Capillary growth in relation to blood flow and performance in overloaded rat skeletal muscle

1998 ◽  
Vol 85 (6) ◽  
pp. 2025-2032 ◽  
Author(s):  
S. Egginton ◽  
O. Hudlická ◽  
M. D. Brown ◽  
H. Walter ◽  
J. B. Weiss ◽  
...  
Keyword(s):  
Blood Flow ◽  
Muscle Blood Flow ◽  
Tibialis Anterior Muscle ◽  
Mechanical Stimulus ◽  
Angiogenic Factor ◽  
Protein Distribution ◽  
Blood Flows ◽  
Capillary Growth ◽  
Capillary Bed ◽  
And Performance

Rat extensor digitorum longus muscles were overloaded by stretch after removal of the synergist tibialis anterior muscle to determine the relationship between capillary growth, muscle blood flow, and presence of growth factors. After 2 wk, sarcomere length increased from 2.4 to 2.9 μm. Capillary-to-fiber ratio, estimated from alkaline phosphatase-stained frozen sections, was increased by 33% ( P < 0.0001) and 60% ( P < 0.01), compared with control muscles (1.44 ± 0.06) after 2 and 8 wk, respectively. At 2 wk, the increased capillary-to-fiber ratio was not associated with any changes in mRNA for basic fibroblast growth factor (FGF-2) or its protein distribution. FGF-2 immunoreactivity was present in nerves and large blood vessels but was negative in capillaries, whereas the activity of low-molecular endothelial-cell-stimulating angiogenic factor (ESAF) was 50% higher in stretched muscles. Muscle blood flows measured by radiolabeled microspheres during contractions were not significantly different after 2 or 8 wk (132 ± 37 and 177 ± 22 ml ⋅ min−1 ⋅ 100 g−1, respectively) from weight-matched controls (156 ± 12 and 150 ± 10 ml ⋅ min−1 ⋅ 100 g−1, respectively). Resistance to fatigue during 5-min isometric contractions (final/peak tension × 100) was similar in 2-wk overloaded and contralateral muscles (85 vs. 80%) and enhanced after 8 wk to 92%, compared with 77% in contralateral muscles and 67% in controls. We conclude that increased blood flow cannot be responsible for initiating expansion of the capillary bed, nor does it explain the reduced fatigue within overloaded muscles. However, stretch can present a mechanical stimulus to capillary growth, acting either directly on the capillary abluminal surface or by upregulating ESAF, but not FGF-2, in the extracellular matrix.

Distribution of blood flow in muscles of miniature swine during exercise

1987 ◽  
Vol 62 (3) ◽  
pp. 1285-1298 ◽  
Author(s):  
R. B. Armstrong ◽  
M. D. Delp ◽  
E. F. Goljan ◽  
M. H. Laughlin
Keyword(s):  
Blood Flow ◽  
Exercise Intensity ◽  
Skeletal Muscles ◽  
Muscle Blood Flow ◽  
Peak Exercise ◽  
Fiber Types ◽  
Miniature Swine ◽  
Blood Flows ◽  
Limb Muscles ◽  
Total Muscle

The purpose of this study was to determine how the distribution of blood flow within and among the skeletal muscles of miniature swine (22 +/- 1 kg body wt) varies as a function of treadmill speed. Radiolabeled microspheres were used to measure cardiac output (Q) and tissue blood flows in preexercise and at 3–5 min of treadmill exercise at 4.8, 8.0, 11.3, 14.5, and 17.7 km/h. All pigs (n = 8) attained maximal O2 consumption (VO2max) (60 +/- 4 ml X min-1 X kg-1) by the time they ran at 17.7 km/h. At VO2max, 87% of Q (9.9 +/- 0.5 l/min) was to skeletal muscle, which constituted 36 +/- 1% of body mass. Average total muscle blood flow at VO2max was 127 +/- 14 ml X min-1 X 100 g-1; average limb muscle flow was 135 +/- 17 ml X min-1 X 100 g-1. Within the limb muscles, blood flow was distributed so that the deep red parts of extensor muscles had flows about two times higher than the more superficial white portions of the same muscles; the highest muscle blood flows occurred in the elbow flexors (brachialis: 290 +/- 44 ml X min-1 X 100 g-1). Peak exercise blood flows in the limb muscles were proportional (P less than 0.05) to the succinate dehydrogenase activities (r = 0.84), capillary densities (r = 0.78), and populations of oxidative (slow-twitch oxidative + fast-twitch oxidative-glycolytic) fiber types (r = 0.93) in the muscles. Total muscle blood flow plotted as a function of exercise intensity did not peak until the pigs attained VO2max, although flows in some individual muscles showed a plateau in this relationship at submaximal exercise intensities. The data demonstrate that blood flow in skeletal muscles of miniature swine is distributed heterogeneously and varies in relation to fiber type composition and exercise intensity.

