Pulsation-induced dilation of subendocardial and subepicardial arterioles: effect on vasodilator sensitivity

2002 ◽  
Vol 282 (1) ◽  
pp. H311-H319 ◽  
Author(s):  
Oana Sorop ◽  
Jos A. E. Spaan ◽  
Ed VanBavel
Keyword(s):  
Blood Flow ◽  
Intracellular Calcium ◽  
Pressure Pulsation ◽  
Coronary Vessels ◽  
Resistance Arteries ◽  
Fura 2 ◽  
Compression Effect ◽  
Steady Pressure

Coronary vessels are squeezed by the surrounding myocardium during systole, impeding blood flow specifically in the subendocardium. To study the myocardial compression effect, we applied pulsatile transvascular pressure to isolated, cannulated subendocardial (Endo) and subepicardial (Epi) resistance arteries. Pressure pulsation at 0.5 to 2.5 Hz between 20 and 100 mmHg induced dilation of preconstricted vessels that was somewhat larger in Epi arterioles. In four Epi and five Endo arterioles loaded with fura 2, pulsation led to a small increase in intracellular calcium. Pulsation induced a significant decrease in IC50for bradykinin (BK) (5.9 ± 0.6 vs. 27.3 ± 3.2 nM in Epi vessels and 7.6 ± 0.3 vs. 302 ± 9 nM in Endo vessels), compared with steady pressure. The adenosine (Ado) sensitivity was not significantly affected (2.21 ± 0.08 vs. 3.76 ± 0.4 μM) in Epi arteries but was enhanced during pulsations in Endo vessels (3.1 ± 0.3 vs. 10.1 ± 0.6 μM). When pulsation-induced dilation was compensated by a higher concentration of the preconstrictor (U-46619), a significantly larger dilation to BK or Ado was found during pulsations. In conclusion, pulsation-induced dilation occurs at physiologically relevant frequencies and amplitudes in Endo vessels. The process does not involve intracellular calcium reduction and increases vasodilator sensitivity.

Increased Aggregation and Secretion Responses of Human Platelets when Loaded with the Calcium Fluorescent Probes Quin2 and Fura-2

1987 ◽  
Vol 58 (02) ◽  
pp. 737-743 ◽  
Author(s):  
Frarnçois Lanza ◽  
Alain Beretz ◽  
Martial Kubina ◽  
Jean-Pierre Cazenave
Keyword(s):  
Intracellular Calcium ◽  
Shape Change ◽  
Calcium Ionophore ◽  
Human Platelets ◽  
Arachidonic Acid Metabolism ◽  
Free Calcium ◽  
Membrane Bilayer ◽  
Fluorescent Indicators ◽  
Fura 2 ◽  
Low Concentrations

SummaryIncorporation into human platelets of the calcium fluorescent indicators quin2 or fura-2 at low concentrations used to measure intracellular free calcium leads to the potentiation of the effects of agonists on platelets. This was shown by increased aggregatory and secretory responses of quin2 or fura-2 loaded platelets after stimulation with ADP, PAP and with low concentrations of thrombin, collagen, the endoperoxide analog U-46619 and the calcium ionophore A 23187. Quin2 and fura-2 mediated platelet sensitisation could be due to altered arachidonic acid metabolism since it was inhibited by prior treatment with the cydooxygenase inhibitor acetylsalicylate. In contrast, platelets loaded with higher concentrations of calcium chelators exhibited diminished aggregation responses to all aggregating agents. This latter effect was accompanied by increased fluidity of the platelet plasma membrane bilayer and by the exposure of a new pool of membranes to the outer surface of platelets, as monitored with trimethylammonium- diphenylhexatriene (TMA-DPH) in platelets loaded with the non-fluorescent calcium probe analog MAPT. In contrast, low concentrations of quin2 did not potentiate shape change of platelets activated with ADP. Thus, shape change and aggregation can be influenced separately by intracellular Ca2+ chelators. We conclude that platelet responses are altered by the incorporation of intracellular calcium chelators at concentrations used to monitor intracellular calcium changes.

