1
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Fry BC, Secomb TW. Distinct roles of red-blood-cell-derived and wall-derived mechanisms in metabolic regulation of blood flow. Microcirculation 2021; 28:e12690. [PMID: 33650127 DOI: 10.1111/micc.12690] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 02/22/2021] [Indexed: 11/26/2022]
Abstract
OBJECTIVE A theoretical model is used to analyze combinations of RBC-derived and wall-derived (RBC-independent) mechanisms for metabolic blood flow regulation, with regard to their oxygen transport properties. METHODS Heterogeneous microvascular network structures are derived from observations in rat mesentery and hamster cremaster. The effectiveness of metabolic blood flow regulation using combinations of RBC-dependent and RBC-independent mechanisms is simulated in these networks under conditions of reduced oxygen delivery and increased oxygen demand. RESULTS Metabolic regulation by a wall-derived mechanism results in higher predicted total blood flow rate and number of flowing vessels, and lower tissue hypoxic fraction, than regulation by combinations of RBC-derived and wall-derived signals. However, a combination of RBC-derived and wall-derived signals results in a higher predicted median tissue PO2 than either mechanism acting alone. CONCLUSIONS Model results suggest complementary roles for RBC-derived and wall-derived mechanisms of metabolic flow regulation, with the wall-derived mechanism responsible for avoiding hypoxia, and the RBC-derived mechanism responsible for maintaining PO2 levels high enough for optimal tissue function.
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Affiliation(s)
- Brendan C Fry
- Department of Mathematics and Statistics, Metropolitan State University of Denver, Denver, CO, USA
| | - Timothy W Secomb
- Department of Physiology, University of Arizona, Tucson, AZ, USA
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2
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Roy TK, Secomb TW. Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function. Microcirculation 2020; 28:e12673. [PMID: 33236393 DOI: 10.1111/micc.12673] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 11/17/2020] [Indexed: 12/14/2022]
Abstract
Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.
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Affiliation(s)
- Tuhin K Roy
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA
| | - Timothy W Secomb
- Department of Physiology, University of Arizona, Tucson, AZ, 85724, USA
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3
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Smit B, Smulders YM, Eringa EC, Gelissen HPMM, Girbes ARJ, de Grooth HJS, Schotman HHM, Scheffer PG, Oudemans-van Straaten HM, Spoelstra-de Man AME. Hyperoxia does not affect oxygen delivery in healthy volunteers while causing a decrease in sublingual perfusion. Microcirculation 2018; 25. [PMID: 29210137 PMCID: PMC5838560 DOI: 10.1111/micc.12433] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 11/27/2017] [Indexed: 12/17/2022]
Abstract
Objective To determine the human dose‐response relationship between a stepwise increase in arterial oxygen tension and its associated changes in DO2 and sublingual microcirculatory perfusion. Methods Fifteen healthy volunteers breathed increasing oxygen fractions for 10 minutes to reach arterial oxygen tensions of baseline (breathing air), 20, 40, 60 kPa, and max kPa (breathing oxygen). Systemic hemodynamics were measured continuously by the volume‐clamp method. At the end of each period, the sublingual microcirculation was assessed by SDF. Results Systemic DO2 was unchanged throughout the study (Pslope = .8). PVD decreased in a sigmoidal fashion (max −15% while breathing oxygen, SD18, Pslope = .001). CI decreased linearly (max −10%, SD10, Pslope < .001) due to a reduction in HR (max −10%, SD7, Pslope = .009). There were no changes in stroke volume or MAP. Most changes became apparent above an arterial oxygen tension of 20 kPa. Conclusions In healthy volunteers, supraphysiological arterial oxygen tensions have no effect on systemic DO2. Sublingual microcirculatory PVD decreased in a dose‐dependent fashion. All hemodynamic changes appear negligible up to an arterial oxygen tension of 20 kPa.