Costal vs. crural diaphragmatic blood flow during submaximal and near-maximal exercise in ponies

1988 ◽  
Vol 65 (4) ◽  
pp. 1514-1519 ◽  
Author(s):  
M. Manohar
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Left Atrium ◽  
Maximal Exercise ◽  
Muscle Blood Flow ◽  
Intercostal Muscle ◽  
Quiet Breathing ◽  
Blood Flows ◽  
Graded Exercise ◽  
Crural Diaphragm

The present study was carried out 1) to compare blood flow in the costal and crural regions of the equine diaphragm during quiet breathing at rest and during graded exercise and 2) to determine the fraction of cardiac output needed to perfuse the diaphragm during near-maximal exercise. By the use of radionuclide-labeled 15-micron-diam microspheres injected into the left atrium, diaphragmatic and intercostal muscle blood flow was studied in 10 healthy ponies at rest and during three levels of exercise (moderate: 12 mph, heavy: 15 mph, and near-maximal: 19-20 mph) performed on a treadmill. At rest, in eucapnic ponies, costal (13 +/- 3 ml.min-1.100 g-1) and crural (13 +/- 2 ml.min-1.100 g-1) phrenic blood flows were similar, but the costal diaphragm received a much larger percentage of cardiac output (0.51 +/- 0.12% vs. 0.15 +/- 0.03% for crural diaphragm). Intercostal muscle perfusion at rest was significantly less than in either phrenic region. Graded exercise resulted in significant progressive increments in perfusion to these tissues. Although during exercise, crural diaphragmatic blood flow was not different from intercostal muscle blood flow, these values remained significantly less (P less than 0.01) than in the costal diaphragm. At moderate, heavy, and near-maximal exercise, costal diaphragmatic blood flow (123 +/- 12, 190 +/- 12, and 245 +/- 18 ml.min-1.100 g-1) was 143%, 162%, and 162%, respectively, of that for the crural diaphragm (86 +/- 10, 117 +/- 8, and 151 +/- 14 ml.min-1.100 g-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Regional circulatory responses to hypocapnia and hypercapnia in bar-headed geese

1986 ◽  
Vol 250 (3) ◽  
pp. R499-R504 ◽  
Author(s):  
F. M. Faraci ◽  
M. R. Fedde
Keyword(s):  
Blood Flow ◽  
Regional Blood Flow ◽  
Muscle Blood Flow ◽  
Pectoral Muscle ◽  
Blood Flows ◽  
Arterial Blood ◽  
Blood Flow Reduction ◽  
Extreme Altitude ◽  
Anser Indicus ◽  
O2 Delivery

To investigate mechanisms that may allow birds to tolerate extreme high altitude (hypocapnic hypoxia), we examined the effects of severe hypocapnia and moderate hypercapnia on regional blood flow in bar-headed geese (Anser indicus), a species that flies at altitudes up to 9,000 m. Cerebral, coronary, and pectoral muscle blood flows were measured using radioactive microspheres, while arterial CO2 tension (PaCO2) was varied from 7 to 62 Torr in awake normoxic birds. Arterial blood pressure was not affected by hypocapnia but increased slightly during hypercapnia. Heart rate did not change during alterations in PaCO2. Severe hypocapnia did not significantly alter cerebral, coronary, or pectoral muscle blood flow. Hypercapnia markedly increased cerebral and coronary blood flow, but pectoral muscle blood flow was unaffected. The lack of a blood flow reduction during severe hypocapnia may represent an important adaptation in these birds, enabling them to increase O2 delivery to the heart and brain at extreme altitude despite the presence of a very low PaCO2.

