Effect of extracellular Po 2 on the fall in intracellular Po 2 in contracting single myocytes

2003 ◽  
Vol 94 (5) ◽  
pp. 1964-1970 ◽  
Author(s):  
Casey A. Kindig ◽  
Richard A. Howlett ◽  
Michael C. Hogan
Keyword(s):  
Skeletal Muscle ◽  
Time Delay ◽  
Time Constant ◽  
Initial Rate ◽  
Metabolic Response ◽  
Rate Of Change ◽  
Phosphorescence Quenching ◽  
Mean Response Time ◽  
The Mean ◽  
Lumbrical Muscles

The purpose of this investigation was to study the effects of altered extracellular Po 2 (Pe O2 ) on the intracellular Po 2(Pi O2 ) response to contractions in single skeletal muscle cells. Single myocytes ( n = 12) were dissected from lumbrical muscles of adult female Xenopus laevis and injected with 0.5 mM Pd- meso-tetra(4-carboxyphenyl)porphine for assessment of Pi O2 via phosphorescence quenching. At a Pe O2 of ∼20 (low), ∼40 (moderate), and ∼60 (high) Torr, tetanic contractions were induced at a frequency of 0.67 Hz for ∼2 min with a 5-min recovery between bouts (blocked order design). The Pi O2 response to contractions was characterized by a time delay followed by a monoexponential decline to steady-state (SS) values. The fall in Pi O2 to SS values was significantly greater at each progressively greater Pe O2 (all P < 0.05). The mean response time (time delay + time constant) was significantly faster in the low (35.2 ± 5.1 s; P < 0.05 vs. high) and moderate (43.3 ± 6.4 s; P < 0.05 vs. high) compared with high Pe O2 (61.8 ± 9.4 s) and was correlated positively ( r = 0.965) with the net fall in Pi O2 . However, the initial rate of change of Pi O2 (calculated as net fall in Pi O2 /time constant) was not different ( P > 0.05) among Pe O2 trials. These latter data suggest that, over the range of 20–60 Torr, Pe O2 does not play a deterministic role in setting the initial metabolic response to contractions in isolated frog myocytes. Additionally, these results suggest that oxidative phosphorylation in these myoglobin-free myocytes may be compromised by Pe O2 at values nearing 60 Torr.

Estimate of mean tissue O2 consumption at onset of exercise in males

1987 ◽  
Vol 63 (4) ◽  
pp. 1578-1585 ◽  
Author(s):  
M. D. Inman ◽  
R. L. Hughson ◽  
K. H. Weisiger ◽  
G. D. Swanson
Keyword(s):  
Mathematical Model ◽  
Cardiac Output ◽  
Time Delay ◽  
Impedance Cardiography ◽  
Work Rate ◽  
Rate Of Change ◽  
O2 Consumption ◽  
Weighted Mean ◽  
Mean Response Time ◽  
The Mean

A mathematical model has been developed that permitted the calculation of the flow-weighted mean tissue O2 consumption (VO2T) at the onset of a step increase in work rate. From breath-by-breath measurements of alveolar O2 consumption (VO2A) and cardiac output (Q) by impedance cardiography and assumptions about the site of depletion of O2 stores, the rate of change in O2 stores (VO2s) was determined. The sum of VO2A + VO2s = VO2T. Six very fit males performed six repetitions of each of two step increases in work rate. STlo was a transition from rest to 100-W cycling; SThi was a transition from 100- to 200-W cycling. For each work rate transition, the responses of VO2A and Q were averaged over the six repetitions of each subject and the model was solved to yield VO2T. The responses of VO2A, VO2T, and Q after the increase in work rate were fit with a monoexponential function. This function included a time constant and time delay, the sum of which gave the mean response time (MRT). In the STlo test, the MRT of VO2A (24.9 +/- 1.1 s, mean +/- SE) was longer than that of VO2T (15.3 +/- 1.3 s) and of Q (16.5 +/- 6.5 s) (P less than 0.05). The MRT of VO2T and Q did not differ significantly. Also for SThi, the MRT of VO2A (34.4 +/- 3.3 s) was significantly longer than that of VO2T (30.0 +/- 3.4 s) (P less than 0.05). The MRT of VO2T and Q (30.3 +/- 5.5 s) were not significantly different at this work rate either.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Intracellular Po2 kinetics at different contraction frequencies in Xenopus single skeletal muscle fibers