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Affiliation(s)
- Bob Smit
- Department of Intensive Care, VU University Medical Center, Amsterdam, The Netherlands
| | - Yvo M Smulders
- Department of Internal Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Etto C Eringa
- Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
| | - Harry P M M Gelissen
- Department of Intensive Care, VU University Medical Center, Amsterdam, The Netherlands
| | - Armand R J Girbes
- Department of Intensive Care, VU University Medical Center, Amsterdam, The Netherlands
| | - Harm-Jan S de Grooth
- Department of Intensive Care, VU University Medical Center, Amsterdam, The Netherlands
| | - Hans H M Schotman
- Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands
| | - Peter G Scheffer
- Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands
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4
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Rosenblum WI. Endothelium-dependent responses in the microcirculation observed in vivo. Acta Physiol (Oxf) 2018; 224:e13111. [PMID: 29873936 DOI: 10.1111/apha.13111] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 05/19/2018] [Accepted: 06/04/2018] [Indexed: 12/17/2022]
Abstract
Endothelium-dependent responses were first demonstrated 40 years ago in the aorta. Since then, extensive research has been conducted in vitro using conductance vessels and materials derived from them. However, the microcirculation controls blood flow to vital organs and has been the focus of in vivo studies of endothelium-dependent dilation beginning immediately after the first in vitro report. Initial in vivo studies employed a light/dye technique for selectively damaging the endothelium to unequivocally prove, in vivo, the existence of endothelium-dependent dilation and in the microvasculature. Endothelium-dependent constriction was similarly proven. Endothelium-dependent agonists include acetylcholine (ACh), bradykinin, arachidonic acid, calcium ionophore A-23187, calcitonin gene-related peptide (CGRP), serotonin, histamine and endothelin-1. Normal and disease states have been studied. Endothelial nitric oxide synthase, cyclooxygenase and cytochrome P450 have been shown to generate the mediators of the responses. Some of the key enzyme systems generate reactive oxygen species (ROS) like superoxide which may prevent EDR. However, one ROS, namely H2 O2 , is one of a number of hyperpolarizing factors that cause dilation initiated by endothelium. Depending upon microvascular bed, a single agonist may use different pathways to elicit an endothelium-dependent response. Interpretation of studies using inhibitors of eNOS is complicated by the fact that these inhibitors may also inhibit ATP-sensitive potassium channels. Other in vivo observations of brain arterioles failed to establish nitric oxide as the mediator of responses elicited by CGRP or by ACh and suggest that a nitrosothiol may be a better fit for the latter.
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Affiliation(s)
- W. I. Rosenblum
- Department of Pathology; Icahn School of Medicine at Mt Sinai NYC; New York NY USA
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5
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Smit B, Smulders YM, Eringa EC, Oudemans - van Straaten HM, Girbes ARJ, Wever KE, Hooijmans CR, Spoelstra - de Man AME. Effects of hyperoxia on vascular tone in animal models: systematic review and meta-analysis. Crit Care 2018; 22:189. [PMID: 30075723 PMCID: PMC6091089 DOI: 10.1186/s13054-018-2123-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 07/09/2018] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Arterial hyperoxia may induce vasoconstriction and reduce cardiac output, which is particularly undesirable in patients who already have compromised perfusion of vital organs. Due to the inaccessibility of vital organs in humans, vasoconstrictive effects of hyperoxia have primarily been studied in animal models. However, the results of these studies vary substantially. Here, we investigate the variation in magnitude of the hyperoxia effect among studies and explore possible sources of heterogeneity, such as vascular region and animal species. METHOD