HB, Jones AM. Critical Power: An Important Fatigue Threshold in Exercise Physiology. Med Sci Sports Exerc 2016; 48:2320-2334. [PMID: 27031742 PMCID: PMC5070974 DOI: 10.1249/mss.0000000000000939] [Citation(s) in RCA: 299] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
: The hyperbolic form of the power-duration relationship is rigorous and highly conserved across species, forms of exercise, and individual muscles/muscle groups. For modalities such as cycling, the relationship resolves to two parameters, the asymptote for power (critical power [CP]) and the so-called W' (work doable above CP), which together predict the tolerable duration of exercise above CP. Crucially, the CP concept integrates sentinel physiological profiles-respiratory, metabolic, and contractile-within a coherent framework that has great scientific and practical utility. Rather than calibrating equivalent exercise intensities relative to metabolically distant parameters such as the lactate threshold or V˙O2max, setting the exercise intensity relative to CP unifies the profile of systemic and intramuscular responses and, if greater than CP, predicts the tolerable duration of exercise until W' is expended, V˙O2max is attained, and intolerance is manifested. CP may be regarded as a "fatigue threshold" in the sense that it separates exercise intensity domains within which the physiological responses to exercise can (CP) be stabilized. The CP concept therefore enables important insights into 1) the principal loci of fatigue development (central vs. peripheral) at different intensities of exercise and 2) mechanisms of cardiovascular and metabolic control and their modulation by factors such as O2 delivery. Practically, the CP concept has great potential application in optimizing athletic training programs and performance as well as improving the life quality for individuals enduring chronic disease.
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Affiliation(s)
- David C. Poole
- Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, Kansas, U.S.A
| | - Mark Burnley
- School of Sport and Exercise Sciences, University of Kent, Chatham, U.K
| | - Anni Vanhatalo
- Sport and Health Sciences, St. Luke’s Campus, University of Exeter, Exeter, U.K
| | - Harry B. Rossiter
- Faculty of Biological Sciences University of Leeds, Leeds, U.K
- Rehabilitaion Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, U.S.A
| | - Andrew M. Jones
- Sport and Health Sciences, St. Luke’s Campus, University of Exeter, Exeter, U.K
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11
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Čebašek V, Ribarič S. Changes in the Capillarity of the Rat Extensor Digitorum Longus Muscle 4 Weeks after Nerve Injury Studied by 2D Measurement Methods. Cells Tissues Organs 2016; 201:211-9. [PMID: 27023720 DOI: 10.1159/000444140] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2016] [Indexed: 11/19/2022] Open
Abstract
We have previously shown by 3D study that 2 weeks after nerve injury there was no change in the length of capillaries per muscle fibre length in rat extensor digitorum longus muscle (EDL). The primary goal of the present 2D study was to determine the capillarity of rat EDL 4 weeks after various modes of nerve injury. Additionally, we wished to calculate the same capillary/fibre parameters that were used in our 3D stereological study. EDL muscles derived from denervated (4 weeks after nerve injury), re-innervated (4 weeks after two successive nerve crushes) and age-matched controls from the beginning (CON-1) and the end (CON-2) of the experiment were analysed in two ways. Global indices of capillarity, such as capillary density (CD) and capillary/fibre (C/F) ratio, were determined by automatic analysis, local indices as the number (CAF) and the length of capillaries around individual muscle fibres (Lcap) in relation to muscle fibre size were estimated manually by tracing the muscle fibre outlines and the transversally and longitudinally cut segments of capillaries seen in 5-µm-thin muscle cross sections. Four weeks after both types of nerve injury, CD increased in comparison to the CON-2 group (p < 0.001) due to atrophied muscle fibres in denervated muscles and probably proliferation of capillaries in re-innervated ones. Higher C/F, CAF (both p < 0.001) and Lcap (p < 0.01) in re-innervated than denervated EDL confirmed this assumption. Calculated capillary/fibre parameters were comparable to our previous 3D study, which strengthens the practical value to the adapted 2D method used in this study.
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Heinonen I, Koga S, Kalliokoski KK, Musch TI, Poole DC. Heterogeneity of Muscle Blood Flow and Metabolism: Influence of Exercise, Aging, and Disease States. Exerc Sport Sci Rev 2015; 43:117-24. [PMID: 25688763 DOI: 10.1249/jes.0000000000000044] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The systematic increase in V˙O2 uptake and O2 extraction with increasing work rates conceals a substantial heterogeneity of O2 delivery (Q˙O2)-to- V˙O2 matching across and within muscles and other organs. We hypothesize that whether increased/decreased Q˙O2/V˙O2 heterogeneity can be judged as "good" or "bad," for example, after exercise training or in aged individuals or with disease (heart failure, diabetes) depends on the resultant effects on O2 transport and contractile performance.