Cultured olfactory interneurons from Limax maximus: optical and electrophysiological studies of transmitter-evoked responses

1993 ◽  
Vol 69 (6) ◽  
pp. 1940-1947 ◽  
Author(s):  
L. D. Rhines ◽  
P. G. Sokolove ◽  
J. Flores ◽  
D. W. Tank ◽  
A. Gelperin
Keyword(s):  
Action Potential ◽  
Intracellular Calcium ◽  
Local Field ◽  
Local Field Potential ◽  
Field Potential ◽  
Optical Measurements ◽  
Optical Studies ◽  
Isolated Cells ◽  
Fura 2 ◽  
Limax Maximus

1. The olfactory processing network in the procerebral (PC) lobe of the terrestrial mollusk Limax maximus exhibits a coherent oscillation of local field potential that is modulated by odor input. To understand the cellular basis of this oscillation, we developed a cell culture preparation of isolated PC neurons and studied the responses of isolated cells to stimulation with neurotransmitters known to be present in the PC lobe. 2. The distribution of PC soma diameters suggests at least two different populations of neurons. Approximately 95% of isolated cells had soma diameters of 7-8 microns, with the remaining cells having larger diameters (10-15 microns). 3. Extracellular measurements of action potentials and optical measurements of intracellular calcium concentrations in fura-2-loaded cells were made. Serotonin and dopamine excited PC neurons and promoted transitions from steady to bursty activity. Both amines elicited increases in intracellular calcium, presumably concomitant with the increase in action-potential frequency. 4. Glutamate suppressed action-potential firing and reduced intracellular calcium. This effect was seen most clearly when glutamate was applied to cells excited by high potassium medium. Quisqualate is an effective glutamate agonist in this system, whereas kainate is not. 5. Combined with anatomic and biochemical data and with studies of the effects of these neurotransmitters on the oscillating local field potential of the intact PC network, the data from isolated PC neurons are consistent with the hypothesis that dopamine and serotonin modulate network dynamics, whereas glutamate is involved in generating the basic oscillation of local field potential in the PC. 6. The optical studies of fura-2-loaded cells showed that several treatments that increase the rate of action-potential production lead to elevations in intracellular calcium. Optical studies of intracellular calcium may be useful for multisite measurements of activity in the intact, oscillating PC lobe network.

Mechanisms of Direct Inhibitory Action of Isoflurane on Vascular Smooth Muscle of Mesenteric Resistance Arteries

2003 ◽  
Vol 99 (3) ◽  
pp. 666-677 ◽  
Author(s):  
Takashi Akata ◽  
Tomoo Kanna ◽  
Jun Yoshino ◽  
Shosuke Takahashi
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Vascular Reactivity ◽  
Channel Blocker ◽  
Isometric Force ◽  
Systemic Resistance ◽  
Resistance Arteries ◽  
Voltage Gated ◽  
Fura 2 ◽  
Force Relation

Background Isoflurane has been shown to directly inhibit vascular reactivity. However, less information is available regarding its underlying mechanisms in systemic resistance arteries. Methods Endothelium-denuded smooth muscle strips were prepared from rat mesenteric resistance arteries. Isometric force and intracellular Ca2+ concentration ([Ca2+]i) were measured simultaneously in the fura-2-loaded strips, whereas only the force was measured in the beta-escin membrane-permeabilized strips. Results Isoflurane (3-5%) inhibited the increases in both [Ca2+]i and force induced by either norepinephrine (0.5 microM) or KCl (40 mM). These inhibitions were similarly observed after depletion of intracellular Ca2+ stores by ryanodine. Regardless of the presence of ryanodine, after washout of isoflurane, its inhibition of the norepinephrine response (both [Ca2+]i and force) was significantly prolonged, whereas that of the KCl response was quickly restored. In the ryanodine-treated strips, the norepinephrine- and KCl-induced increases in [Ca2+]i were both eliminated by nifedipine, a voltage-gated Ca2+ channel blocker, whereas only the former was inhibited by niflumic acid, a Ca2+-activated Cl- channel blocker. Isoflurane caused a rightward shift of the Ca2+-force relation only in the fura-2-loaded strips but not in the beta-escin-permeabilized strips. Conclusions In mesenteric resistance arteries, isoflurane depresses vascular smooth muscle reactivity by directly inhibiting both Ca2+ mobilization and myofilament Ca2+ sensitivity. Isoflurane inhibits both norepinephrine- and KCl-induced voltage-gated Ca2+ influx. During stimulation with norepinephrine, isoflurane may prevent activation of Ca2+-activated Cl- channels and thereby inhibit voltage-gated Ca2+ influx in a prolonged manner. The presence of the plasma membrane appears essential for its inhibition of the myofilament Ca2+ sensitivity.

