Ca2+ sensitivity of isolated arterioles from the hamster cheek pouch

1991 ◽  
Vol 260 (2) ◽  
pp. H355-H361 ◽  
Author(s):  
M. R. Hynes ◽  
B. R. Duling
Keyword(s):  
Smooth Muscle ◽  
Muscle Layer ◽  
Cheek Pouch ◽  
Maximum Diameter ◽  
Maximal Response ◽  
Bathing Solution ◽  
Hamster Cheek Pouch ◽  
Mean Time ◽  
Concentration Response Curve

When isolated from the hamster cheek pouch, cannulated, and perfused, 60- to 90-microns arterioles spontaneously contracted to 67 +/- 4% of maximum diameter. Vessel sensitivity to variations in extracellular Ca2+ was then evaluated. Tone, regardless of its source, was highly dependent on the concentration of Ca2+ in the bathing solution. The magnitude of responses to changing Ca2+ depended upon which vessel surface (luminal or abluminal) the change was made. For K(+)-induced tone the Ca2+ concentration-response curve was right shifted 60-fold for luminal vs. abluminal changes. These results suggest that restricted diffusion of Ca2+ from lumen to smooth muscle dramatically reduces smooth muscle Ca2+ concentration and that under standard in vitro conditions the smooth muscle layer is effectively isolated from luminal contents. Both the cytosolic and stored Ca2+ in these microvessels were dependent on the Ca2+ concentration in the bathing solution. Abrupt removal of Ca2+ from bath produced a rapid maximal dilation with a mean time to half-maximal response (t1/2 max) of 14 +/- 4 s. Ca2+ replacement induced a return to the previous level of tone with a mean t1/2 max of 8 +/- 3 s. The magnitude of transient responses to caffeine (10 mM) was inversely related to the time of exposure to zero Ca2+ with a rapid decay in magnitude (t1/2 max = 2.7 +/- 0.8 min). These data suggest that the smooth muscle cells of arterioles have a particularly rapid transmembrane Ca2+ flux that is tightly controlled by an intracellular regulatory mechanism, which may explain the generally increased dependence of smaller vessels on extracellular Ca2+.

Force-velocity relationship of myogenically active arterioles

2002 ◽  
Vol 282 (1) ◽  
pp. H165-H174 ◽  
Author(s):  
Michael J. Davis ◽  
Judy Davidson
Keyword(s):  
Smooth Muscle ◽  
Maximum Velocity ◽  
Cheek Pouch ◽  
Myogenic Tone ◽  
Internal Diameter ◽  
Wall Tension ◽  
Shortening Velocity ◽  
Hamster Cheek Pouch ◽  
Velocity Of Shortening

We compared the shortening velocity of smooth muscle in arterioles that had low or high levels of myogenic tone or norepinephrine (NE)-induced tone. We hypothesized that enhanced myogenic tone of arterioles reflects an enhanced maximum velocity of shortening of arteriolar smooth muscle in a way that is different from that produced by NE. These concepts are untested assumptions of arteriolar mechanics. Second-order arterioles from hamster cheek pouch (passive diameter at 40 mmHg = 42 μm) were isolated and cannulated for in vitro study. In the absence of flow, pressure was controlled by hydraulic pumps so that servo control of wall tension could be achieved from measurement of internal diameter and pressure. Isotonic quick-release protocols were used to measure the initial velocity of shortening following release from control wall tension (afterload) to a series of fractional afterloads. After release, the initial rates of shortening were fit to the Hill equation to obtain coefficients for a hyperbolic fit of the velocity-afterload relationship. The maximal unloaded shortening velocity for partially activated arterioles ( V′max) was determined from the y-intercept of each plot. Using this procedure, we compared V′max from two groups of arterioles equilibrated at low or high pressure, i.e., with low or high myogenic tone. Arterioles with higher myogenic tone had higher values of V′max than arterioles with lower myogenic tone. V′max for arterioles partially activated with NE at low pressure was comparable to V′max for arterioles with high myogenic tone, but NE produced high velocities at low force, whereas enhanced myogenic tone produced roughly parallel shifts in velocity and force. The results suggest that increased myogenic tone does indeed reflect enhanced activation of arteriolar smooth muscle, and this effect is mechanically different from that produced by NE.