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Affiliation(s)
- Ilkka Heinonen
- 1Turku PET Centre, University of Turku, Turku, Finland; 2Division of Experimental Cardiology, Thoraxcenter, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands; 3School of Sport Science, Exercise and Health, University Of Western Australia, Crawley, Western Australia, Australia; 4Applied Physiology Laboratory, Kobe Design University, Kobe, Japan; and 5Departments of Kinesiology, Anatomy and Physiology, Kansas State University, Manhattan, KS
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Okushima D, Poole DC, Rossiter HB, Barstow TJ, Kondo N, Ohmae E, Koga S. Muscle deoxygenation in the quadriceps during ramp incremental cycling: Deep vs. superficial heterogeneity. J Appl Physiol (1985) 2015; 119:1313-9. [PMID: 26404619 DOI: 10.1152/japplphysiol.00574.2015] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 09/21/2015] [Indexed: 01/31/2023] Open
Abstract
Muscle deoxygenation (i.e., deoxy[Hb + Mb]) during exercise assesses the matching of oxygen delivery (Q̇O2) to oxygen utilization (V̇O2). Until now limitations in near-infrared spectroscopy (NIRS) technology did not permit discrimination of deoxy[Hb + Mb] between superficial and deep muscles. In humans, the deep quadriceps is more highly vascularized and oxidative than the superficial quadriceps. Using high-power time-resolved NIRS, we tested the hypothesis that deoxygenation of the deep quadriceps would be less than in superficial muscle during incremental cycling exercise in eight males. Pulmonary V̇O2 was measured and muscle deoxy[Hb + Mb] was determined in the superficial vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF-s) and the deep rectus femoris (RF-d). deoxy[Hb + Mb] in RF-d was significantly less than VL at 70% (67.2 ± 7.0 vs. 75.5 ± 10.7 μM) and 80% (71.4 ± 11.0 vs. 79.0 ± 15.4 μM) of peak work rate (WR(peak)), but greater than VL and VM at WR(peak) (87.7 ± 32.5 vs. 76.6 ± 17.5 and 75.1 ± 19.9 μM). RF-s was intermediate at WR(peak) (82.6 ± 18.7 μM). Total hemoglobin and myoglobin concentration and tissue oxygen saturation were significantly greater in RF-d than RF-s throughout exercise. The slope of deoxy[Hb + Mb] increase (proportional to Q̇O2/V̇O2) in VL and VM slowed markedly above 70% WR(peak), whereas it became greater in RF-d. This divergent deoxygenation pattern may be due to a greater population of slow-twitch muscle fibers in the RF-d muscle and the differential recruitment profiles and vascular and metabolic control properties of specific fiber populations within superficial and deeper muscle regions.
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Affiliation(s)
- Dai Okushima
- Applied Physiology Laboratory, Kobe Design University, Kobe, Hyogo, Japan
| | - David C Poole
- Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, Kansas
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Center, Division of Respiratory & Critical Care Physiology & Medicine, Los Angeles Biomedical Research Institute at Harbor-University of California Los Angeles Medical Center, Torrance, California
| | - Thomas J Barstow
- Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, Kansas
| | | | | | - Shunsaku Koga
- Applied Physiology Laboratory, Kobe Design University, Kobe, Hyogo, Japan;
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14
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Koga S, Barstow TJ, Okushima D, Rossiter HB, Kondo N, Ohmae E, Poole DC. Validation of a high-power, time-resolved, near-infrared spectroscopy system for measurement of superficial and deep muscle deoxygenation during exercise. J Appl Physiol (1985) 2015; 118:1435-42. [PMID: 25840439 DOI: 10.1152/japplphysiol.01003.2014] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 03/31/2015] [Indexed: 11/22/2022] Open
Abstract
Near-infrared assessment of skeletal muscle is restricted to superficial tissues due to power limitations of spectroscopic systems. We reasoned that understanding of muscle deoxygenation may be improved by simultaneously interrogating deeper tissues. To achieve this, we modified a high-power (∼8 mW), time-resolved, near-infrared spectroscopy system to increase depth penetration. Precision was first validated using a homogenous optical phantom over a range of inter-optode spacings (OS). Coefficients of variation from 10 measurements were minimal (0.5-1.9%) for absorption (μa), reduced scattering, simulated total hemoglobin, and simulated O2 saturation. Second, a dual-layer phantom was constructed to assess depth sensitivity, and the thickness of the superficial layer was varied. With a superficial layer thickness of 1, 2, 3, and 4 cm (μa = 0.149 cm(-1)), the proportional contribution of the deep layer (μa = 0.250 cm(-1)) to total μa was 80.1, 26.9, 3.7, and 0.0%, respectively (at 6-cm OS), validating penetration to ∼3 cm. Implementation of an additional superficial phantom to simulate adipose tissue further reduced depth sensitivity. Finally, superficial and deep muscle spectroscopy was performed in six participants during heavy-intensity cycle exercise. Compared with the superficial rectus femoris, peak deoxygenation of the deep rectus femoris (including the superficial intermedius in some) was not significantly different (deoxyhemoglobin and deoxymyoglobin concentration: 81.3 ± 20.8 vs. 78.3 ± 13.6 μM, P > 0.05), but deoxygenation kinetics were significantly slower (mean response time: 37 ± 10 vs. 65 ± 9 s, P ≤ 0.05). These data validate a high-power, time-resolved, near-infrared spectroscopy system with large OS for measuring the deoxygenation of deep tissues and reveal temporal and spatial disparities in muscle deoxygenation responses to exercise.
