Endothelial independence of myogenic response in isolated skeletal muscle arterioles

1991 ◽  
Vol 260 (1) ◽  
pp. H130-H135 ◽  
Author(s):  
J. C. Falcone ◽  
M. J. Davis ◽  
G. A. Meininger
Keyword(s):  
Skeletal Muscle ◽  
In Vitro Study ◽  
Intraluminal Pressure ◽  
Myogenic Response ◽  
First Order ◽  
Basal Tone ◽  
Spontaneous Tone ◽  
Flow Through ◽  
Myogenic Activity

The goal of this study was to determine whether the endothelium played a role in the myogenic response of skeletal muscle arterioles. First-order arterioles (n = 15) were isolated from the rat cremaster muscle and cannulated for in vitro study. The development of spontaneous tone reduced the diameter of the isolated arterioles from 166.7 +/- 7.6 microns to 89.2 +/- 7.2 microns. The arterioles were exposed to step changes in intraluminal pressure over a range of 10–170 cmH2O and had no flow through their lumen. The vessels exhibited active constriction to step increases or active dilation to step decreases in pressure (50–150 cmH2O). At 90 cmH2O, arterioles dilated by 89.2 +/- 6.0% in response to the endothelium-dependent vasodilator acetylcholine (10(-6) M; ACh) and 89.6 +/- 10.9% in response to endothelium-independent dilator adenosine (10(-4) M; Ado). The endothelium was physically denuded by rubbing the vessel lumen. After denudation, the arteriolar dilation to ACh was abolished, whereas the dilation to Ado was unaltered. The absence of endothelium was verified by electron microscopy. Basal tone and the response to changes in pressure were not significantly different from endothelium-intact vessels. These studies indicate that the endothelium is not responsible for myogenic activity or development of spontaneous tone in skeletal muscle arterioles.

Myogenic and vasoconstrictor responsiveness of skeletal muscle arterioles is diminished by hindlimb unloading

1999 ◽  
Vol 86 (4) ◽  
pp. 1178-1184 ◽  
Author(s):  
Michael D. Delp
Keyword(s):  
Skeletal Muscle ◽  
In Vitro Study ◽  
Hindlimb Unloading ◽  
Intraluminal Pressure ◽  
Type I ◽  
Maximal Diameter ◽  
Vasoconstrictor Response ◽  
Spontaneous Tone ◽  
C 30

The purpose of the present study was to determine whether hindlimb unloading of rats alters vasoconstrictor and myogenic responsiveness of skeletal muscle arterioles. After either 2 wk of hindlimb unloading (HU) or cage control (C), second-order arterioles were isolated from the white portion of gastrocnemius (WG; C: n = 9, HU: n = 10) or soleus (Sol; C: n = 9, HU: n = 10) muscles and cannulated with two micropipettes connected to reservoir systems for in vitro study. Intraluminal pressure was set at 60 cmH2O. The arterioles were exposed to step changes in intraluminal pressure ranging from 20 to 140 cmH2O to determine myogenic responsiveness and to KCl (10–100 mM) and norepinephrine (10−9–10−4M) to determine vasoconstrictor responsiveness. Although maximal diameter of WG arterioles was not different between C (185 ± 12 μm) and HU (191 ± 14 μm) rats, WG arterioles from HU rats developed less spontaneous tone (C: 33 ± 5%, HU 20 ±3%), were unable to maintain myogenic tone at pressures from 140 to 100 cmH2O, and were less sensitive to the vasoconstrictor effects of KCl and norepinephrine (as indicated by a higher agonist concentration that produced 50% of maximal vasoconstrictor response). In contrast, maximal diameter of Sol arterioles from HU rats (117 ± 12 μm) was smaller than that in C rats (148 ± 14 μm). However, the development of spontaneous tone (C: 30 ± 4%, HU: 36 ± 5%), myogenic activity, and the responsiveness to vasoconstrictor agonists were not different between Sol arterioles from C and HU rats. These results indicate that hindlimb unloading diminishes the myogenic autoregulatory and contractile responsiveness of arterioles from muscle composed of type IIB fibers and suggest that the compromised ability to elevate vascular resistance after exposure to microgravity may be related to these vascular alterations. In addition, hindlimb unloading appears to induce vascular remodeling of arterioles from muscle composed of type I fibers, as indicated by the decrease in maximal diameter of arterioles from Sol muscle.