The distribution of intracellular calcium chelator (fura-2) in a population of intact human red cells

1993 ◽  
Vol 1148 (1) ◽  
pp. 152-156 ◽  
Author(s):  
Virgilio L. Lew ◽  
Zipora Etzion ◽  
Robert M. Bookchin ◽  
Rui daCosta ◽  
Heikki Väänänen ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Red Cells ◽  
Fura 2 ◽  
Human Red Cells

Abstract 632: Flow-induced TRPV4 Activation Mediates Calcium Influx In The Thick Ascending Limb.

Hypertension ◽  
2012 ◽  
Vol 60 (suppl_1) ◽  
Author(s):  
Pablo D Cabral ◽  
Jeffrey L Garvin
Keyword(s):  
Blood Pressure ◽  
Intracellular Calcium ◽  
Calcium Influx ◽  
Ruthenium Red ◽  
Sodium Balance ◽  
Transient Receptor Potential Vanilloid ◽  
No Production ◽  
Thick Ascending Limb ◽  
Fura 2 ◽  
Luminal Flow

Background: The thick ascending limb is critical in the regulation of sodium balance and therefore blood pressure. We previously showed that nitric oxide (NO), which inhibits sodium chloride transport and therefore blood pressure is regulated by luminal flow in this segment. Transient receptor potential vanilloid 4 (TRPV4), a member of the TRPV family of cation channels, is expressed in the thick ascending limb. This calcium permeable channel can be activated by luminal flow in other cell types. Therefore, we hypothesized that in the thick ascending limb luminal flow induces TRPV4 activation thereby increasing calcium influx and NO production. METHODS: We used the TRPV4 antagonists Ruthenium red and RN 1734 and the TRPV4 agonist GSK1016790A and measured intracellular calcium and NO production in the absence and presence of luminal flow in isolated and perfused thick ascending limbs from Sprague Dawley rats. NO production was measured using the NO-sensitive dye DAF FM da. Intracellular calcium was measured using the ratiometric calcium sensitive dye Fura-2 AM. Results: Increasing luminal flow from 0 to 20 nL/min stimulated NO production from 8 ± 3 to 45 ± 12 arbitrary units (AU)/min ( p <0.05, n =5). Increasing luminal flow in the presence of the TRPV4 antagonist Ruthenium red (15 μM) eliminated NO production (from 18 ± 5 to 16 ± 9 AU/min; n = 4). Flow-induced NO production was also prevented by the selective TRPV4 antagonist RN 1734 (10 μM) (from 11 ± 7 to 9 ± 2 AU/min; n = 4). Increasing luminal flow increased Fura 2 ratio units by 113 ± 20 %. However, in the presence of the TRPV4 antagonist Ruthenium red (15 μM) Fura 2 ratio units increased only by 55 ± 12 % in response to luminal flow ( p <0.04, n =6). In the absence of luminal flow, activating TRPV4 using the TRPV4 selective agonist GSK1016790A (1 ηM) increased Fura 2 ratio units by 204 ± 43 %. Conclusion: From these data we conclude that flow-induced TRPV4 activation mediates calcium influx and NO production in the thick ascending limb.