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Affiliation(s)
- Shunsaku Koga
- Applied Physiology Laboratory, Kobe Design University, Kobe, Japan;
| | - Thomas J Barstow
- Departments of Anatomy and Physiology and Kinesiology, Kansas State University, Manhattan, Kansas
| | - Dai Okushima
- Applied Physiology Laboratory, Kobe Design University, Kobe, Japan
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Center, Division of Respiratory & Critical Care Physiology & Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California
| | | | | | - David C Poole
- Departments of Anatomy and Physiology and Kinesiology, Kansas State University, Manhattan, Kansas
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15
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Holdsworth CT, Copp SW, Ferguson SK, Sims GE, Poole DC, Musch TI. Acute inhibition of ATP-sensitive K+ channels impairs skeletal muscle vascular control in rats during treadmill exercise. Am J Physiol Heart Circ Physiol 2015; 308:H1434-42. [PMID: 25820394 DOI: 10.1152/ajpheart.00772.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 03/25/2015] [Indexed: 10/23/2022]
Abstract
The ATP-sensitive K(+) (KATP) channel is part of a class of inward rectifier K(+) channels that can link local O2 availability to vasomotor tone across exercise-induced metabolic transients. The present investigation tested the hypothesis that if KATP channels are crucial to exercise hyperemia, then inhibition via glibenclamide (GLI) would lower hindlimb skeletal muscle blood flow (BF) and vascular conductance during treadmill exercise. In 27 adult male Sprague-Dawley rats, mean arterial pressure, blood lactate concentration, and hindlimb muscle BF (radiolabeled microspheres) were determined at rest (n = 6) and during exercise (n = 6-8, 20, 40, and 60 m/min, 5% incline, i.e., ~60-100% maximal O2 uptake) under control and GLI conditions (5 mg/kg intra-arterial). At rest and during exercise, mean arterial pressure was higher (rest: 17 ± 3%, 20 m/min: 5 ± 1%, 40 m/min: 5 ± 2%, and 60 m/min: 5 ± 1%, P < 0.05) with GLI. Hindlimb muscle BF (20 m/min: 16 ± 7%, 40 m/min: 30 ± 9%, and 60 m/min: 20 ± 8%) and vascular conductance (20 m/min: 20 ± 7%, 40 m/min: 33 ± 8%, and 60 m/min: 24 ± 8%) were lower with GLI during exercise at 20, 40, and 60 m/min, respectively (P < 0.05 for all) but not at rest. Within locomotory muscles, there was a greater fractional reduction present in muscles comprised predominantly of type I and type IIa fibers at all exercise speeds (P < 0.05). Additionally, blood lactate concentration was 106 ± 29% and 44 ± 15% higher during exercise with GLI at 20 and 40 m/min, respectively (P < 0.05). That KATP channel inhibition reduces hindlimb muscle BF during exercise in rats supports the obligatory contribution of KATP channels in large muscle mass exercise-induced hyperemia.
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Affiliation(s)
- Clark T Holdsworth
- Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas; and
| | - Steven W Copp
- Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas; and
| | - Scott K Ferguson
- Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas; and
| | - Gabrielle E Sims
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - David C Poole
- Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas; and Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Timothy I Musch
- Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas; and Department of Kinesiology, Kansas State University, Manhattan, Kansas
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16
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Koga S, Rossiter HB, Heinonen I, Musch TI, Poole DC. Dynamic heterogeneity of exercising muscle blood flow and O2 utilization. Med Sci Sports Exerc 2014; 46:860-76. [PMID: 24091989 DOI: 10.1249/mss.0000000000000178] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Resolving the bases for different physiological functioning or exercise performance within a population is dependent on our understanding of control mechanisms. For example, when most young healthy individuals run or cycle at moderate intensities, oxygen uptake (VO2) kinetics are rapid and the amplitude of the VO2 response is not constrained by O2 delivery. For this to occur, muscle O2 delivery (i.e., blood flow × arterial O2 concentration) must be coordinated superbly with muscle O2 requirements (VO2), the efficacy of which may differ among muscles and distinct fiber types. When the O2 transport system succumbs to the predations of aging or disease (emphysema, heart failure, and type 2 diabetes), muscle O2 delivery and O2 delivery-VO2 matching and, therefore, muscle contractile function become impaired. This forces greater influence of the upstream O2 transport pathway on muscle aerobic energy production, and the O2 delivery-VO2 relationship(s) assumes increased importance. This review is the first of its kind to bring a broad range of available techniques, mostly state of the art, including computer modeling, radiolabeled microspheres, positron emission tomography, magnetic resonance imaging, near-infrared spectroscopy, and phosphorescence quenching to resolve the O2 delivery-VO2 relationships and inherent heterogeneities at the whole body, interorgan, muscular, intramuscular, and microvascular/myocyte levels. Emphasis is placed on the following: 1) intact humans and animals as these provide the platform essential for framing and interpreting subsequent investigations, 2) contemporary findings using novel technological approaches to elucidate O2 delivery-VO2 heterogeneities in humans, and 3) future directions for investigating how normal physiological responses can be explained by O2 delivery-VO2 heterogeneities and the impact of aging/disease on these processes.