Muscle blood flow during exercise in sedentary and trained hypothyroid rats

1995 ◽  
Vol 269 (6) ◽  
pp. H1949-H1954 ◽  
Author(s):  
R. M. McAllister ◽  
M. D. Delp ◽  
K. A. Thayer ◽  
M. H. Laughlin
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Citrate Synthase ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Treadmill Running ◽  
Exercise Intolerance ◽  
Vastus Lateralis Muscle ◽  
Blood Flows ◽  
Vastus Intermedius

Hypothyroidism is characterized by exercise intolerance. We hypothesized that active muscle blood flow during in vivo exercise is inadequate in the hypothyroid state. Additionally, we hypothesized that endurance exercise training would restore normal blood flow during acute exercise. To test these hypotheses, rats were made hypothyroid (Hypo) over 3-4 mo with propylthiouracil. A subset of Hypo rats was trained (THypo) on a treadmill at 30 m/min (15% grade) for 60 min/day 5 days/wk over 10-15 wk. Hypothyroidism was evidenced by approximately 80% reductions in plasma triiodothyronine levels in Hypo and THypo and by 40-50% reductions in citrate synthase activities in high oxidative muscles in Hypo compared with euthyroid (Eut) rats. Training efficacy was indicated by increased (25-100%) citrate synthase activities in muscles of THypo vs. Hypo. Regional blood flows were determined by the radiolabeled microsphere method before exercise and at 1-2 min of treadmill running at 15 m/min (0% grade). Preexercise muscle blood flows were generally similar among groups. During exercise, however, flows were lower in Hypo than in Eut for high oxidative muscles such as the red section of vastus lateralis [277 +/- 24 and 153 +/- 13 (SE) ml.min-1.100 g-1 for Eut and Hypo, respectively; P < 0.01] and vastus intermedius (317 +/- 32 and 187 +/- 20 ml.min-1.100 g-1 for Eut and Hypo, respectively; P < 0.01) muscles. Training (THypo) did not normalize these flows (168 +/- 24 and 181 +/- 24 ml.min-1.100 g-1 for red section of vastus lateralis and vastus intermedius muscles, respectively). Blood flows to low oxidative muscle, such as the white section of vastus lateralis muscle, were similar among groups (21 +/- 5, 25 +/- 4, and 34 +/- 7 ml.min-1.100 g-1 for Eut, Hypo, and THypo, respectively; P = NS). These findings indicate that hypothyroidism is associated with reduced blood flow to skeletal muscle during exercise, suggesting that impaired delivery of nutrients to and/or removal of metabolites from skeletal muscle contributes to the poor exercise tolerance characteristic of hypothyroidism.

Angiogenesis in Skletal Muscle

Physiology ◽  
1986 ◽  
Vol 1 (5) ◽  
pp. 160-163
Author(s):  
HW Burton ◽  
JA Faulkner
Keyword(s):  
Skeletal Muscle ◽  
Endothelial Cells ◽  
Blood Flow ◽  
Vasoactive Agents ◽  
Adult Skeletal Muscle ◽  
Capillary Growth ◽  
Vascular Bed ◽  
Chronic Electrical Stimulation ◽  
Capillary Bed ◽  
Ischemic Muscle

Capillary growth is rarely observed in normal adult skeletal muscle, but angiogenesis may occur after injury to a capillary bed or after endurance training or chronic electrical stimulation. Revascularization of ischemic muscle may arise as inward growth from surrounding vascularized tissue, as outward growth from endothelial cells in ischemic muscle, or a combination of the two processes. A regenerated vascular bed shows diminished response to vasoactive agents and impaired regulation of blood flow during contractions.