Cytosolic Ca2+ dynamics in hamster ascending thin limb of Henle's loop

1995 ◽  
Vol 268 (6) ◽  
pp. F1148-F1153 ◽  
Author(s):  
N. Takahashi ◽  
Y. Kondo ◽  
O. Ito ◽  
Y. Igarashi ◽  
K. Omata ◽  
...  
Keyword(s):  
Steady State ◽  
Intracellular Calcium ◽  
State Level ◽  
Steady State Level ◽  
Subsequent Reduction ◽  
Fura 2 ◽  
Henle's Loop ◽  
K Concentration ◽  
Thin Limb

Intracellular calcium plays an important role in the regulation of Cl- reabsorption in the ascending thin limb of Henle's loop (ATL). To elucidate the cytosolic Ca2+ dynamics in the ATL, intracellular Ca2+ concentration activity ([Ca2+]i) was measured in the in vitro microperfused hamster ATL using fura 2. Basal [Ca2+]i was 89.1 +/- 7.3 nM (n = 9 tubules). Removal of Ca2+ from the peritubular solution decreased [Ca2+]i from 89.1 +/- 7.3 to 64.1 +/- 7.1 nM in 2 min (n = 9, P < 0.05), whereas [Ca2+]i did not change after removal of Ca2+ from the luminal solution. Addition of 1 mM NaCN to the bath increased [Ca2+]i. This effect was completely abolished by the elimination of ambient Ca2+. Trifluoperazine and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) in the bath reversibly increased [Ca2+]i, whereas addition of 1 mM ouabain to the bath decreased [Ca2+]i. Rates of changes in [Ca2+]i after removal and replacement of basolateral Ca2+ were not affected by removal of Na+, K+, or Cl- from the bath, whereas nicardipine decreased these parameters. Increasing bath K+ from 5 to 100 mM decreased [Ca2+]i from 69.3 +/- 5.8 to 50.8 +/- 5.0 nM in 1 min (n = 6, P < 0.05). Subsequent reduction of K+ from 100 to 5 mM increased [Ca2+]i to 174.0 +/- 30.8 nM in 1 min, followed by a gradual decrease in [Ca2+]i to a steady-state level of 74.2 +/- 8.0 nM in 2 min. Changes in basolateral K+ concentration did not affect [Ca2+]i in the absence of ambient Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Axotomy induces a transient and localized elevation of the free intracellular calcium concentration to the millimolar range

1995 ◽  
Vol 74 (6) ◽  
pp. 2625-2637 ◽  
Author(s):  
N. E. Ziv ◽  
M. E. Spira
Keyword(s):  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Intracellular Calcium Concentration ◽  
Concentration Gradients ◽  
Fura 2 ◽  
Direct Demonstration ◽  
Free Intracellular Calcium ◽  
Axonal Transection ◽  
Transient Elevation

1. Axonal transection triggers a cascade of pathological processes that frequently lead to the degeneration of the injured neuron. It is generally believed that the degenerative process is triggered by an overwhelming influx of calcium through the cut end of the axon. 2. Theoretical considerations and indirect observations suggest that axotomy is followed by an increase in the free intracellular calcium concentration ([Ca2+]i) to the millimolar level. In contrast, only relatively modest and transient elevation in [Ca2+]i to the micromolar level was revealed by recent fura-2 studies. 3. In the current study we used the low-affinity Ca2+ indicator mag-fura-2 to reexamine the spatiotemporal distribution pattern of Ca2+ after axotomy and to map the free intracellular Mg2+ concentration gradients. 4. We report that axotomy elevates [Ca2+]i well beyond the "physiological" range of calcium concentrations, to levels > 1 mM near the tip of the cut axon and to hundreds of micromolars along the axon further away from the cut end. Nevertheless, [Ca2+]i recovers to the control levels within 2-3 min after the resealing of the cut end. 5. A comparison of the behavior of fura-2 and mag-fura-2 in the cytosol of the axotomized neurons reveals that the determination of [Ca2+]i by fura-2 largely underestimates the actual intracellular Ca2+ concentrations. 6. Experiments in which one branch of a bifurcated axon was transected revealed that the elevation in [Ca2+]i is confined to the transected axonal branch and does not spread beyond the bifurcation point. 7. After axotomy, the intracellular Mg2+ concentration equilibrates rapidly with the external concentration and then recovers at a rate somewhat slower than that of [Ca2+]i. 8. To the best of our knowledge, this study is the first direct demonstration that axotomy elevates [Ca2+]i to the millimolar range and that neurons are able to recover from these extreme calcium concentrations.

