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Meneses AL, Nam MCY, Bailey TG, Anstey C, Golledge J, Keske MA, Greaves K, Askew CD. Skeletal muscle microvascular perfusion responses to cuff occlusion and submaximal exercise assessed by contrast-enhanced ultrasound: The effect of age. Physiol Rep 2021; 8:e14580. [PMID: 33038050 PMCID: PMC7547535 DOI: 10.14814/phy2.14580] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 08/22/2020] [Accepted: 08/28/2020] [Indexed: 11/24/2022] Open
Abstract
Impairments in skeletal muscle microvascular function are frequently reported in patients with various cardiometabolic conditions for which older age is a risk factor. Whether aging per se predisposes the skeletal muscle to microvascular dysfunction is unclear. We used contrast‐enhanced ultrasound (CEU) to compare skeletal muscle microvascular perfusion responses to cuff occlusion and leg exercise between healthy young (n = 12, 26 ± 3 years) and older (n = 12, 68 ± 7 years) adults. Test–retest reliability of CEU perfusion parameters was also assessed. Microvascular perfusion (microvascular volume × flow velocity) of the medial gastrocnemius muscle was measured before and immediately after: (a) 5‐min of thigh‐cuff occlusion, and (b) 5‐min of submaximal intermittent isometric plantar‐flexion exercise (400 N) using CEU. Whole‐leg blood flow was measured using strain‐gauge plethysmography. Repeated measures were obtained with a 15‐min interval, and averaged responses were used for comparisons between age groups. There were no differences in post‐occlusion whole‐leg blood flow and muscle microvascular perfusion between young and older participants (p > .05). Similarly, total whole‐leg blood flow during exercise and post‐exercise peak muscle microvascular perfusion did not differ between groups (p > .05). The overall level of agreement between the test–retest measures of calf muscle perfusion was excellent for measurements taken at rest (intraclass correlation coefficient [ICC] 0.85), and in response to cuff occlusion (ICC 0.89) and exercise (ICC 0.95). Our findings suggest that healthy aging does not affect muscle perfusion responses to cuff‐occlusion and submaximal leg exercise. CEU muscle perfusion parameters measured in response to these provocation tests are highly reproducible in both young and older adults.
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Affiliation(s)
- Annelise L Meneses
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Maroochydore, QLD, Australia
| | - Michael C Y Nam
- Department of Cardiology, Sunshine Coast University Hospital, Birtinya, QLD, Australia
| | - Tom G Bailey
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Maroochydore, QLD, Australia.,Centre for Research on Exercise, Physical Activity and Health, School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Chris Anstey
- Department of Intensive Care, Sunshine Coast University Hospital, Birtinya, QLD, Australia
| | - Jonathan Golledge
- Queensland Research Centre for Peripheral Vascular Disease, College of Medicine and Dentistry, James Cook University, Townsville, QLD, Australia.,Department of Vascular and Endovascular Surgery, The Townsville Hospital, Townsville, QLD, Australia
| | - Michelle A Keske
- School of Exercise and Nutrition Sciences, Institute for Physical Activity and Nutrition, Deakin University, Geelong, VIC, Australia
| | - Kim Greaves
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Maroochydore, QLD, Australia.,Department of Cardiology, Sunshine Coast University Hospital, Birtinya, QLD, Australia
| | - Christopher D Askew
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Maroochydore, QLD, Australia.,Sunshine Coast Health Institute, Sunshine Coast Hospital and Health Service, Birtinya, QLD, Australia
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Lew LA, Liu KR, Pyke KE. Reliability of the hyperaemic response to passive leg movement in young, healthy women. Exp Physiol 2021; 106:2013-2023. [PMID: 34216162 DOI: 10.1113/ep089629] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 07/01/2021] [Indexed: 12/22/2022]
Abstract