Arteriolar smooth muscle Ca2+ dynamics during blood flow control in hamster cheek pouch

2006 ◽  
Vol 101 (1) ◽  
pp. 307-315 ◽  
Author(s):  
Johan Fredrik Brekke ◽  
William F. Jackson ◽  
Steven S. Segal
Keyword(s):  
Blood Flow ◽  
Smooth Muscle ◽  
Local Control ◽  
Cheek Pouch ◽  
Tissue Blood Flow ◽  
Hamster Cheek Pouch ◽  
Dye Loading ◽  
Blood Flow Control

Intracellular calcium concentration ([Ca2+]i) governs the contractile status of arteriolar smooth muscle cells (SMC). Although studied in vitro, little is known of SMC [Ca2+]i dynamics during the local control of blood flow. We tested the hypothesis that the rise and fall of SMC [Ca2+]i underlies arteriolar constriction and dilation in vivo. Aparenchymal segments of second-order arterioles (diameter 35 ± 2 μm) were prepared in the superfused cheek pouch of anesthetized hamsters ( n = 18) and perifused with the ratiometric dye fura PE-3 (AM) to load SMC (1 μM, 20 min). Resting SMC [Ca2+]i was 406 ± 37 nM. Elevating superfusate O2 from 0 to 21% produced constriction (11 ± 2 μm) that was unaffected by dye loading; [Ca2+]i increased by 108 ± 53 nM ( n = 6, P < 0.05). Cycling of [Ca2+]i during vasomotion (amplitude, 150 ± 53 nM; n = 4) preceded corresponding diameter changes (7 ± 1 μm) by ∼2 s. Microiontophoresis (1 μm pipette tip; 1 μA, 1 s) of phenylephrine (PE) transiently increased [Ca2+]i by 479 ± 64 nM ( n = 8, P < 0.05) with constriction (26 ± 3 μm). Flushing blood from the lumen with saline increased fluorescence at 510 nm by ∼45% during excitation at both 340 and 380 nm with no difference in resting [Ca2+]i, diameter or respective responses to PE ( n = 7). Acetylcholine microiontophoresis (1 μA, 1 s) transiently reduced resting SMC [Ca2+]i by 131 ± 21 nM ( n = 6, P < 0.05) with vasodilation (17 ± 1 μm). Superfusion of sodium nitroprusside (10 μM) transiently reduced SMC [Ca2+]i by 124 ± 18 nM ( n = 6, P < 0.05), whereas dilation (23 ± 5 μm) was sustained. Resolution of arteriolar SMC [Ca2+]i in vivo discriminates key signaling events that govern the local control of tissue blood flow.

Resolution of smooth muscle and endothelial pathways for conduction along hamster cheek pouch arterioles

2000 ◽  
Vol 278 (2) ◽  
pp. H604-H612 ◽  
Author(s):  
Iain S. Bartlett ◽  
Steven S. Segal
Keyword(s):  
Smooth Muscle ◽  
Muscle Layer ◽  
Endothelial Damage ◽  
Cheek Pouch ◽  
Hamster Cheek Pouch ◽  
Central Segment ◽  
Proximal Site ◽  
Arteriolar Wall ◽  
Distal Site

In the cheek pouch of anesthetized male hamsters, microiontophoresis of Ach (endothelium-dependent vasodilator) or phenylephrine (PE; smooth muscle-specific vasoconstrictor) onto an arteriole (resting diameter, 30–40 μm) evokes vasodilation or vasoconstriction (amplitude, 15–25 μm), respectively, that conducts along the arteriolar wall. In previous studies of conduction, endothelial and smooth muscle layers of the arteriolar wall have remained intact. We tested whether selective damage to endothelium or to smooth muscle would disrupt the initiation and conduction of vasodilation or vasoconstriction. Luminal (endothelial) or abluminal (smooth muscle) light-dye damage was produced within an arteriolar segment centered 500 μm upstream from the distal site of stimulation; conducted responses (amplitude, 10–15 μm) were observed at a proximal site located 1,000 μm upstream. Endothelial damage abolished local responses to ACh in the central segment without affecting those to PE. Nevertheless, ACh delivered at the distal site evoked vasodilation that conducted through the central segment and appeared unhindered at the proximal site. Smooth muscle damage inhibited responses to PE in the central segment and abolished the conduction of vasoconstriction but did not affect conducted vasodilation. We suggest that for cheek pouch arterioles in vivo, vasoconstriction to PE is initiated and conducted within the smooth muscle layer alone. In contrast, once vasodilation to ACh is initiated via intact endothelial cells, the signal is conducted along smooth muscle as well as endothelial cell layers.