Neural mechanisms regulating neurohypophysial resistance arteries

1992 ◽  
Vol 263 (5) ◽  
pp. H1605-H1615
Author(s):  
D. F. Hanley ◽  
D. A. Wilson ◽  
M. A. Conway ◽  
R. J. Traystman ◽  
J. A. Bevan ◽  
...  
Keyword(s):  
Blood Flow ◽  
Vasoactive Intestinal Polypeptide ◽  
Neural Control ◽  
Neural Mechanisms ◽  
Resistance Arteries ◽  
Frequency Dependent ◽  
Arterial Circulation ◽  
Physiological Relevance ◽  
Resistance Vessels ◽  
Perivascular Nerves

We defined the extent of vasoactive intestinal polypeptide (VIP) and noradrenergic influences on isolated 100- to 200-microns-diameter vessels from the resistance arterial circulation of the neurohypophysis. A dual extracranial (inferior hypophysial) and intracranial (superior hypophysial) arterial supply to the neurohypophysis was confirmed. The inferior hypophysial artery demonstrates noradrenergic and VIP-like perivascular nerves, whereas the superior hypophysial artery shows primarily VIP-like innervation. Pharmacological sensitivity of the inferior hypophysial to VIP [mean effective dose (ED50) = 10(-8.2) M] and to norepinephrine (ED50 = 10(-5.7) M) was demonstrated. The superior hypophysial reacted only to VIP (ED50 = 10(-8.6) M). The physiological relevance of these findings was tested with transmural nerve stimulation. Frequency-dependent vasodilation of both inferior and superior hypophysial arteries was demonstrated. This dilation could not be blocked with atropine or propranolol. Frequency-dependent vasoconstriction was identified in extracranial vessels including the inferior hypophysial artery. This constriction is only partially blocked by prazosin, phentolamine, and guanethidine. When neurohypophysial resistance vessels are compared with larger circle of Willis arteries and similar-size pial vessels of other cerebral regions, they appear to have regionally unique neural mechanisms for regulating blood flow. Specifically whether controlled by periarterial nerves or other tissue influences, the inferior hypophysial artery appears to meet anatomic, pharmacological, and physiological definitions of neural control for both dilator and constrictor activities of flow to the neurohypophysis.

Bifurcation asymmetry of the porcine coronary vasculature and its implications on coronary flow heterogeneity

2004 ◽  
Vol 287 (6) ◽  
pp. H2493-H2500 ◽  
Author(s):  
Ghada Kalsho ◽  
Ghassan S. Kassab
Keyword(s):  
Blood Flow ◽  
Coronary Vessels ◽  
Significant Heterogeneity ◽  
Branching Pattern ◽  
Optical Sectioning ◽  
Coronary Vasculature ◽  
Coronary Veins ◽  
Flow Heterogeneity ◽  
Small Vessels ◽  
Arteries And Veins

The branching pattern of the coronary arteries and veins is asymmetric, i.e., many small vessels branch off of a large trunk such that the two daughter vessels at a bifurcation are of unequal diameters and lengths. One important implication of the geometric vascular asymmetry is the dispersion of blood flow at a bifurcation, which leads to large spatial heterogeneity of myocardial blood flow. To document the asymmetric branching pattern of the coronary vessels, we computed an asymmetry ratio for the diameters and lengths of all vessels, defined as the ratio of the daughter diameters and lengths, respectively. Previous data from silicone elastomer cast of the entire coronary vasculature including arteries, arterioles, venules, and veins were analyzed. Data on smaller vessels were obtained from histological specimens by optical sectioning, whereas data on larger vessels were obtained from vascular casts. Asymmetry ratios for vascular areas, volumes, resistances, and flows of the various daughter vessels were computed from the asymmetry ratios of diameters and lengths for every order of mother vessel. The results show that the largest orders of arterial and venous vessels are most asymmetric and the degree of asymmetry decreases toward the smaller vessels. Furthermore, the diameter asymmetry at a bifurcation is significantly larger for the coronary veins (1.7–6.8 for sinus veins) than the corresponding arteries (1.5–5.8 for left anterior descending coronary artery) for orders 2–10, respectively. The reported diameter asymmetry at a bifurcation leads to significant heterogeneity of blood flow at a bifurcation. Hence, the present data quantify the dispersion of blood flow at a bifurcation and are essential for understanding flow heterogeneity in the coronary circulation.

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