Pubmed and Embase were searched for eligible studies up to November 2017. In vivo and ex vivo animal studies reporting on vascular tone changes induced by local or systemic normobaric hyperoxia were included. Experiments with co-interventions (e.g. disease or endothelium removal) or studies focusing on lung, brain or fetal vasculature or the ductus arteriosus were not included. We extracted data pertaining to species, vascular region, blood vessel characteristics and method of hyperoxia induction. Overall effect sizes were estimated with a standardized mean difference (SMD) random effects model. RESULTS We identified a total of 60 studies, which reported data on 67 in vivo and 18 ex vivo experiments. In the in vivo studies, hyperoxia caused vasoconstriction with an SMD of - 1.42 (95% CI - 1.65 to - 1.19). Ex vivo, the overall effect size was SMD - 0.56 (95% CI - 1.09 to - 0.03). Between-study heterogeneity (I2) was high for in vivo (72%, 95% CI 62 to 85%) and ex vivo studies (86%, 95% CI 78 to 98%). In vivo, in comparison to the overall effect size, hyperoxic vasoconstriction was less pronounced in the intestines and skin (P = 0.03) but enhanced in the cremaster muscle region (P < 0.001). Increased constriction was seen in vessels 15-25 μm in diameter. Hyperoxic constriction appeared to be directly proportional to oxygen concentration. For ex vivo studies, heterogeneity could not be explained with subgroup analysis. CONCLUSION The effect of hyperoxia on vascular tone is substantially higher in vivo than ex vivo. The magnitude of the constriction is most pronounced in vessels ~ 15-25 μm in diameter and is proportional to the level of hyperoxia. Relatively increased constriction was seen in muscle vasculature, while reduced constriction was seen in the skin and intestines.
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Affiliation(s)
- Bob Smit
- Department of Intensive Care, VU University Medical Center, De Boelelaan 1117, 1007 MB Amsterdam, The Netherlands
| | - Yvo M. Smulders
- Department of Internal Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Etto C. Eringa
- Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
| | | | - Armand R. J. Girbes
- Department of Intensive Care, VU University Medical Center, De Boelelaan 1117, 1007 MB Amsterdam, The Netherlands
| | - Kimberley E. Wever
- SYstematic Review Centre for Laboratory animal Experimentation (SYRCLE), Department for Health Evidence, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Carlijn R. Hooijmans
- SYstematic Review Centre for Laboratory animal Experimentation (SYRCLE), Department for Health Evidence, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
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Racine ML, Crecelius AR, Luckasen GJ, Larson DG, Dinenno FA. Inhibition of Na + /K + -ATPase and K IR channels abolishes hypoxic hyperaemia in resting but not contracting skeletal muscle of humans. J Physiol 2018; 596:3371-3389. [PMID: 29603743 DOI: 10.1113/jp275913] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Accepted: 03/27/2018] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS Increasing blood flow (hyperaemia) to exercising muscle helps match oxygen delivery and metabolic demand. During exercise in hypoxia, there is a compensatory increase in muscle hyperaemia that maintains oxygen delivery and tissue oxygen consumption. Nitric oxide (NO) and prostaglandins (PGs) contribute to around half of the augmented hyperaemia during hypoxic exercise, although the contributors to the remaining response are unknown. In the present study, inhibiting NO, PGs, Na+ /K+ -ATPase and inwardly rectifying potassium (KIR ) channels did not blunt augmented hyperaemia during hypoxic exercise beyond previous observations with NO/PG block alone. Furthermore, although inhibition of only Na+ /K+ -ATPase and KIR channels abolished hyperaemia during hypoxia at rest, it had no effect on augmented hyperaemia during hypoxic exercise. This is the first study in humans to demonstrate that Na+ /K+ -ATPase and KIR channel activation is required for augmented muscle hyperaemia during hypoxia at rest but not during hypoxic exercise, thus providing new insight into vascular control. ABSTRACT Exercise