Cellular pathways of the conducted electrical response in arterioles of hamster cheek pouch in vitro

1995 ◽  
Vol 269 (6) ◽  
pp. H2031-H2038 ◽  
Author(s):  
J. Xia ◽  
T. L. Little ◽  
B. R. Duling
Keyword(s):  
Electrical Response ◽  
Electrical Current ◽  
Cell Types ◽  
Cheek Pouch ◽  
Resting Membrane Potential ◽  
Hamster Cheek Pouch ◽  
Cellular Pathways ◽  
Current Flows ◽  
Electrical Responses

We have previously shown that conducted vasomotor responses follow patterns that are consistent with a passive spread of electrical current along the length of the arterioles [(Xia and Duling, Am. J. Physiol. 269 (Heart Circ. Physiol. 38): H2022-H2030, 1995]. In this study, we define the cells through which the current flows. Isolated arterioles of hamster cheek pouch were used. The mean resting membrane potential (RMP) for randomly sampled arteriolar cells was -67 mV. When cell types were identified by dye injection, the RMPs were -68 and -67 mV for smooth muscle (SM) and endothelium (EC), respectively. Pulses of KCl induced transient, monophasic depolarizations at the site of stimulation (local), which were conducted decrementally along the length of the arteriole over several millimeters. During electrical conduction, three patterns of responses could be observed, but identical patterns of the conducted electrical responses were always observed in SM and EC. Phenylephrine stimulation also caused transient local and conducted depolarizations in both SM and EC. As with KCl stimuli, shapes of conducted electrical responses were identical in records made in both cell types. The results suggest that SM and EC are electrically coupled both homocellularly and heterocellularly.

Length-tension relationship of vascular smooth muscle in single arterioles

1989 ◽  
Vol 256 (3) ◽  
pp. H630-H640 ◽  
Author(s):  
M. J. Davis ◽  
R. W. Gore
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Wall Stress ◽  
Physiological Saline ◽  
Intraluminal Pressure ◽  
Cheek Pouch ◽  
Hamster Cheek Pouch ◽  
Longitudinal Response ◽  
Physiological Saline Solution ◽  
Relationship Of

Longitudinal response gradients in the microcirculation may in part be explained in terms of the length-tension relationship of vascular smooth muscle at different points along the vascular tree. To test this hypothesis, four branching orders of arterial vessels (20-80 microns ID) were dissected from the hamster cheek pouch and cannulated with concentric micropipettes. Intraluminal pressure was monitored with a servo-null micropipette, and arteriolar dimensions were measured using a videomicrometer. All arterioles developed spontaneous tone in physiological saline solution. Pressure-diameter curves were recorded for maximally activated vessels and for passive vessels. Maximal active wall tension varied nearly threefold, but maximal active medial wall stress (approximately 4 x 10(6) dyn/cm2) varied only approximately 20% between the different vessel orders. These data support the concept that smooth muscle cells from vessels of different sizes are mechanically similar but do not completely explain the longitudinal response gradients reported in the cheek pouch microcirculation. An analysis of the effect of arteriolar wall buckling suggests that the luminal folds that develop at short vessel radii may broaden the peak of the active stress-length curve and extend the pressure range over which arterioles are most sensitive to physical and chemical stimuli.

Phospholipids modulate the biophysical properties and vasoactivity of PACAP-(1—38)

2002 ◽  
Vol 93 (4) ◽  
pp. 1377-1383 ◽  
Author(s):  
Takaya Tsueshita ◽  
Salil Gandhi ◽  
Hayat Önyüksel ◽  
Israel Rubinstein
Keyword(s):  
Conformational Transition ◽  
Critical Micellar Concentration ◽  
Random Coil ◽  
Cheek Pouch ◽  
Hamster Cheek Pouch ◽  
Pituitary Adenylate Cyclase ◽  
Peripheral Microcirculation ◽  
Α Helix

The purpose of this study was to elucidate the interactions between pituitary adenylate cyclase-activating peptide (PACAP)-(1—38) and phospholipids in vitro and to determine whether these phenomena modulate, in part, the vasorelaxant effects of the peptide in the intact peripheral microcirculation. We found that the critical micellar concentration of PACAP-(1—38) was 0.4–0.9 μM. PACAP-(1—38) significantly increased the surface tension of a dipalmitoylphosphatidylcholine monolayer and underwent conformational transition from predominantly random coil in saline to α-helix in the presence of distearoyl-phosphatidylethanolamine-polyethylene glycol (molecular mass of 2,000 Da) sterically stabilized phospholipid micelles (SSM) ( P < 0.05). Using intravital microscopy, we found that aqueous PACAP-(1—38) evoked significant concentration-dependent vasodilation in the intact hamster cheek pouch that was significantly potentiated when PACAP-(1—38) was associated with SSM ( P < 0.05). The vasorelaxant effects of aqueous PACAP-(1—38) were mediated predominantly by PACAP type 1 (PAC1) receptors, whereas those of PACAP-(1—38) in SSM predominantly by PACAP/vasoactive intestinal peptide type 1 and 2 (VPAC1/VPAC2) receptors. Collectively, these data indicate that PACAP-(1—38) self-associates and interacts avidly with phospholipids in vitro and that these phenomena amplify peptide vasoactivity in the intact peripheral microcirculation.