Myogenic responses of isolated rat skeletal muscle venules: modulation by norepinephrine and endothelium

1996 ◽  
Vol 271 (1) ◽  
pp. H267-H272 ◽  
Author(s):  
G. Dornyei ◽  
E. Monos ◽  
G. Kaley ◽  
A. Koller
Keyword(s):  
Skeletal Muscle ◽  
Adrenergic Receptor ◽  
Perfusion Pressure ◽  
Receptor Activation ◽  
Intraluminal Pressure ◽  
Negative Slope ◽  
Internal Diameter ◽  
Myogenic Response ◽  
First Order ◽  
Diameter Curve

The pressure-induced myogenic response of large venules of skeletal muscle and its possible interactions with adrenergic receptor activation and endothelial factors have not yet been elucidated. Therefore, first-order venules of rat gracilis muscle were isolated, cannulated, and placed in an organ chamber. Changes in internal diameter of the vessels as a function of perfusion pressure (PP) were obtained. In response to increases in PP (0.5-17.5 mmHg), the diameter of venules increased from 197.1 +/- 23.96 to 369 +/- 14.1 microns. In passive conditions (in Ca(2+)-free solution), the pressure-diameter curve of venules shifted significantly upward. In the presence of norepinephrine (NE; 10(-6) M) in the bath solution, the pressure-diameter curve of active venules shifted significantly downward, and in the pressure-normalized diameter curve, a negative slope developed (-6.1 +/- 4.6). In both the absence and presence of NE, removal of endothelium significantly reduced venular diameters in the pressure ranges of 3-5 and 2-5 mmHg, respectively, but did not change significantly the characteristics of the pressure-diameter curves. These findings indicate that the smooth muscle of venules actively responds to changes in intraluminal pressure. This response is greatly facilitated by NE and modulated by the endothelium. The myogenic response of skeletal muscle venules, especially in the presence of NE, could have a role in the regulation of the resistance and capacitance of venules and, consequently, blood flow and tissue exchange in skeletal muscle.

Myogenic activity in isolated subepicardial and subendocardial coronary arterioles

1988 ◽  
Vol 255 (6) ◽  
pp. H1558-H1562 ◽  
Author(s):  
L. Kuo ◽  
M. J. Davis ◽  
W. M. Chilian
Keyword(s):  
High Pressures ◽  
In Vitro Study ◽  
Intraluminal Pressure ◽  
Physiological Salt Solution ◽  
India Ink ◽  
Myogenic Activity ◽  
Myogenic Responses ◽  
Pressure Changes ◽  
Coronary Arterioles

The goal of this study was to examine myogenic responses of isolated porcine subepicardial and subendocardial arterioles (80–100 micron in diameter) within physiological ranges of intraluminal pressure. Arterioles were located by perfusion with india ink-gelatin solution then dissected and cannulated with glass micropipettes. Intraluminal pressure was altered in 20-cmH2O steps over the range of 20–140 cmH2O. IN physiological salt solution (36–37 degrees C), the coronary arterioles developed spontaneous tone and exhibited myogenic responses. At the lower pressures (20–60 cmH2O), subendocardial arterioles responded passively (diameter decreased from a control diameter at 60 cmH2O), whereas subepicardial arterioles maintained their diameters. At higher pressures (100–140 cmH2O), both subepicardial and subendocardial arterioles demonstrated myogenic constriction, but subepicardial arterioles demonstrated greater myogenic constriction than subendocardial arterioles. This implies that myogenic autoregulation in subepicardial arterioles is better than that in the subendocardial arterioles at both low and high pressures. In the presence of nitroprusside (10(-4) M), all arterioles responded to pressure changes passively, and there were no differences between subepicardial and subendocardial vessels. The functional integrity of the endothelium was verified by relaxation to substance P (10(-7) M). This is the first in vitro study to demonstrate coronary myogenic activity and transmural differences in these arteriolar responses. Our data support the concept that myogenic mechanisms in 80 to 100-micron arterioles may actively contribute to autoregulation of coronary blood flow.