2007 ◽  
Vol 102 (4) ◽  
pp. 1456-1461 ◽  
Author(s):  
Richard A. Howlett ◽  
Casey A. Kindig ◽  
Michael C. Hogan
Keyword(s):  
Skeletal Muscle ◽  
Metabolic Response ◽  
Muscle Fibers ◽  
Metabolic Stress ◽  
Metabolic Demand ◽  
Phosphorescence Quenching ◽  
Contraction Frequency ◽  
Single Fibers ◽  
Mean Response Time ◽  
Skeletal Muscle Fibers

Increasing contraction frequency in single skeletal muscle fibers has been shown to increase the magnitude of the fall in intracellular Po2 (PiO2), reflecting a greater metabolic rate. To test whether PiO2 kinetics are altered by contraction frequency through this increase in metabolic stress, PiO2 was measured in Xenopus single fibers ( n = 11) during and after contraction bouts at three different frequencies. PiO2 was measured via phosphorescence quenching at 0.16-, 0.25-, and 0.5-Hz tetanic stimulation. The kinetics of the change in PiO2 from resting baseline to end-contraction values and end contraction to rest were described as a mean response time (MRT) representing the time to 63% of the change in PiO2. As predicted, the fall in PiO2 from baseline following contractions was progressively greater at 0.5 and 0.25 Hz than at 0.16 Hz (32.8 ± 2.1 and 29.3 ± 2.0 Torr vs. 23.6 ± 2.2 Torr, respectively) since metabolic demand was greater. The MRT for the decrease in PiO2 was progressively faster at the higher frequencies (0.5 Hz: 45.3 ± 4.5 s; 0.25 Hz: 63.3 ± 4.1 s; 0.16 Hz: 78.0 ± 4.1 s), suggesting faster accumulation of stimulators of oxidative phosphorylation. The MRT for PiO2 off-kinetics (0.5 Hz: 84.0 ± 11.7 s; 0.25 Hz: 79.1 ± 8.4 s; 0.16 Hz: 81.1 ± 8.3 s) was not different between trials. These data demonstrate in single fibers that the rate of the fall in PiO2 is dependent on contraction frequency, whereas the rate of recovery following contractions is independent of either the magnitude of the fall in PiO2 from baseline or the contraction frequency. This suggests that stimulation frequency plays an integral role in setting the initial metabolic response to work in isolated muscle fibers, possibly due to temporal recovery between contractions, but it does not determine recovery kinetics.

Effect of contractile duration on intracellular Po2 kinetics in Xenopus single skeletal myocytes

2005 ◽  
Vol 98 (5) ◽  
pp. 1639-1645 ◽  
Author(s):  
Casey A. Kindig ◽  
Richard A. Howlett ◽  
Michael C. Hogan
Keyword(s):  
Fiber Type ◽  
Rate Of Change ◽  
Whole Body ◽  
Transient Kinetics ◽  
Phosphorescence Quenching ◽  
First Order ◽  
Skeletal Myocytes ◽  
Mean Response Time ◽  
Contraction Duration ◽  
Initial Onset

It has been suggested that skeletal muscle O2 uptake (V̇o2) kinetics follow a first-order control model. Consistent with that, V̇o2 should show both 1) similar onset kinetics and 2) an on-off symmetry across submaximal work intensities regardless of the metabolic perturbation. To date, consensus on this issue has not been reached in whole body studies due to numerous confounding factors associated with O2 availability and fiber-type recruitment. To test whether single myocytes demonstrate similar intracellular Po2 (PiO2) on- and off-transient kinetics at varying work intensities, we studied Xenopus laevis single myocyte ( n = 8) PiO2 via phosphorescence quenching during two bouts of electrically induced isometric muscle contractions of 200 (low)- and 400 (high)-ms contraction duration (1 contraction every 4 s, 15 min between trials, order randomized). The fall in PiO2, which is inversely proportional to the net increase in V̇o2, was significantly greater ( P < 0.05) during the high (24.1 ± 3.2 Torr) vs. low (17.4 ± 1.6 Torr) contraction bout. However, the mean response time (MRT; time to 63% of the overall change) for the fall in PiO2 from resting baseline to end contractions was not different (high, 77.8 ± 11.5 vs. low, 76.1 ± 13.6 s; P > 0.05) between trials. The initial rate of change at contraction onset, defined as ΔPiO2/MRT, was significantly greater ( P < 0.05) in high compared with low. PiO2 off-transient MRT from the end of the contraction bout to initial baseline was unchanged (high, 83.3 ± 18.3 vs. low, 80.4 ± 21.6 s; P > 0.05) between high and low trials. These data revealed that PiO2 dynamics in frog isolated skeletal myocytes were invariant despite differing contraction durations and, by inference, metabolic demands. Thus these findings demonstrate that mitochondria can respond more rapidly at the initial onset of contractions when challenged with an augmented metabolic stimulus in accordance with an apparent first-order rate law.