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Affiliation(s)
- Shunsaku Koga
- 1Applied Physiology Laboratory, Kobe Design University, JAPAN; 2Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, and School of Biomedical Sciences, University of Leeds, Leeds, UNITED KINGDOM; 3Turku PET Centre and Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku and Turku University Hospital, Turku, FINLAND; Division of Experimental Cardiology, Thoraxcenter, Erasmus MC, University Medical Center Rotterdam, Rotterdam, THE NETHERLANDS; and 4Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, KS
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Jendzjowsky NG, Just TP, Jones KE, DeLorey DS. Acute tetrahydrobiopterin supplementation attenuates sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle of healthy rats. Physiol Rep 2014; 2:2/10/e12164. [PMID: 25318748 PMCID: PMC4254091 DOI: 10.14814/phy2.12164] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Tetrahydrobiopterin (BH4) is an essential cofactor for the production of nitric oxide (NO) and supplementation with BH4 improves NO‐dependent vasodilation. NO also reduces sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle. Thus, we hypothesized that supplementation with BH4 would blunt sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle. Sprague‐Dawley rats (n = 15, 399 ± 57 g) were anesthetized and instrumented with an indwelling brachial artery catheter, femoral artery flow probe, and a stimulating electrode on the lumbar sympathetic chain. Triceps surae muscles were stimulated to contract rhythmically at 30% and 60% of maximal contractile force (MCF). The percentage change of femoral vascular conductance (%FVC) in response to sympathetic stimulations delivered at 2 and 5 Hz was determined at rest and during muscle contraction in control and acute BH4 supplementation (20 mg·kg−1 + 10 mg·kg−1·h−1, IA) conditions. BH4 reduced (P < 0.05) the vasoconstrictor response to sympathetic stimulation (i.e., decrease in FVC) at rest (Control: 2 Hz: −28 ± 5%FVC; 5 Hz: −45 ± 5%; BH4: 2 Hz: −17 ± 4%FVC; 5 Hz: −34 ± 7%FVC) and during muscular contraction at 30% MCF (Control: 2 Hz: −14 ± 6%FVC; 5 Hz: −28 ± 11%; BH4: 2 Hz: −6 ± 6%FVC; 5 Hz: −16 ± 10%) and 60% MCF (Control: 2 Hz: −7 ± 3%FVC; 5 Hz: −16 ± 6%FVC; BH4: 2 Hz: −2 ± 3%FVC; 5 Hz: −11 ± 6%FVC). These data are consistent with our hypothesis that acute BH4 supplementation decreases sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle. Tetrahydrobiopterin (BH4) is an essential cofactor for the production of nitric oxide (NO) and NO reduces sympathetic vasoconstrictor responsiveness in the skeletal muscle vascular bed. Thus, we hypothesized that supplementation with BH4 would blunt sympathetic vasoconstrictor responsiveness. The data demonstrate that acute BH4 supplementation decreases sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle.
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Affiliation(s)
- Nicholas G Jendzjowsky
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Timothy P Just
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Kelvin E Jones
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Darren S DeLorey
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
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18
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Kano Y, Miura S, Eshima H, Ezaki O, Poole DC. The effects of PGC-1α on control of microvascular Po2 kinetics following onset of muscle contractions. J Appl Physiol (1985) 2014; 117:163-70. [DOI: 10.1152/japplphysiol.00080.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
During contractions, regulation of microvascular oxygen partial pressure (Pmvo2), which drives blood-myocyte O2 flux, is a function of skeletal muscle fiber type and oxidative capacity and can be altered by exercise training. The kinetics of Pmvo2 during contractions in predominantly fast-twitch muscles evinces a more rapid fall to far lower levels compared with slow-twitch counterparts. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) improves endurance performance, in part, due to mitochondrial biogenesis, a fiber-type switch to oxidative fibers, and angiogenesis in skeletal muscle. We tested the hypothesis that improvement of exercise capacity by genetic overexpression of PGC-1α would be associated with an altered Pmvo2 kinetics profile of the fast-twitch (white) gastrocnemius during contractions toward that seen in slow-twitch muscles (i.e., slowed response kinetics and elevated steady-state Pmvo2). Phosphorescence quenching techniques were used to measure Pmvo2 at rest and during separate bouts of twitch (1 Hz) and tetanic (100 Hz) contractions in gastrocnemius muscles of mice with overexpression of PGC-1α and wild-type littermates (WT) mice under isoflurane anesthesia. Muscles of PGC-1α mice exhibited less fatigue than WT ( P < 0.01). However, except for the Pmvo2 response immediately following onset of contractions, WT and PGC-1α mice demonstrated similar Pmvo2 kinetics. Specifically, the time delay of the Pmvo2 response was shortened in PGC-1α mice compared with WT (1 Hz: WT, 6.6 ± 2.4 s; PGC-1α, 2.9 ± 0.8 s; 100 Hz: WT, 3.3 ± 1.1 s, PGC-1α, 0.9 ± 0.3 s, both P < 0.05). The ratio of muscle force to Pmvo2 was higher for the duration of tetanic contractions in PGC-1α mice. Slower dynamics and maintenance of higher Pmvo2 following muscle contractions is not obligatory for improved fatigue resistance in fast-twitch muscle of PGC-1α mice. Moreover, overexpression of PGC-1α may accelerate O2 utilization kinetics to a greater extent than O2 delivery kinetics.