NEW FINDINGS What is the central question of this study? This is the first study to assess the day-to-day reliability of passive leg movement-induced hyperaemia (PLM-H), an index of lower-limb microvascular function, in young, healthy women. What is the main finding and its importance? Passive leg movement-induced hyperaemia demonstrated good day-to-day reliability, comparable to other common indices of endothelial function, supporting the use of PLM-H to assess lower-limb microvascular function in women. ABSTRACT Passive leg movement-elicited hyperaemia (PLM-H) provides an index of lower-limb microvascular function. However, there is currently limited information regarding the reliability of PLM-H and no reliability information specific to women. The purpose of this study was to determine the reliability of PLM-H in women on two separate days. Seventeen young, healthy women [22 ± 3 years old (mean ± SD)] participated in two identical visits including three trials of PLM. Using duplex ultrasound, PLM-H was characterized by six indices: peak leg blood flow (LBF) and vascular conductance (LVC), peak change above baseline (Δpeak) for LBF and LVC, and area under the curve above baseline (AUC) during the first 60 s of PLM for LBF and LVC. The results demonstrated good day-to-day reliability of PLM-H characterized as peak LBF [r = 0.84, P < 0.001; intraclass correlation coefficient (ICC) = 0.84; coefficient of variation (CV) = 13.2%], peak LVC (r = 0.82, P < 0.001; ICC = 0.79; CV = 14.4%), Δpeak LBF (r = 0.83, P < 0.001; ICC = 0.82; CV = 17.8%) and Δpeak LVC (r = 0.83, P < 0.001; ICC = 0.80; CV = 16.5%). Characterization of PLM as AUC demonstrated moderate day-to-day reliability: AUC LBF (r = 0.71, P < 0.05; ICC = 0.70; CV = 31.2%) and AUC LVC (r = 0.78, P < 0.001; ICC = 0.74; CV = 27.1%). In conclusion, this study demonstrates that PLM-H has good reliability as an index of microvascular function; however, characterization of PLM-H as peak, Δpeak LBF and LVC is more reliable than AUC.
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Affiliation(s)
- Lindsay A Lew
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - Kaitlyn R Liu
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - Kyra E Pyke
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
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Walker MA, Bailey TG, McIlvenna L, Allen JD, Green DJ, Askew CD. Acute Dietary Nitrate Supplementation Improves Flow Mediated Dilatation of the Superficial Femoral Artery in Healthy Older Males. Nutrients 2019; 11:E954. [PMID: 31035478 PMCID: PMC6566150 DOI: 10.3390/nu11050954] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 04/18/2019] [Accepted: 04/24/2019] [Indexed: 12/15/2022] Open
Abstract
Aging is often associated with reduced leg blood flow, increased arterial stiffness, and endothelial dysfunction, all of which are related to declining nitric oxide (NO) bioavailability. Flow mediated dilatation (FMD) and passive leg movement (PLM) hyperaemia are two techniques used to measure NO-dependent vascular function. We hypothesised that acute dietary nitrate (NO3-) supplementation would improve NO bioavailability, leg FMD, and PLM hyperaemia. Fifteen healthy older men (69 ± 4 years) attended two experiment sessions and consumed either 140 mL of concentrated beetroot juice (800 mg NO3-) or placebo (NO3--depleted beetroot juice) in a randomised, double blind, cross-over design study. Plasma nitrite (NO2-) and NO3-, blood pressure (BP), augmentation index (AIx75), pulse wave velocity (PWV), FMD of the superficial femoral artery, and PLM hyperaemia were measured immediately before and 2.5 h after consuming NO3- and placebo. Placebo had no effect but NO3- led to an 8.6-fold increase in plasma NO2-, which was accompanied by an increase in FMD (NO3-: +1.18 ± 0.94% vs. placebo: 0.23 ± 1.13%, p = 0.002), and a reduction in AIx75 (NO3-: -8.7 ± 11.6% vs. placebo: -4.6 ± 5.5%, p = 0.027). PLM hyperaemia, BP, and PWV were unchanged during both trials. This study showed that a dose of dietary NO3- improved NO bioavailability and enhanced endothelial function as measured by femoral artery FMD. These findings provide insight into the specific central and peripheral vascular responses to dietary NO3- supplementation in older adults.
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Affiliation(s)
- Meegan A Walker
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Sippy Downs, QLD 4556, Australia.
| | - Tom G Bailey
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Sippy Downs, QLD 4556, Australia.
- School of Human Movement and Nutrition Sciences, University of Queensland, St Lucia, QLD 4072, Australia.
| | - Luke McIlvenna
- Institute for Health and Sport, College of Sport and Exercise Science, Victoria University, Melbourne, VIC 3031, Australia.
| | - Jason D Allen
- Institute for Health and Sport, College of Sport and Exercise Science, Victoria University, Melbourne, VIC 3031, Australia.