hyperaemia in hypoxia is augmented relative to the same exercise intensity in normoxia. During moderate-intensity handgrip exercise, endothelium-derived nitric oxide (NO) and vasodilating prostaglandins (PGs) contribute to ∼50% of the augmented forearm blood flow (FBF) response to hypoxic exercise (HypEx), although the mechanism(s) underlying the remaining response are unclear. We hypothesized that combined inhibition of NO, PGs, Na+ /K+ -ATPase and inwardly rectifying potassium (KIR ) channels would abolish the augmented hyperaemic response in HypEx. In healthy young adults, FBF responses were measured (Doppler ultrasound) and forearm vascular conductance was calculated during 5 min of rhythmic handgrip exercise at 20% maximum voluntary contraction under regional sympathoadrenal inhibition in normoxia and isocapnic HypEx (O2 saturation ∼80%). Compared to control, combined inhibition of NO, PGs, Na+ /K+ -ATPase and KIR channels (l-NMMA + ketorolac + ouabain + BaCl2; Protocol 1; n = 10) blunted the compensatory increase in FBF during HypEx by ∼50% (29 ± 6 mL min-1 vs. 62 ± 8 mL min-1 , respectively, P < 0.05). By contrast, ouabain + BaCl2 alone (Protocol 2; n = 10) did not affect this augmented hyperaemic response (50 ± 11 mL min-1 vs. 60 ± 13 mL min-1 , respectively, P > 0.05). However, the blocked condition in both protocols abolished the hyperaemic response to hypoxia at rest (P < 0.05). We conclude that activation of Na+ /K+ -ATPase and KIR channels is involved in the hyperaemic response to hypoxia at rest, although it does not contribute to the augmented exercise hyperaemia during hypoxia in humans.
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Affiliation(s)
- Matthew L Racine
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Anne R Crecelius
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Gary J Luckasen
- Cardiovascular Research Center, Colorado State University, Fort Collins, CO, USA.,Medical Center of the Rockies Foundation, University of Colorado Health System, Loveland, CO, USA
| | - Dennis G Larson
- Medical Center of the Rockies Foundation, University of Colorado Health System, Loveland, CO, USA
| | - Frank A Dinenno
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA.,Cardiovascular Research Center, Colorado State University, Fort Collins, CO, USA
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7
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Salomonsson M, Brasen JC, Sorensen CM. Role of renal vascular potassium channels in physiology and pathophysiology. Acta Physiol (Oxf) 2017; 221:14-31. [PMID: 28371470 DOI: 10.1111/apha.12882] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/10/2016] [Accepted: 03/22/2017] [Indexed: 12/31/2022]
Abstract
The control of renal vascular tone is important for the regulation of salt and water balance, blood pressure and the protection against damaging elevated glomerular pressure. The K+ conductance is a major factor in the regulation of the membrane potential (Vm ) in vascular smooth muscle (VSMC) and endothelial cells (EC). The vascular tone is controlled by Vm via its effect on the opening probability of voltage-operated Ca2+ channels (VOCC) in VSMC. When K+ conductance increases Vm becomes more negative and vasodilation follows, while deactivation of K+ channels leads to depolarization and vasoconstriction. K+ channels in EC indirectly participate in the control of vascular tone by endothelium-derived vasodilation. Therefore, by regulating the tone of renal resistance vessels, K+ channels have a potential role in the control of fluid homoeostasis and blood pressure as well as in the protection of the renal parenchyma. The main classes of K+ channels (calcium activated (KCa ), inward rectifier (Kir ), voltage activated (Kv ) and ATP sensitive (KATP )) have been found in the renal vessels. In this review, we summarize results available in the literature and our own studies in the field. We compare the ambiguous in vitro and in vivo results. We discuss the role of single types of K+ channels and the integrated function of several classes. We also deal with the possible role of renal vascular K+ channels in the pathophysiology of hypertension, diabetes mellitus and sepsis.