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Affiliation(s)
- Yutaka Kano
- Department of Engineering Science, University of Electro-Communications, Chofu, Tokyo, Japan
| | - Shinji Miura
- Graduate School of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka, Japan
| | - Hiroaki Eshima
- Department of Engineering Science, University of Electro-Communications, Chofu, Tokyo, Japan
| | - Osamu Ezaki
- Department of Human Health and Design, Showa Women's University, Tokyo, Japan; and
| | - David C. Poole
- Departments of Anatomy, Physiology, and Kinesiology, Kansas State University, Manhattan, Kansas
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Barvitenko NN, Aslam M, Filosa J, Matteucci E, Nikinmaa M, Pantaleo A, Saldanha C, Baskurt OK. Tissue oxygen demand in regulation of the behavior of the cells in the vasculature. Microcirculation 2014; 20:484-501. [PMID: 23441854 DOI: 10.1111/micc.12052] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 02/19/2013] [Indexed: 12/20/2022]
Abstract
The control of arteriolar diameters in microvasculature has been in the focus of studies on mechanisms matching oxygen demand and supply at the tissue level. Functionally, important vascular elements include EC, VSMC, and RBC. Integration of these different cell types into functional units aimed at matching tissue oxygen supply with tissue oxygen demand is only achieved when all these cells can respond to the signals of tissue oxygen demand. Many vasoactive agents that serve as signals of tissue oxygen demand have their receptors on all these types of cells (VSMC, EC, and RBC) implying that there can be a coordinated regulation of their behavior by the tissue oxygen demand. Such functions of RBC as oxygen carrying by Hb, rheology, and release of vasoactive agents are considered. Several common extra- and intracellular signaling pathways that link tissue oxygen demand with control of VSMC contractility, EC permeability, and RBC functioning are discussed.
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20
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Horiuchi M, Fadel PJ, Ogoh S. Differential effect of sympathetic activation on tissue oxygenation in gastrocnemius and soleus muscles during exercise in humans. Exp Physiol 2013; 99:348-58. [PMID: 24163424 DOI: 10.1113/expphysiol.2013.075846] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? The normal ability of sympathetic nerves to cause vasoconstriction is blunted in exercising skeletal muscle, a phenomenon termed 'functional sympatholysis'. Animal studies suggest that functional sympatholysis appears to occur preferentially in fast-twitch type II glycolytic compared with slow-twitch type I oxidative skeletal muscle. We asked whether these findings can be extended to humans. What is the main finding and its importance? We show that skeletal muscles composed largely of fast-twitch type II fibres may also be more sensitive to functional sympatholysis in humans, particularly at lower exercise intensities. Additionally, independent of muscle fibre type composition, the magnitude of sympatholysis is strongly related to exercise-induced increases in metabolic demand. Animal studies suggest that functional sympatholysis appears to occur preferentially in glycolytic (largely type II) compared with oxidative (largely type I) skeletal muscle. Whether these findings can be extended to humans currently remains unclear. In 12 healthy male subjects, vasoconstrictor responses in gastrocnemius (i.e. primarily type II) and soleus muscles (i.e. primarily type I) were measured using near-infrared spectroscopy to detect decreases in muscle oxygenation (HbO(2)) in response to sympathetic activation evoked by a cold pressor test (CPT). The HbO(2) responses to a CPT at rest were compared with responses during steady-state plantar flexion exercise (30 repetitions min(-1)) performed at 10, 20 and 40% maximal voluntary contraction (MVC) for 6 min. In resting conditions, HbO(2) at the gastrocnemius (-14 ± 1%) and soleus muscles (-16 ± 1%) decreased significantly during CPT, with no differences between muscles. During planter flexion at 20% MVC, the change in HbO(2) in response to the CPT was blunted in gastrocnemius but not soleus, whereas during 40% MVC both muscles exhibited a significant attenuation to sympathetic activation. The decreases in HbO(2) in response to the CPT during exercise were significantly correlated with the metabolic demands of exercise (the decreases in HbO(2) in response to steady-state plantar flexion) in both gastrocnemius and soleus muscles. Collectively, these results suggest that skeletal muscles composed mainly of glycolytic type II fibres are more sensitive to functional sympatholysis, particularly at lower intensities of exercise. Moreover, the blunting of sympathetic vasoconstriction during exercise is strongly related to metabolic demand; an effect that appears independent of fibre type composition.
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Affiliation(s)
- Masahiro Horiuchi
- * Department of Biomedical Engineering, Toyo University, Kujirai 2100, Kawagoe City, Saitama 350-8585, Japan.
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Jendzjowsky NG, DeLorey DS. Role of neuronal nitric oxide in the inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle of healthy rats. J Appl Physiol (1985) 2013; 115:97-106. [DOI: 10.1152/japplphysiol.00250.2013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Isoform-specific nitric oxide (NO) synthase (NOS) contributions to NO-mediated inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle are incompletely understood. The purpose of the present study was to investigate the role of neuronal NOS (nNOS) in the inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle of healthy rats. We hypothesized that acute pharmacological inhibition of nNOS would augment sympathetic vasoconstriction in resting and contracting skeletal muscle, demonstrating that nNOS is primarily responsible for NO-mediated inhibition of sympathetic vasoconstriction. Sprague-Dawley rats ( n = 13) were anesthetized and instrumented with an indwelling brachial artery catheter, femoral artery flow probe, and lumbar sympathetic chain stimulating electrodes. Triceps surae muscles were stimulated to contract rhythmically at 60% of maximal contractile force. In series 1 ( n = 9), the percent change in femoral vascular conductance (%FVC) in response to sympathetic stimulations delivered at 2 and 5 Hz was determined at rest and during muscle contraction before and after selective nNOS blockade with S-methyl-l-thiocitrulline (SMTC, 0.6 mg/kg iv) and subsequent nonselective NOS blockade with Nω-nitro-l-arginine methyl ester (l-NAME, 5 mg/kg iv). In series 2 ( n = 4), l-NAME was injected first, and then SMTC was injected to determine if the effect of l-NAME on constrictor responses was influenced by selective nNOS inhibition. Sympathetic stimulation decreased FVC at rest (−25 ± 7 and −44 ± 8%FVC at 2 and 5 Hz, respectively) and during contraction (−7 ± 3 and −19 ± 5%FVC at 2 and 5 Hz, respectively). The decrease in FVC in response to sympathetic stimulation was greater in the presence of SMTC at rest (−32 ± 6 and −49 ± 8%FVC at 2 and 5 Hz, respectively) and during contraction (−21 ± 4 and −28 ± 4%FVC at 2 and 5 Hz, respectively). l-NAME further increased ( P < 0.05) the sympathetic vasoconstrictor response at rest (−47 ± 4 and −60 ± 6%FVC at 2 and 5 Hz, respectively) and during muscle contraction (−33 ± 3 and −40 ± 6%FVC at 2 and 5 Hz, respectively). The effect of l-NAME was not altered by the order of nNOS inhibition. These data demonstrate that NO derived from nNOS and endothelial NOS contribute to the inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle.