- Department of Kinesiology, University of Virginia, Charlottesville, VA 22903, USA.
| | - Daniel J Green
- School of Sport Sciences, Exercise and Health, University of Western Australia, West Perth, WA 6872, Australia.
| | - Christopher D Askew
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Sippy Downs, QLD 4556, Australia.
- Sunshine Coast Health Institute, Sunshine Coast Hospital and Health Service, Birtinya, QLD 4575, Australia.
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INDICATORS OF THIGH RHEOGRAM IN PRACTICALLY HEALTHY YOUNG MEN AND YOUNG WOMEN OF DIFFERENT SOMATOTYPES. WORLD OF MEDICINE AND BIOLOGY 2019. [DOI: 10.26724/2079-8334-2019-3-69-55-59] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Groot HJ, Rossman MJ, Garten RS, Wang E, Hoff J, Helgerud J, Richardson RS. The Effect of Physical Activity on Passive Leg Movement-Induced Vasodilation with Age. Med Sci Sports Exerc 2017; 48:1548-57. [PMID: 27031748 DOI: 10.1249/mss.0000000000000936] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
INTRODUCTION Because of reduced nitric oxide (NO) bioavailability with age, passive leg movement (PLM)-induced vasodilation is attenuated in older sedentary subjects and, unlike the young subjects, cannot be augmented by posture-induced elevations in femoral perfusion pressure. However, whether vasodilator function assessed with PLM, and therefore NO bioavailability, is preserved in older individuals with greater physical activity and fitness is unknown. METHODS PLM was performed on four subject groups: young sedentary (Y, 23 ± 1 yr, n = 12), old sedentary (OS, 73 ± 2 yr, n = 12), old active (OA, 71 ± 2 yr, n = 10), and old endurance trained (OT, 72 ± 1 yr, n = 10) in the supine and upright-seated posture. Hemodynamics were measured using ultrasound Doppler and finger photoplethysmography. RESULTS In the supine posture, PLM-induced peak change in leg vascular conductance was significantly attenuated in the OS compared with the young subjects (OS = 4.9 ± 0.5, Y = 6.9 ± 0.7 mL·min·mm Hg) but was not different from the young in the OA and OT (OA = 5.9 ± 1.0, OT = 5.4 ± 0.4 mL·min·mm Hg). The upright-seated posture significantly augmented peak change in leg vascular conductance in all but the OS (OS = 4.9 ± 0.5, Y = 11.8 ± 1.3, OA = 7.3 ± 0.8, OT = 8.1 ± 0.8 mL·min·mm Hg), revealing a significant vasodilatory reserve capacity in the other groups (Y = 4.92 ± 1.18, OA = 1.37 ± 0.55, OT = 2.76 ± 0.95 mL·min·mm Hg). CONCLUSIONS As PLM predominantly reflects NO-mediated vasodilation, these findings support the idea that augmenting physical activity and fitness can protect NO bioavailability, attenuating the deleterious effects of advancing age on vascular function.