Thermal diffusion in solutions of electrolytes

1960 ◽  
Vol 255 (1282) ◽  
pp. 307-330 ◽  
Keyword(s):  
Steady State ◽  
Initial Rate ◽  
Wheatstone Bridge ◽  
Rate Of Change ◽  
Soret Coefficient ◽  
Free System ◽  
Platinized Platinum ◽  
Solutions Of Electrolytes ◽  
Concentration Changes ◽  
The Mean

A conductimetric method for following the small concentration changes that occur when a temperature gradient is maintained in an aqueous electrolyte is described. The solution is contained in a Perspex cell between silver end-plates which are faced with platinized platinum and kept at temperatures differing by about 10°C. A further connexion to the cell (a ‘centretap’) is made through a small lateral hole equidistant from the ends. The cell is incorporated in an audio-frequency Wheatstone bridge and movement of solute from one half of the cell to the other is followed by measuring the ratio of their resistances. For a convection-free system, the Soret coefficient (σ) may be derived either from the initial rate of change of the ratio or from its value in the steady state. It is found experimentally that there are discrepancies between the two estimates of σ, and also related anomalies in the rate of change of concentration, which can be ascribed to convection. It can be shown that the initial rate observations should be free from convection errors, and the effect of convection on the steady state can be analysed by dimensional methods. The observed discrepancies are correlated with the relevant properties of the solutions in the manner suggested by this analysis. The Soret coefficients of eighteen 1:1 salts in 0⋅01 m aqueous solution and at mean temperature 25⋅0°C have been determined by this method. Some additional measurements have been made at 34⋅7°C and at other concentrations in the range 0⋅002 to 0⋅02m. Three salts of other valency types (potassium, thallous and cadmium sulphates) have also been studied. The molar heats of transport of the salts ( Q *) have been calculated from the Soret coefficients. The results show that Q * (i) is an additive function of contributions characteristic of the constituent ions in dilute (0⋅01 M) solutions of 1:1 electrolytes, (ii) increases markedly on raising the mean temperatures from 25⋅0 to 34⋅7°C, in agreement with the results of Alexander (1954) and Longsworth (1957) (iii) increases appreciably on dilution below 0⋅01 M, indicating that heats of transport are influenced by long-range inter-ionic forces.

Relationship between intracellular Po2 recovery kinetics and fatigability in isolated single frog myocytes

2005 ◽  
Vol 98 (6) ◽  
pp. 2316-2319 ◽  
Author(s):  
Casey A. Kindig ◽  
Brandon Walsh ◽  
Richard A. Howlett ◽  
Creed M. Stary ◽  
Michael C. Hogan
Keyword(s):  
Negative Relationship ◽  
Oxidative Capacity ◽  
Metabolic Demand ◽  
Constant Frequency ◽  
Phosphorescence Quenching ◽  
Skeletal Myocytes ◽  
Mean Response Time ◽  
Lumbrical Muscle ◽  
The Mean ◽  
The Relationship

In single frog skeletal myocytes, a linear relationship exists between “fatigability” and oxidative capacity. The purpose of this investigation was to study the relationship between the intracellular Po2 (PiO2) offset kinetics and fatigability in single Xenopus laevis myocytes to test the hypothesis that PiO2 offset kinetics would be related linearly with myocyte fatigability and, by inference, oxidative capacity. Individual myocytes ( n = 30) isolated from lumbrical muscle were subjected to a 2-min bout of isometric peak tetanic contractions at either 0.25- or 0.33-Hz frequency while PiO2 was measured continuously via phosphorescence quenching techniques. The mean response time (MRT; time to 63% of the overall response) for PiO2 recovery from contracting values to resting baseline was calculated. After the initial square-wave constant-frequency contraction trial, each cell performed an incremental contraction protocol [i.e., frequency increase every 2 min from 0.167, 0.25, 0.33, 0.5, 1.0, and 2.0 Hz until peak tension fell below 50% of initial values (TTF)]. TTF values ranged from 3.39 to 10.04 min for the myocytes. The PiO2 recovery MRT ranged from 26 to 146 s. A significant ( P < 0.05), negative relationship (MRT = −12.68TTF + 168.3, r2 = 0.605) between TTF and PiO2 recovery MRT existed. These data demonstrate a significant correlation between fatigability and oxidative phosphorylation recovery kinetics consistent with the notion that oxidative capacity determines, in part, the speed with which skeletal muscle can recover energetically to alterations in metabolic demand.