Effects of intra-arterial arginine-vasopressin infusions on peripheral blood flows in conscious dogs

1986 ◽  
Vol 71 (6) ◽  
pp. 713-721 ◽  
Author(s):  
Jean-Francois Liard
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Small Intestine ◽  
Arginine Vasopressin ◽  
Muscle Blood Flow ◽  
Plasma Concentrations ◽  
Abdominal Fat ◽  
Conscious Dogs ◽  
Bone Blood Flow ◽  
Blood Flows

1. We reported in an earlier study that intravenous infusions of arginine-vasopressin (AVP), 220 pg min−1 kg−1 for 1 h, substantially reduced blood flow to the skin, skeletal muscle, pancreas, colon, small intestine, abdominal fat and myocardium [1] in conscious dogs. In the present study, we infused AVP directly into the artery supplying these organs and tissues in order to determine the relative contribution of local versus systemic mechanisms in the vascular resistance changes previously observed. 2. Regional blood flows were measured with radioactive microspheres in conscious, chronically instrumented dogs before and during intra-arterial infusions of AVP administered into the left axillary artery (n = 6), the left coronary artery (n = 6), and the cranial mesenteric artery (n = 6). The infusion rates were calculated to increase local, target organ plasma concentrations of AVP to the levels reached in our previous study while minimizing systemic changes. 3. Left axillary AVP artery infusion significantly reduced skin and compact bone blood flow, but had no effect on skeletal muscle blood flow. Intra-coronary AVP infusion had no effect on myocardial blood flow nor on cardiac output. Intramesenteric AVP infusion had no effect on blood flow to the colon, small intestine and abdominal fat, but significantly reduced blood flow to those areas of the pancreas which received blood from the cannulated artery. 4. Measurements in a limited number of dogs indicated that the local axillary and mesenteric venous levels of AVP were similar when the hormone was infused systemically at a rate of 220 pg min−1 kg−1 or intra-arterially at a lower rate. 5. These findings suggest that the increase in resistance measured in the skeletal muscle, small intestine, colon and abdominal fat after systemic administration of small amounts of AVP results in large part from indirect mechanisms. Direct vasoconstrictor effects of AVP at these plasma concentrations appear limited to the skin, the pancreas and the compact bones.

Respiratory muscle blood flows during physiological and chemical hyperpnea in the rat

2000 ◽  
Vol 88 (1) ◽  
pp. 186-194 ◽  
Author(s):  
David C. Poole ◽  
William L. Sexton ◽  
Bradley J. Behnke ◽  
Christine S. Ferguson ◽  
K. Sue Hageman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Respiratory Muscle ◽  
Maximal Exercise ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Oxidative Capacity ◽  
Blood Flows ◽  
Vasodilator Reserve ◽  
Exercise Muscle ◽  
Crural Diaphragm

Whether the diaphragm retains a vasodilator reserve at maximal exercise is controversial. To address this issue, we measured respiratory and hindlimb muscle blood flows and vascular conductances using radiolabeled microspheres in rats running at their maximal attainable treadmill speed (96 ± 5 m/min; range 71–116 m/min) and at rest while breathing either room air or 10% O2-8% CO2 (balance N2). All hindlimb and respiratory muscle blood flows measured increased during exercise ( P < 0.001), whereas increases in blood flow while breathing 10% O2-8% CO2 were restricted to the diaphragm only. During exercise, muscle blood flow increased up to 18-fold above rest values, with the greatest mass specific flows (in ml ⋅ min−1 ⋅ 100 g−1) found in the vastus intermedius (680 ± 44), red vastus lateralis (536 ± 18), red gastrocnemius (565 ± 47), and red tibialis anterior (602 ± 44). During exercise, blood flow was higher ( P < 0.05) in the costal diaphragm (395 ± 31 ml ⋅ min−1 ⋅ 100 g−1) than in the crural diaphragm (286 ± 17 ml ⋅ min−1 ⋅ 100 g−1). During hypoxia+hypercapnia, blood flows in both the costal and crural diaphragms (550 ± 70 and 423 ± 53 ml ⋅ min−1 ⋅ 100 g−1, respectively) were elevated ( P < 0.05) above those found during maximal exercise. These data demonstrate that there is a substantial functional vasodilator reserve in the rat diaphragm at maximal exercise and that hypoxia + hypercapnia-induced hyperpnea is necessary to elevate diaphragm blood flow to a level commensurate with its high oxidative capacity.