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Affiliation(s)
- H Jonathan Groot
- 1Geriatric Research, Education, and Clinical Center Salt Lake City VAMC, UT; 2Department of Exercise and Sport Science University of Utah, Salt Lake City, UT; 3Department of Kinesiology and Health Sciences, Virginia Commonwealth University, Richmond, VA; 4Department of Internal Medicine, University of Utah, Salt Lake City, UT; 5Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, NORWAY; 6Department of Physical Medicine and Rehabilitation, St. Olavs University Hospital, Trondheim, NORWAY; 7Hokksund Medical Rehabilitation Center, Hokksund, NORWAY; and 8Department of Sports and Outdoor Life Studies, Telemark University College, Bø, NORWAY
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Groot HJ, Trinity JD, Layec G, Rossman MJ, Ives SJ, Morgan DE, Bledsoe A, Richardson RS. The role of nitric oxide in passive leg movement-induced vasodilatation with age: insight from alterations in femoral perfusion pressure. J Physiol 2015; 593:3917-28. [PMID: 26108562 DOI: 10.1113/jp270195] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 06/09/2015] [Indexed: 11/08/2022] Open
Abstract
The passive leg movement (PLM) model is a novel approach to assess vascular function. Increasing femoral perfusion pressure (FPP) by moving from the supine to the upright-seated posture augments the vasodilatory response to PLM in the young, with no effect in the old, but whether this augmented vasodilatation is nitric oxide (NO) dependent is unknown. Using an intra-arterial infusion of N(G) -monomethyl-L -arginine (L -NMMA) to inhibit nitric oxide synthase (NOS), the posture-induced increases in the PLM responses in the young were nearly ablated, with no effect of NOS inhibition in the old. Therefore, PLM in combination with alterations in posture can be used to determine changes in NO-mediated vasodilatation with age, and thus, may be a clinically useful tool for assessing NO bioavailability across the human lifespan. We sought to better understand the contribution of nitric oxide (NO) to passive leg movement (PLM)-induced vasodilatation with age, with and without a posture-induced increase in femoral perfusion pressure (FPP). PLM was performed in eight young (24 ± 1 years) and eight old (74 ± 3 years) healthy males, with and without NO synthase inhibition via intra-arterial infusion of N(G) -monomethyl-L -arginine (L -NMMA) into the common femoral artery in both the supine and upright-seated posture. Central and peripheral haemodynamic responses were determined second-by-second with finger photoplethysmography and Doppler ultrasound, respectively. PLM-induced increases in heart rate, stroke volume, cardiac output and reductions in mean arterial pressure were similar between age groups and conditions. In the young, L -NMMA attenuated the peak change in leg vascular conductance (ΔLVCpeak ) in both the supine (control: 7.4 ± 0.9; L -NMMA: 5.2 ± 1.1 ml min(-1) mmHg(-1) , P < 0.05) and upright-seated (control: 12.3 ± 2.0; L -NMMA: 6.4 ± 1.0 ml min(-1) mmHg(-1) , P < 0.05) posture, with no significant change in the old (supine control: 4.2 ± 1.3; supine L -NMMA: 3.4 ± 0.8; upright-seated control: 4.5 ± 0.8; upright-seated L -NMMA: 3.4 ± 0.8 ml min(-1) mmHg(-1) , P > 0.05). Increased FPP augmented the ΔLVCpeak in the young control condition only (P < 0.05). In the upright-seated posture, NOS inhibition attenuated the FPP-induced augmentation of rapid vasodilatation in the young (control: 1.25 ± 0.23; L -NMMA: 0.74 ± 0.11 ml min(-1) mmHg(-1) s(-1) ; P < 0.05), but not the old (control: 0.37 ± 0.07; L -NMMA: 0.25 ± 0.07 ml ml min(-1) mmHg(-1) s(-1) ; P > 0.05). These data reveal that greater FPP increases the role of NO in PLM-induced vasodilatation in the young, but not the old, due to reduced NO bioavailability with age. Therefore, PLM involving alterations in posture may be useful to determine changes in NO bioavailability with age.
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Affiliation(s)
- H Jonathan Groot
- Geriatric Research, Education, and Clinical Centre, VAMC, Salt Lake City, UT, USA.,Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, USA
| | - Joel D Trinity
- Geriatric Research, Education, and Clinical Centre, VAMC, Salt Lake City, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
| | - Gwenael Layec
- Geriatric Research, Education, and Clinical Centre, VAMC, Salt Lake City, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
| | - Matthew J Rossman
- Geriatric Research, Education, and Clinical Centre, VAMC, Salt Lake City, UT, USA.,Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, USA
| | - Stephen J Ives
- Health and Exercise Sciences Department, Skidmore College, Saratoga Springs, NY, USA
| | - David E Morgan
- Department of Anesthesia, University of Utah, Salt Lake City, UT, USA