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Affiliation(s)
- Nicholas G. Jendzjowsky
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada; and
| | - Darren S. DeLorey
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada; and
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada
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Heinonen I, Wendelin-Saarenhovi M, Kaskinoro K, Knuuti J, Scheinin M, Kalliokoski KK. Inhibition of α-adrenergic tone disturbs the distribution of blood flow in the exercising human limb. Am J Physiol Heart Circ Physiol 2013; 305:H163-72. [PMID: 23666670 DOI: 10.1152/ajpheart.00925.2012] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The role of neuronal regulation of human cardiovascular function remains incompletely elucidated, especially during exercise. Here we, by positron emission tomography, monitored tissue-specific blood flow (BF) changes in nine healthy young men during femoral arterial infusions of norepinephrine (NE) and phentolamine. At rest, the α-adrenoceptor agonist NE reduced BF by ~40%, similarly in muscles (from 3.2 ± 1.9 to 1.4 ± 0.3 ml·min(-1)·100 g(-1) in quadriceps femoris muscle), bone (from 1.1 ± 0.4 to 0.5 ± 0.2 ml·min(-1)·100 g(-1)) and adipose tissue (AT) (from 1.2 ± 0.7 to 0.7 ± 0.3 ml·min(-1)·100 g(-1)). During exercise, NE reduced exercising muscle BF by ~16%. BF in AT was reduced similarly as rest. The α-adrenoceptor antagonist phentolamine increased BF similarly in the different muscles and other tissues of the limb at rest. During exercise, BF in inactive muscle was increased 3.4-fold by phentolamine compared with exercise without drug, but BF in exercising muscles was not influenced. Bone and AT (P = 0.055) BF were also increased by phentolamine in the exercise condition. NE increased and phentolamine decreased oxygen extraction in the limb during exercise. We conclude that inhibition of α-adrenergic tone markedly disturbs the distribution of BF and oxygen extraction in the exercising human limb by increasing BF especially around inactive muscle fibers. Moreover, although marked functional sympatholysis also occurs during exercise, the arterial NE infusion that mimics the exaggerated sympathetic nerve activity commonly seen in patients with cardiovascular disease was still capable of directly limiting BF in the exercising leg muscles.
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Affiliation(s)
- Ilkka Heinonen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland.
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23
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Modeling intercellular transfer of biomolecules through tunneling nanotubes. Bull Math Biol 2013; 75:1400-16. [PMID: 23417627 DOI: 10.1007/s11538-013-9819-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2012] [Accepted: 01/21/2013] [Indexed: 10/27/2022]
Abstract
Tunneling nanotubes (TNTs) have previosly been observed as long and thin transient structures forming between cells and intercellular protein transfer through them has been experimentally verified. It is hypothesized that this may be a physiologically important means of cell-cell communication. This paper attempts to give a simple model for the rates of transfer of molecules across these TNTs at different distances. We describe the transfer of both cytosolic and membrane bound molecules between neighboring populations of cells and argue how the lifetime of the TNT, the diffusion rate, distance between cells, and the size of the molecules may affect their transfer. The model described makes certain predictions and opens a number of questions to be explored experimentally.
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Sindler AL, Reyes R, Chen B, Ghosh P, Gurovich AN, Kang LS, Cardounel AJ, Delp MD, Muller-Delp JM. Age and exercise training alter signaling through reactive oxygen species in the endothelium of skeletal muscle arterioles. J Appl Physiol (1985) 2013; 114:681-93. [PMID: 23288555 DOI: 10.1152/japplphysiol.00341.2012] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exercise training ameliorates age-related impairments in endothelium-dependent vasodilation in skeletal muscle arterioles. Additionally, exercise training is associated with increased superoxide production. The purpose of this study was to determine the role of superoxide and superoxide-derived reactive oxygen species (ROS) signaling in mediating endothelium-dependent vasodilation of soleus muscle resistance arterioles from young and old, sedentary and exercise-trained rats. Young (3 mo) and old (22 mo) male rats were either exercise trained or remained sedentary for 10 wk. To determine the impact of ROS signaling on endothelium-dependent vasodilation, responses to acetylcholine were studied under control conditions and during the scavenging of superoxide and/or hydrogen peroxide. To determine the impact of NADPH oxidase-derived ROS, endothelium-dependent vasodilation was determined following NADPH oxidase inhibition. Reactivity to superoxide and hydrogen peroxide was also determined. Tempol, a scavenger of superoxide, and inhibitors of NADPH oxidase reduced endothelium-dependent vasodilation in all groups. Similarly, treatment with catalase and simultaneous treatment with tempol and catalase reduced endothelium-dependent vasodilation in all groups. Decomposition of peroxynitrite also reduced endothelium-dependent vasodilation. Aging had no effect on arteriolar protein content of SOD-1, catalase, or glutathione peroxidase-1; however, exercise training increased protein content of SOD-1 in young and old rats, catalase in young rats, and glutathione peroxidase-1 in old rats. These data indicate that ROS signaling is necessary for endothelium-dependent vasodilation in soleus muscle arterioles, and that exercise training-induced enhancement of endothelial function occurs, in part, through an increase in ROS signaling.