αvβ3- and α5β1-integrin blockade inhibits myogenic constriction of skeletal muscle resistance arterioles

2005 ◽  
Vol 289 (1) ◽  
pp. H322-H329 ◽  
Author(s):  
Luis A. Martinez-Lemus ◽  
Tracy Crow ◽  
Michael J. Davis ◽  
Gerald A. Meininger
Keyword(s):  
Skeletal Muscle ◽  
Vessel Diameter ◽  
Significant Inhibition ◽  
Intraluminal Pressure ◽  
Rat Skeletal Muscle ◽  
Histocompatibility Complex ◽  
Spontaneous Tone ◽  
And Function ◽  
Blocking Antibodies ◽  
Α5β1 Integrin

In isolated resistance arterioles with spontaneous tone, ligation of α4β1- and α5β1-integrins induces vasoconstriction whereas ligation of αvβ3-integrin induces vasodilation. However, whether integrins directly participate in myogenic constriction to pressure elevation is not known. To answer this question, isolated rat skeletal muscle arterioles were exposed to step increments in pressure in the absence or presence of peptides and function-blocking antibodies known to bind α4β1-, α5β1-, or αvβ3-integrins while vessel diameter was continually monitored. Myogenic constriction, as assessed by the ability of isolated arterioles to reduce their diameter in response to two consecutive increments in intraluminal pressure (90–110 and 110–130 cmH2O), was not affected by treatment with any of the control peptides (RAD, LEV), a control antibody (anti-rat major histocompatibility complex), an α4β1-integrin-binding peptide (LDV), or an anti-α4-integrin antibody. In contrast, α5β1-integrin blockade with either anti-α5- or anti-β1-integrin antibody caused a significant inhibition of myogenic constriction. Also, both RGD peptide and anti-β3-integrin antibody inhibited myogenic constriction. These results indicate that α5β1- and αvβ3-integrins are necessary for myogenic constriction and further suggest that integrins are part of the mechanosensory apparatus responsible for the ability of vascular smooth muscle cells to detect and/or respond to changes in intraluminal pressure.

scholarly journals In Vitro Study of Mechanical and Kinetic Properties of Myosin II from Frog Skeletal Muscle

2009 ◽  
Vol 96 (3) ◽  
pp. 614a
Author(s):  
Ravikrishnan Elangovan ◽  
Marco Capitanio ◽  
Francesco S. Pavone ◽  
Vincenzo Lombardi
Keyword(s):  
Skeletal Muscle ◽  
Myosin Ii ◽  
In Vitro Study ◽  
Vitro Study ◽  
Kinetic Properties ◽  
Frog Skeletal Muscle

Nonuniform changes in arteriolar myogenic tone within skeletal muscle following hindlimb unweighting

2002 ◽  
Vol 92 (3) ◽  
pp. 1145-1151 ◽  
Author(s):  
Cristine L. Heaps ◽  
Douglas K. Bowles
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Weight Bearing ◽  
Intraluminal Pressure ◽  
Myogenic Tone ◽  
Hindlimb Unweighting ◽  
Channel Current ◽  
Spontaneous Tone ◽  
Fast Twitch ◽  
And Control

Hindlimb unweighting (HLU) has been shown to alter myogenic tone distinctly in arterioles isolated from skeletal muscles composed predominantly of fast-twitch (white gastrocnemius) compared with slow-twitch (soleus) fibers. Based on these findings, we hypothesized that HLU would alter myogenic tone differently in arterioles isolated from distinct fiber-type regions within a single skeletal muscle. We further hypothesized that alterations in myogenic tone would be associated with alterations in voltage-gated Ca2+ channel current (VGCC) density of arteriolar smooth muscle. After 14 days of HLU or weight bearing (control), first-order arterioles were isolated from both fast-twitch and mixed fiber-type regions of the gastrocnemius muscle, cannulated, and pressurized at 90 cmH2O. Mixed gastrocnemius arterioles of HLU rats demonstrated increased spontaneous tone [43 ± 5% (HLU) vs. 27 ± 4% (control) of possible constriction] and an approximately twofold enhanced myogenic response when exposed to step changes in intraluminal pressure (10–130 cmH2O) compared with control rats. In contrast, fast-twitch gastrocnemius arterioles of HLU rats demonstrated similar levels of spontaneous tone [6 ± 2% (HLU) vs. 6 ± 2% (control)] and myogenic reactivity to control rats. Neither KCl-induced contractile responses (10–50 mM KCl) nor VGCC density was significantly different between mixed gastrocnemius arterioles of HLU and control rats. These results suggest that HLU produces diverse adaptations in myogenic reactivity of arterioles isolated from different fiber-type regions of a single skeletal muscle. Furthermore, alterations in myogenic responses were not attributable to altered VGCC density.

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