| | - Amber Bledsoe
- Department of Anesthesia, University of Utah, Salt Lake City, UT, USA
| | - Russell S Richardson
- Geriatric Research, Education, and Clinical Centre, VAMC, Salt Lake City, UT, USA.,Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
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Limberg JK, Johansson RE, McBride PE, Schrage WG. Increased leg blood flow and improved femoral artery shear patterns in metabolic syndrome after a diet and exercise programme. Clin Physiol Funct Imaging 2013; 34:282-9. [PMID: 24237709 DOI: 10.1111/cpf.12095] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 10/01/2013] [Indexed: 01/10/2023]
Abstract
BACKGROUND Altered vascular shear profiles may contribute to the development of atherosclerosis. Physical activity promotes anti-atherogenic shear patterns, resulting in reduced cardiovascular disease risk. Adults with metabolic syndrome (MetSyn) are at increased risk of developing atherosclerosis and cardiovascular disease. Thus, we hypothesized that conduit artery antegrade shear rate (ASR) would increase and retrograde shear rate (RSR) and oscillatory shear indices (OSI) would decrease in MetSyn patients (n = 16, 51 ± 2 years) after participation in a diet and exercise programme (DEP). METHODS Blood flow (Doppler ultrasound, brachial and femoral arteries) was measured, and shear rates were calculated in MetSyn patients before and after 12 weeks of DEP participation. In addition, plasma samples were collected to measure atherogenic markers. RESULTS Diet and exercise programme participation increased resting leg blood flow and femoral artery ASR (P ≤ 0·05), and tended to decrease OSI (P = 0·09); RSR did not change (P>0·05). No changes in resting arm blood flow or ASR were observed (P>0·05), and both RSR and OSI increased after participation (P≤0·05). DEP participation reduced plasma vascular cell adhesion molecule(VCAM)-1 (P = 0·03), with a trend for reduced intercellular cell adhesion molecule(ICAM)-1 (P = 0·09) (i.e. atherogenic markers). CONCLUSION Modest changes in diet and physical activity result in limb-specific improvements in vascular shear profiles and reduced systemic markers of atherosclerotic risk in MetSyn patients. These data provide novel physiologic insight into adaptations that may limit the progression of atherosclerosis in patients with MetSyn.
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Affiliation(s)
- Jacqueline K Limberg
- Department of Kinesiology, School of Education, University of Wisconsin - Madison, Madison, WI, USA
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Groot HJ, Trinity JD, Layec G, Rossman MJ, Ives SJ, Richardson RS. Perfusion pressure and movement-induced hyperemia: evidence of limited vascular function and vasodilatory reserve with age. Am J Physiol Heart Circ Physiol 2012; 304:H610-9. [PMID: 23262136 DOI: 10.1152/ajpheart.00656.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To better understand the mechanisms contributing to reduced blood flow with age, this study sought to elucidate the impact of altered femoral perfusion pressure (FPP) on movement-induced hyperemia. Passive leg movement was performed in 10 young (22 ± 1 yr) and 12 old (72 ± 2 yr) healthy men for 2 min, with and without a posture-induced change in FPP (~7 ± 1 ΔmmHg). Second-by-second measurements of central and peripheral hemodynamic responses were acquired noninvasively (finger photoplethysmography and Doppler ultrasound, respectively), with FPP confirmed in a subset of four young and four old subjects with arterial and venous catheters. Central hemodynamic responses (heart rate, stroke volume, cardiac output, mean arterial pressure) were not affected by age or position. The young exhibited a ~70% greater movement-induced peak change in leg blood flow (ΔLBF(peak)) in the upright-seated posture (supine: 596±68 ml/min; upright: 1,026 ± 85 ml/min). However, in the old the posture change did not alter ΔLBF(peak) (supine: 417±42 ml/min; upright: 412±56 ml/min), despite the similar increases in FPP. Similarly, movement-induced peak change in leg vascular conductance was ~80% greater for the young in the upright-seated posture (supine: 7.1 ± 0.8 ml·min(-1)·mmHg(-1); upright: 12.8 ± 1.3 ml·min(-1)·mmHg(-1)), while the old again exhibited no difference between postures (supine: 4.7 ± 0.4 ml·min(-1)·mmHg(-1); upright: 4.8 ± 0.5 ml·min(-1)·mmHg(-1)). Thus this study reveals that, unlike the young, increased FPP does not elicit an increase in movement-induced hyperemia or vasodilation in the old. In light of recent evidence that the majority of the first minute of passive movement-induced hyperemia is predominantly nitric oxide (NO) dependent in the young, these findings in the elderly may be largely due to decreased NO bioavailability, but this remains to be definitively determined.