scholarly journals Skeletal muscle interstitial Po2 kinetics during recovery from contractions

2019 ◽  
Vol 127 (4) ◽  
pp. 930-939 ◽  
Author(s):  
Daniel M. Hirai ◽  
Jesse C. Craig ◽  
Trenton D. Colburn ◽  
Hiroaki Eshima ◽  
Yutaka Kano ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Time Course ◽  
Fick’S Law ◽  
Diffusing Capacity ◽  
Phosphorescence Quenching ◽  
Fick's Law ◽  
Mean Response Time ◽  
Repetitive Tasks ◽  
The Face ◽  
Considerable Resistance

The oxygen partial pressure in the interstitial space (Po2 is) drives O2 into the myocyte via diffusion, thus supporting oxidative phosphorylation. Although crucial for metabolic recovery and the capacity to perform repetitive tasks, the time course of skeletal muscle Po2 is during recovery from contractions remains unknown. We tested the hypothesis that Po2 is would recover to resting values and display considerable on-off asymmetry (fast on-, slow off-kinetics), reflective of asymmetric capillary hemodynamics. Microvascular Po2 (Po2 mv) was also evaluated to test the hypothesis that a significant transcapillary gradient (ΔPo2 = Po2 mv − Po2 is) would be sustained during recovery. Po2 mv and Po2 is (expressed in mmHg) were determined via phosphorescence quenching in the exposed rat spinotrapezius muscle during and after submaximal twitch contractions ( n = 12). Po2 is rose exponentially ( P < 0.05) from end-contraction (11.1 ± 5.1), such that the end-recovery value (17.9 ± 7.9) was not different from resting Po2 is (18.5 ± 8.1; P > 0.05). Po2 is off-kinetics were slower than on-kinetics (mean response time: 53.1 ± 38.3 versus 18.5 ± 7.3 s; P < 0.05). A significant transcapillary ΔPo2 observed at end-contraction (16.6 ± 7.4) was maintained throughout recovery (end-recovery: 18.8 ± 9.6; P > 0.05). Consistent with our hypotheses, muscle Po2 is recovered to resting values with slower off-kinetics compared with the on-transient in line with the on-off asymmetry for capillary hemodynamics. Maintenance of a substantial transcapillary ΔPo2 during recovery supports that the microvascular-interstitium interface provides considerable resistance to O2 transport. As dictated by Fick’s law (V̇o2 = Do2 × ΔPo2), modulation of O2 flux (V̇o2) during recovery must be achieved via corresponding changes in effective diffusing capacity (Do2; mainly capillary red blood cell hemodynamics and distribution) in the face of unaltered ΔPo2. NEW & NOTEWORTHY Capillary blood-myocyte O2 flux (V̇o2) is determined by effective diffusing capacity (Do2; mainly erythrocyte hemodynamics and distribution) and microvascular-interstitial Po2 gradients (ΔPo2 = Po2 mv − Po2 is). We show that Po2 is demonstrates on-off asymmetry consistent with Po2 mv and erythrocyte kinetics during metabolic transitions. A substantial transcapillary ΔPo2 was preserved during recovery from contractions, indicative of considerable resistance to O2 diffusion at the microvascular-interstitium interface. This reveals that effective Do2 declines in step with V̇o2 during recovery, as per Fick’s law.