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Affiliation(s)
- Amy L Sindler
- Department of Physiology and Pharmacology, and the Center for Interdisciplinary Research in Cardiovascular Sciences, West Virginia University School of Medicine, Morgantown, West Virginia, USA
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25
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Ferguson SK, Hirai DM, Copp SW, Holdsworth CT, Allen JD, Jones AM, Musch TI, Poole DC. Impact of dietary nitrate supplementation via beetroot juice on exercising muscle vascular control in rats. J Physiol 2012; 591:547-57. [PMID: 23070702 DOI: 10.1113/jphysiol.2012.243121] [Citation(s) in RCA: 218] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Dietary nitrate (NO(3)(-)) supplementation, via its reduction to nitrite (NO(2)(-)) and subsequent conversion to nitric oxide (NO) and other reactive nitrogen intermediates, reduces blood pressure and the O(2) cost of submaximal exercise in humans. Despite these observations, the effects of dietary NO(3)(-) supplementation on skeletal muscle vascular control during locomotory exercise remain unknown. We tested the hypotheses that dietary NO(3)(-) supplementation via beetroot juice (BR) would reduce mean arterial pressure (MAP) and increase hindlimb muscle blood flow in the exercising rat. Male Sprague-Dawley rats (3-6 months) were administered either NO(3)(-) (via beetroot juice; 1 mmol kg(-1) day(-1), BR n = 8) or untreated (control, n = 11) tap water for 5 days. MAP and hindlimb skeletal muscle blood flow and vascular conductance (radiolabelled microsphere infusions) were measured during submaximal treadmill running (20 m min(-1), 5% grade). BR resulted in significantly lower exercising MAP (control: 137 ± 3, BR: 127 ± 4 mmHg, P < 0.05) and blood [lactate] (control: 2.6 ± 0.3, BR: 1.9 ± 0.2 mm, P < 0.05) compared to control. Total exercising hindlimb skeletal muscle blood flow (control: 108 ± 8, BR: 150 ± 11 ml min(-1) (100 g)(-1), P < 0.05) and vascular conductance (control: 0.78 ± 0.05, BR: 1.16 ± 0.10 ml min(-1) (100 g)(-1) mmHg(-1), P < 0.05) were greater in rats that received BR compared to control. The relative differences in blood flow and vascular conductance for the 28 individual hindlimb muscles and muscle parts correlated positively with their percentage type IIb + d/x muscle fibres (blood flow: r = 0.74, vascular conductance: r = 0.71, P < 0.01 for both). These data support the hypothesis that NO(3)(-) supplementation improves vascular control and elevates skeletal muscle O(2) delivery during exercise predominantly in fast-twitch type II muscles, and provide a potential mechanism by which NO(3)(-) supplementation improves metabolic control.
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Affiliation(s)
- Scott K Ferguson
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS 66506, USA
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26
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Cardiovascular side-effects of antipsychotic drugs: The role of the autonomic nervous system. Pharmacol Ther 2012; 135:113-22. [DOI: 10.1016/j.pharmthera.2012.04.003] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 04/08/2012] [Indexed: 01/27/2023]
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Jendzjowsky NG, DeLorey DS. Short-term exercise training augments sympathetic vasoconstrictor responsiveness and endothelium-dependent vasodilation in resting skeletal muscle. Am J Physiol Regul Integr Comp Physiol 2012; 303:R332-9. [DOI: 10.1152/ajpregu.00053.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested the hypotheses that 4 wk of exercise training would diminish the magnitude of vasoconstriction in response to sympathetic nerve stimulation and augment endothelium-dependent vasodilation (EDD) in resting skeletal muscle in a training intensity-dependent manner. Sprague-Dawley rats were randomly assigned to sedentary time-control (S), mild- (M; 20 m/min, 5% grade), or heavy-intensity (H; 40 m/min, 5% grade) treadmill exercise groups. Animals trained 5 days/wk for 4 wk with training volume matched between groups. Rats were anesthetized and instrumented for study 24 h after the last training session. Arterial pressure and femoral artery blood flow were measured, and femoral vascular conductance (FVC) was calculated. Lumbar sympathetic chain stimulation was delivered continuously at 2 Hz and in patterns at 20 and 40 Hz. EDD was assessed by the vascular response to intra-arterial bolus injections of ACh. The response (% change FVC) to sympathetic stimulation increased ( P < 0.05) in a training intensity-dependent manner at 2 Hz (S: −20.2 ± 9.8%, M: −34.0 ± 6.7%, and H: −44.9 ± 2.0%), 20 Hz (S: −22.0 ± 10.6%, M: −31.2 ± 8.4%, and H: −42.8 ± 5.9%), and 40 Hz (S: H −24.5 ± 8.5%, M: −35.1 ± 8.9%, H: −44.9 ± 6.5%). The magnitude of EDD also increased in a training intensity-dependent manner ( P < 0.05). These data demonstrate that short-term exercise training augments the magnitude of vasoconstriction in response to sympathetic stimulation and EDD in resting skeletal muscle in a training intensity-dependent manner.