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Affiliation(s)
- H Jonathan Groot
- Geriatric Research, Education, and Clinical Center Salt Lake City Veterans Affairs Medical Center, Salt Lake City, UT 84148, USA
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Gurovich AN, Braith RW. Enhanced external counterpulsation creates acute blood flow patterns responsible for improved flow-mediated dilation in humans. Hypertens Res 2012; 36:297-305. [DOI: 10.1038/hr.2012.169] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Heterogeneous vascular responses to hypoxic forearm exercise in young and older adults. Eur J Appl Physiol 2011; 112:3087-95. [PMID: 22198326 DOI: 10.1007/s00421-011-2280-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 12/05/2011] [Indexed: 10/14/2022]
Abstract
We aimed to assess age-related differences in compensatory hypoxic vasodilation during moderate-to-high dynamic exercise at absolute workloads. We hypothesized healthy older adults (n = 12, 61 ± 1 years) would exhibit impaired hypoxic vasodilation at a moderate absolute workload, and this effect would be exaggerated at a higher workload when compared to young adults (n = 17, 27 ± 2 years). Forearm blood flow (FBF) was measured with Doppler ultrasound. Dynamic forearm exercise (20 contractions/min) was completed at two absolute workloads (8 and 12 kg) under normoxic (0.21 FiO2, ~98% SpO2) and isocapnic hypoxic (~0.10 FiO2, 80% SpO2) conditions performed in random order. FBF was normalized as forearm vascular conductance (FBF / mean arterial blood pressure = FVC) to control for differences in blood pressure and to assess vasodilation. FVC increased with exercise and hypoxia (main effects, p < 0.05); vascular responses were not different between young and older adults (interaction effect exercise × group p = 0.37 and hypoxia × group p = 0.96). Results were confirmed when analyzed as either an absolute or relative change in FVC (ΔFVC and %ΔFVC, respectively). Although group responses to hypoxia were not different, individual results were highly variable (i.e., some adults constricted and others dilated to hypoxia). These data suggest (1) compensatory hypoxic vasodilation in older adults is not impaired during forearm exercise at both moderate and higher absolute exercise intensities, and (2) vascular responses to hypoxia are heterogeneous in both young and older adults. Results suggest unique individual differences exist in factors regulating vascular responses to hypoxia.
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Ives SJ, Andtbacka RHI, Noyes RD, McDaniel J, Amann M, Witman MAH, Symons JD, Wray DW, Richardson RS. Human skeletal muscle feed arteries studied in vitro: the effect of temperature on α(1)-adrenergic responsiveness. Exp Physiol 2011; 96:907-18. [PMID: 21685444 DOI: 10.1113/expphysiol.2011.059329] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Heat and cold exposure can decrease and increase total peripheral resistance, respectively, in humans. With unique access to human skeletal muscle feed arteries, we sought both to characterize these vessels and to determine the interaction between temperature and α(1)-adrenergic receptor responsiveness. We hypothesized that α(1)-mediated vasocontraction of human feed arteries would be attenuated in response to 39 or 35°C. Skeletal muscle feed arteries were harvested from thirty-two human volunteers and studied using isometric techniques. Vessel function was assessed using KCl, sodium nitroprusside (SNP), phenylephrine (PE) and ACh dose-response curves to characterize non-receptor- and receptor-mediated vasocontraction and vasorelaxation. Single doses of PE (1 mm) and KCl (100 mm) were administered at 37°C and then, in a balanced design, repeated at both 35 and 39°C. The KCl and PE dose-response curves elicited significant vasocontraction (2009 ± 407 and 1974 ± 508 mg developed tension, respectively), whereas SNP and ACh induced the expected vasorelaxation (102 ± 6 and 73 ± 10% relaxation, respectively). Altering the temperature had no effect on inherent smooth muscle function (KCl response), but both a reduction (35°C) and an increase in temperature (39°C) decreased the vasocontractile response to 1 mm PE (37°C, 1478 ± 338 mg; 35°C, 546 ± 104 mg; and 39°C, 896 ± 202 mg; P < 0.05) or across PE dose (P < 0.05, 35 and 39 versus 37°C). Despite clear heterogeneity between both the human volunteers and the feed arteries themselves, this novel approach to the procurement of human vessels revealed a robust 'inverted U' response to altered temperature, such that α(1)-mediated vasocontraction was attenuated with either warming or cooling.
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Affiliation(s)
- Stephen J Ives
- Geriatric Research Education and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT, USA
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