A frequency and time domain study of the horizontal and vertical vestibuloocular reflex in the pigeon

1988 ◽  
Vol 59 (4) ◽  
pp. 1143-1161 ◽  
Author(s):  
T. J. Anastasio ◽  
M. J. Correia
Keyword(s):  
Time Delay ◽  
Frequency Response ◽  
Time Constant ◽  
Mean Value ◽  
Step Response ◽  
Phase Lag ◽  
Vestibuloocular Reflex ◽  
Stimulus Magnitude ◽  
Response Data ◽  
The Mean

1. The horizontal and vertical vestibuloocular reflex (HVOR and VVOR, respectively) was studied in four chronically instrumented pigeons. Eye movements were measured using the magnetic search-coil technique and were produced by rotation in the dark. During the rotation paradigms, the pigeons were either pharmacologically aroused (using amphetamine) or drug free (normal). The pigeon HVOR and VVOR were tested using step and sinusoidal rotational stimulation. The range of frequencies (0.03-6.0 Hz) and the magnitude of the sinusoidal stimuli were chosen to match those used in a previous study of the responses of semicircular canal primary afferents (SCPAs) in unanesthetized (i.e., normal) pigeons. 2. The gain of the HVOR and VVOR in both normal and aroused pigeons was independent of stimulus magnitude (6-30 degrees/s) over the frequency range tested. In aroused pigeons, the frequency independent gain (G) of the HVOR (G = 0.6) and VVOR (G = 0.9) was roughly twice that for normal pigeons. Pigeon VOR phase under all combinations of orientation and arousal level was independent of stimulus magnitude except at the lowest frequency tested (0.03 Hz). At this frequency, phase lead decreased as stimulus magnitude increased for the HVOR and VVOR in both normal and aroused pigeons. 3. The step and sinusoidal gains were greater for the VVOR than for the HVOR under the same level of arousal. Neither the gain nor the dominant time constant of the VOR (tau vor) differed for rotation direction (clockwise or counterclockwise) for the HVOR or VVOR in normal or aroused pigeons. 4. The mean value of tau vor was 4.0 +/- 0.5 (SE) s as estimated from frequency response data and 4.3 +/- 0.4 s as estimated from step response data for the HVOR and VVOR in both normal and aroused pigeons. In comparison, the mean value of the dominant or cupular time constant (tau c) of normal pigeon SCPAs was approximately 10 s as estimated from frequency response data. These results indicate that tau vor is shorter than tau c in the pigeon. 5. At higher frequencies, the pigeon HVOR and VVOR exhibit an increasing phase lag unaccompanied by a gain change--characteristics produced by a pure time delay. The value of this time delay was about 7 ms for both the HVOR and VVOR in both normal and aroused pigeons. The HVOR and VVOR in normal and aroused pigeons lacked the higher frequency lead characteristics present in the frequency responses of most pigeon SCPAs.

Dynamics of microvascular oxygen pressure during rest-contraction transition in skeletal muscle of diabetic rats

2002 ◽  
Vol 283 (3) ◽  
pp. H926-H932 ◽  
Author(s):  
Bradley J. Behnke ◽  
Casey A. Kindig ◽  
Paul McDonough ◽  
David C. Poole ◽  
William L. Sexton
Keyword(s):  
Skeletal Muscle ◽  
Type I Diabetes ◽  
Dynamic Balance ◽  
Diabetic Rats ◽  
Type I ◽  
Least Squares Regression ◽  
Exponential Process ◽  
Phosphorescence Quenching ◽  
Mean Response Time ◽  
To Receive

Type I diabetes reduces dramatically the capacity of skeletal muscle to receive oxygen (Q˙o 2). In control (C; n = 6) and streptozotocin-induced diabetic (D: n = 6, plasma glucose = 25.3 ± 3.9 mmol/l and C: 8.3 ± 0.5 mmol/l) rats, phosphorescence quenching was used to test the hypothesis that, in D rats, the decline in microvascular Po 2 [PmO2 , which reflects the dynamic balance between O2 utilization (V˙o 2) andQ˙o 2] of the spinotrapezius muscle after the onset of electrical stimulation (1 Hz) would be faster compared with that of C rats. PmO2 data were fit with a one or two exponential process (contingent on the presence of an undershoot) with independent time delays using least-squares regression analysis. In D rats, PmO2 at rest was lower (C: 31.2 ± 3.2 mmHg; D: 24.3 ± 1.3 mmHg, P < 0.05) and at the onset of contractions decreased after a shorter delay (C: 13.5 ± 1.8 s; D: 7.6 ± 2.1 s, P < 0.05) and with a reduced mean response time (C: 31.4 ± 3.3 s; D: 23.9 ± 3.1 s, P < 0.05). PmO2 exhibited a marked undershoot of the end-stimulation response in D muscles (D: 3.3 ± 1.1 mmHg, P < 0.05), which was absent in C muscles. These results indicate an alteredV˙o 2-to-Q˙o 2matching across the rest-exercise transition in muscles of D rats.