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Affiliation(s)
- Nicholas G. Jendzjowsky
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada; and
| | - Darren S. DeLorey
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada; and
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada
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McDonough P, Padilla DJ, Kano Y, Musch TI, Poole DC, Behnke BJ. Plasticity of microvascular oxygenation control in rat fast-twitch muscle: effects of experimental creatine depletion. Respir Physiol Neurobiol 2012; 181:14-20. [PMID: 22285799 PMCID: PMC3296908 DOI: 10.1016/j.resp.2012.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2011] [Revised: 01/09/2012] [Accepted: 01/10/2012] [Indexed: 10/14/2022]
Abstract
Aging, heart failure and diabetes each compromise the matching of O2 delivery (Q˙O2)-to-metabolic requirements (O2 uptake, V˙O2) in skeletal muscle such that the O2 pressure driving blood-myocyte O2 flux (microvascular PO2, PmvO2) is reduced and contractile function impaired. In contrast, β-guanidinopropionic acid (β-GPA) treatment improves muscle contractile function, primarily in fast-twitch muscle (Moerland and Kushmerick, 1994). We tested the hypothesis that β-GPA (2% wt/BW in rat chow, 8 weeks; n=14) would improve Q˙O2-to-V˙O2 matching (elevated PmvO2) during contractions (4.5V @ 1Hz) in mixed (MG) and white (WG) portions of the gastrocnemius, both predominantly fast-twitch). Compared with control (CON), during contractions PmvO2 fell less following β-GPA (MG -54%, WG -26%, P<0.05), elevating steady-state PmvO2 (CON, MG: 10±2, WG: 9±1; β-GPA, MG 16±2, WG 18±2 mmHg, P<0.05). This reflected an increased Q˙O2/V˙O2 ratio due primarily to a reduced V˙O2 in β-GPA muscles. It is likely that this adaptation helps facilitate the β-GPA-induced enhancement of contractile function in fast-twitch muscles.
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Affiliation(s)
- Paul McDonough
- Department of Kinesiology, University of Texas at Arlington, Arlington, TX 76019, USA
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Delorey DS, Clifford PS, Mittelstadt S, Anton MM, Kluess HA, Tune JD, Dincer UD, Buckwalter JB. The effect of aging on adrenergic and nonadrenergic receptor expression and responsiveness in canine skeletal muscle. J Appl Physiol (1985) 2011; 112:841-8. [PMID: 22194325 DOI: 10.1152/japplphysiol.00945.2011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We tested the hypothesis that adrenergic and nonadrenergic receptor responsiveness and protein expression would be altered with advancing age. Young (n = 6; 22 ± 1 mo; mean ± SE) and old (n = 6; 118 ± 9 mo) beagles were instrumented with flow probes and an indwelling catheter for continuous measurement of external iliac blood flow and arterial blood pressure. Vascular conductance (VC) was calculated as hindlimb blood flow/mean arterial pressure. Selective agonists for α-1, α-2, neuropeptide-Y (NPY), and purinergic (P2X) receptors were infused at rest and during treadmill running at moderate (2.5 mph) and heavy (4 mph with 2.5% grade) exercise intensities. Feed arteries were dissected from gracilis muscles, and α-1D, α-1B, α-2A, P2X-4, P2X-1, and NPY-Y1 receptor protein expression was determined. Phenylephrine produced similar decreases (P > 0.05) in VC in young and old beagles at rest (young: -62 ± 5%; old: -59 ± 5%) and during moderate (young: -67 ± 5%; old: -62 ± 4%) and heavy (young: -54 ± 4%; old: -49 ± 3%) exercise. Clonidine caused similar (P > 0.05) decreases in VC in old compared with young dogs at rest (young: -59 ± 8%; old: -70 ± 6%) and during moderate (young: -52 ± 6%; old: -47 ± 5%)- and heavy (young: -42 ± 5%; old: -43 ± 5%)-intensity exercise. NPY infusion resulted in a similar decline in VC in young and old beagles at rest (young: -40 ± 7%; old: -39 ± 9%) and during moderate (young: -47 ± 6%; old: -40 ± 6%)- and heavy (young: -40 ± 3%; old: -38 ± 4%)-intensity exercise. α-β-Methylene-ATP also produced similar decreases in VC in young and old beagles at rest (young: -36 ± 6%; old: -40 ± 8%) and during exercise at moderate (young: -42 ± 5%; old: -40 ± 9%) and heavy (young: -47 ± 5%; old: -42 ± 8%) intensities. α-1B receptor protein expression was elevated (P < 0.05) in old compared with young dogs, whereas there were no age-related differences in α-1D or α-2A receptor expression and nonadrenergic P2X-4, P2X-1, and NPY-Y1 receptor expression. The present findings indicate that postsynaptic adrenergic and nonadrenergic receptor responsiveness was not altered by advancing age. Moreover, the expression of adrenergic and nonadrenergic receptors in skeletal-muscle feed arteries was largely unaffected by aging.
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Affiliation(s)
- D S Delorey
- Department of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada.
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