Release of epithelium-derived PGE2 from canine trachea after antigen inhalation

1998 ◽  
Vol 274 (2) ◽  
pp. L220-L225 ◽  
Author(s):  
I. McGrogan ◽  
L. J. Janssen ◽  
J. Wattie ◽  
P. M. O’Byrne ◽  
E. E. Daniel
Keyword(s):  
Smooth Muscle ◽  
Electrical Field Stimulation ◽  
Tracheal Smooth Muscle ◽  
Organ Bath ◽  
Field Stimulation ◽  
Electrical Field ◽  
Concentration Response Curve

To investigate the role of prostaglandin (PG) E2 in allergen-induced hyperresponsiveness, dogs inhaled either the allergen Ascaris suum or vehicle (Sham). Twenty-four hours after inhalation, some animals exposed to allergen demonstrated an increased responsiveness to acetylcholine challenge in vivo (Hyp-Resp), whereas others did not (Non-Resp). Strips of tracheal smooth muscle, either epithelium intact or epithelium denuded, were suspended on stimulating electrodes, and a concentration-response curve to carbachol (10−9 to 10−5 M) was generated. Tissues received electrical field stimulation, and organ bath fluid was collected to determine PGE2content. With the epithelium present, all three groups contracted similarly to 10−5 M carbachol, whereas epithelium-denuded tissues from animals that inhaled allergen contracted more than tissues from Sham dogs. In response to electrical field stimulation, Hyp-Resp tissues contracted less than Sham tissues in the presence of epithelium and more than Sham tissues in the absence of epithelium. PGE2release in the muscle bath was greater in Non-Resp tissues than in Sham or Hyp-Resp tissues when the epithelium was present. Removal of the epithelium greatly inhibited PGE2release. We conclude that tracheal smooth muscle is hyperresponsive in vitro after in vivo allergen exposure only when the modulatory effect of the epithelium, largely through PGE2 release, is removed.

Origin of Motion in the Human Ureter: Mechanics, Energetics and Kinetics of the Myosin Molecular Motors

2012 ◽  
Vol 79 (2) ◽  
pp. 123-129 ◽  
Author(s):  
Romina Vargiu ◽  
Anna Perinu ◽  
Antonello De Lisa ◽  
Frank Tintrup ◽  
Francesco Manca ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Molecular Motors ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Shortening Velocity ◽  
Smooth Muscle Layer ◽  
Circular Smooth Muscle ◽  
Longitudinal Smooth Muscle ◽  
Human Ureter

Background Ureteral peristalsis is the result of coordinated mechanical motor performance of longitudinal and circular smooth muscle layer of the ureter wall. The main aim of this study was to characterize in smooth muscle of proximal segments of human ureter, the mechanical properties at level of muscle tissue and at level of myosin molecular motors. Methods Ureteral samples were collected from 15 patients, who underwent nephrectomy for renal cancer. Smooth muscle strips longitudinally and circularly oriented from proximal segments of human ureter were used for the in vitro experiments. Mechanical indices including the maximum unloaded shortening velocity (Vmax), and the maximum isometric tension (P0) normalized per cross-sectional area, were determined in vitro determined in electrically evoked contractions of longitudinal and circular smooth muscle strips. Myosin cross-bridge (CB) number per mm2 (Ψ) the elementary force per single CB (Ψ) and kinetic parameters were calculated in muscle strips, using Huxley's equations adapted to nonsarcomeric muscles. Results Longitudinal smooth muscle strips exhibited a significantly (p<0.05) faster Vmax (63%) and a higher P0 (40%), if compared to circular strips. Moreover, longitudinal muscle strips showed a significantly higher unitary force (Ψ) per CB. However, no significant differences were observed in CB number, the attachment (f1) and the detachment (g2) rate constants between longitudinal and circular muscle strips. Conclusions The main result obtained in the present work documents that the mechanical, energetic and unitary forces per CB of longitudinal layer of proximal ureter are better compared to the circular one; these preliminary findings suggested, unlike intestinal smooth muscle, a major role of longitudinal smooth muscle layer in the ureter peristalsis.

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