Effects of hyperthyroidism on muscle blood flow during exercise in rats

1995 ◽  
Vol 268 (1) ◽  
pp. H330-H335 ◽  
Author(s):  
R. M. McAllister ◽  
J. C. Sansone ◽  
M. H. Laughlin
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Citrate Synthase ◽  
Muscle Blood Flow ◽  
Left Ventricular ◽  
Submaximal Exercise ◽  
Treadmill Running ◽  
Exercise Intolerance ◽  
Blood Flows

Hyperthyroidism is associated with exercise intolerance. Previous research, however, has shown that cardiac output is either normal or enhanced during exercise in the hyperthyroid state. We therefore hypothesized that blood flow to working skeletal muscle is augmented in hyperthyroid animals during in vivo submaximal exercise and, consequently, that noncardiovascular factors are responsible for intolerance to exercise. To test this hypothesis, rats were made hyperthyroid (Hyper) over 6–12 wk with injections of triiodothyronine (300 micrograms/kg). Hyperthyroidism was evidenced by left ventricular hypertrophy [euthyroid (Eut), 2.12 +/- 0.05 mg/g body wt; Hyper, 2.78 +/- 0.06; P < 0.005], 25–60% increases in citrate synthase activities in Hyper hindlimb muscles over those of Eut rats, and higher preexercise heart rates (Eut, 415 +/- 18 beats/min; Hyper, 479 +/- 19; P < 0.025). Regional blood flows were determined by the radiolabeled microsphere method, preexercise, and at 1–2 min of treadmill running at 15 m/min (0% grade). Total hindlimb muscle blood flow preexercise was unaffected (Eut, 31 +/- 4 ml.min-1.(100) g-1, n = 11; Hyper, 40 +/- 6, n = 9; not significant) but was higher (P < 0.025) in Hyper (127 +/- 17, n = 9) compared with Eut (72 +/- 11, n = 9) during treadmill running. During exercise, flows to individual muscles and muscle sections were approximately 50–150% higher in Hyper compared with Eut rats. Visceral blood flows were largely similar between groups. These findings indicate that hyperthyroidism is associated with augmented blood flow to skeletal muscle during submaximal exercise. Thus hypoperfusion of skeletal muscle does not account for the poor exercise tolerance characteristic of hyperthyroidism.

Regional blood flows in salt loading hypertension in the dog

1981 ◽  
Vol 240 (3) ◽  
pp. H361-H367 ◽  
Author(s):  
J. F. Liard
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Cardiac Output ◽  
Arterial Pressure ◽  
Muscle Blood Flow ◽  
Peripheral Resistance ◽  
Salt Loading ◽  
Skeletal Muscle Blood Flow ◽  
Blood Flows ◽  
Regional Blood Flows

An intravenous infusion of isotonic sodium chloride, 196 ml/kg per day, was administered for several days to eight dogs with their renal mass reduced. Mean arterial pressure, cardiac output (electromagnetic flowmeter), and regional blood flows (radioactive microspheres) were measured sequentially and the results compared with those obtained in six control dogs. The salt-loaded animals exhibited on the 1st day of the infusion a 25% increase of arterial pressure and cardiac output. Blood flows to the kidney, the splanchnic area, the skin, and the bone were not significantly changed, whereas skeletal muscle blood flow almost doubled. After several days, cardiac output returned toward control values but pressure remained elevated. Skeletal muscle blood flow, as most other regional flows, did not differ significantly from control values at that time. In four dogs studied 6 h after starting a faster saline infusion, most of the increase in cardiac output was also distributed to the skeletal muscle. Total peripheral resistance changes did not reflect the resistance of individual beds, because vasoconstriction appeared early in some areas but was masked by prominent, although transient, vasodilation in skeletal muscle.

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