Adaptation speed of cardiac mitochondrial oxygen consumption decreases with higher heart rate

1993 ◽  
Vol 265 (6) ◽  
pp. H1893-H1898 ◽  
Author(s):  
M. H. Eijgelshoven ◽  
J. B. Hak ◽  
J. H. Van Beek ◽  
N. Westerhof
Keyword(s):  
Skeletal Muscle ◽  
Heart Rate ◽  
Oxygen Consumption ◽  
Response Time ◽  
Metabolic Demand ◽  
Average Delay ◽  
Mitochondrial Oxygen Consumption ◽  
Atp Production ◽  
Mean Response Time ◽  
The Mean

The purpose of the present study was to determine whether the mean response time of cardiac mitochondrial oxygen consumption after a step in metabolic demand is constant in heart muscle, as has already been found for skeletal muscle. The mean response time reflects the average delay between the change in ATP hydrolysis due to a heart rate step and mitochondrial ATP production. Isolated rabbit hearts with a water-filled balloon in the left ventricle were perfused according to Langendorff with a constant flow of Tyrode solution at 28 degrees C. The mean response time increased significantly from 7.6 s for a step in heart rate from 60 to 70 min-1 to 12.1 s for a step from 60 to 120 min-1. The mean response times for heart rate steps downward from 120 min-1 were all approximately 12 s, but for the step from 120 to 140 min-1 the response time was 16.8 s. These results demonstrate that the mean response time of cardiac mitochondrial oxygen consumption in most cases increases with heart rate. These findings are in contrast to those obtained in skeletal muscle, where the response time at which ATP synthesis adapts to a change in work load is constant.

scholarly journals Aging blunts the dynamics of vasodilation in isolated skeletal muscle resistance vessels

2010 ◽  
Vol 108 (1) ◽  
pp. 14-20 ◽  
Author(s):  
Bradley J. Behnke ◽  
Michael D. Delp
Keyword(s):  
Skeletal Muscle ◽  
Old Age ◽  
Time Constant ◽  
Rate Of Change ◽  
Fischer 344 ◽  
Resistance Vessels ◽  
Monoexponential Model ◽  
Mechanistic Basis ◽  
O 24

Aging is associated with an altered ability to match oxygen delivery (Qo2) to consumption (V̇o2) in skeletal muscle and differences in the temporal profile of vasodilation may provide a mechanistic basis for the Qo2-to-V̇o2 mismatching during the rest-to-exercise transition. Therefore, we tested the hypothesis that the speed of vasodilation will be blunted in skeletal muscle first-order arterioles from old vs. young rats. Arterioles from the soleus and the red portion of the gastrocnemius (GastRed) muscles were isolated from young (Y, 6 mo; n = 9) and old (O, 24 mo; n = 9) Fischer 344 rats and studied in vitro. Vessels were exposed to acetylcholine (ACh; 10−6 M), sodium nitroprusside (SNP; 10−4 M), and increased intraluminal flow, and the subsequent vasodilation was recorded at 30 frames/s. The data were fit to a monoexponential model and the dynamics of vasodilation [i.e., time delay, time constant (tau), and rate of change (delta/tau)] were calculated. With old age, the rate of vasodilation was significantly blunted in resistance vessels from the soleus to ACh (Y, 27.9 ± 3.6; O, 8.8 ± 2.6 μm/s) and flow (Y, 12.8 ± 2.1; O, 3.1 ± 0.9 μm/s). In the GastRed the old age-associated impairment of endothelium-dependent vasodilator dynamics was even greater than that of the soleus. With SNP neither the magnitude nor time constant of vasodilation was affected by age in either muscle. The results indicate that aging impairs the dynamics of vasodilation in resistance vessels from the soleus and GastRed muscles mediated, in part, through the endothelium. Thus the old age-associated slower rate and magnitude of vasodilation could inhibit the delivery of O2 during the critical transition from rest to exercise in moderate to highly oxidative skeletal muscle.

Sign in / Sign up

Export Citation Format

Share Document