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Affiliation(s)
| | - J. C. Brasen
- Department of Electrical Engineering; Technical University of Denmark; Kgs. Lyngby Denmark
| | - C. M. Sorensen
- Department of Biomedical Sciences; Division of Renal and Vascular Physiology; University of Copenhagen; Copenhagen Denmark
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8
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Hyperoxia does not directly affect vascular tone in isolated arteries from mice. PLoS One 2017; 12:e0182637. [PMID: 28796814 PMCID: PMC5552161 DOI: 10.1371/journal.pone.0182637] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 07/22/2017] [Indexed: 01/10/2023] Open
Abstract
Hospitalized patients often receive oxygen supplementation, which can lead to a supraphysiological oxygen tension (hyperoxia). Hyperoxia can have hemodynamic effects, including an increase in systemic vascular resistance. This increase suggests hyperoxia-induced vasoconstriction, yet reported direct effects of hyperoxia on vessel tone have been inconsistent. Furthermore, hyperoxia-induced changes in vessel diameter have not been studied in mice, currently the most used mammal model of disease. In this study we set out to develop a pressure-myograph model using isolated vessels from mice for investigation of pathways involved in hyperoxic vasoconstriction. Isolated conduit and resistance arteries (femoral artery and gracilis arteriole, respectively) from C57BL/6 mice were exposed to normoxia (PO2 of 80 mmHg) and three levels of hyperoxia (PO2 of 215, 375 and 665 mmHg) in a no-flow pressure myograph setup. Under the different PO2 levels, dose-response agonist induced endothelium-dependent vasodilation (acetylcholine, arachidonic acid), endothelium-independent vasodilation (s-nitroprusside), as well as vasoconstriction (norepinephrine, prostaglandin F2α) were examined. The investigated arteries did not respond to oxygen by a change in vascular tone. In the dose-response studies, maximal responses and EC50 values to any of the aforementioned agonists were not affected by hyperoxia either. We conclude that arteries and arterioles from healthy mice are not intrinsically sensitive to hyperoxic conditions. The present ex-vivo model is therefore not suitable for further research into mechanisms of hyperoxic vasoconstriction.
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9
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Dora KA. Conducted dilatation to ATP and K + in rat skeletal muscle arterioles. Acta Physiol (Oxf) 2017; 219:202-218. [PMID: 26804547 PMCID: PMC5215486 DOI: 10.1111/apha.12656] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 11/25/2015] [Accepted: 01/19/2016] [Indexed: 11/28/2022]
Abstract
AIM During exercise in humans, circulating levels of ATP and K+ increase at a time when blood flow increases to satisfy metabolic demand. Both molecules can activate arteriolar K+ channels to stimulate vasodilatation; here, it is established whether conducted dilatation is observed in a skeletal muscle bed. METHODS Isolated and cannulated rat cremaster arterioles were used to assess both local and conducted responses. Agents were either added to the bath, focally pulse-ejected to the downstream end of arterioles, or in triple-cannulated arterioles, luminally perfused into the downstream branches to assess both local and conducted responses. RESULTS The endothelium-dependent agonist ACh and the KATP channel opener levcromakalim each stimulated both local and conducted vasodilatation. Focal, bolus delivery of ATP (10 μm) or KCl (33 mm) to the outside of arterioles stimulated a biphasic vasomotor response: rapid vasoconstriction followed by dilatation as each washed away. At lower concentrations of KCl (19 mm), constriction was avoided, and instead, Ba2+ -sensitive local dilatation and conducted dilatation were both observed. Luminal perfusion of ATP avoided constriction and activated P2Y1 receptors stimulating vasodilatation secondary to opening of KCa channels. In triple-cannulated arterioles, either ATP (10 μm) or K+ (15 mm) luminally perfused into daughter branches of a bifurcation stimulated local dilatation which conducted into the parent arteriole. CONCLUSION The recognized physiological autocrine and paracrine mediators ATP and K+ each act to evoke both local and conducted vasodilatation in rat cremaster arterioles. Therefore, in situations when circulating levels are raised, such as during exercise, these agents can act as important regulators of blood flow.
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Affiliation(s)
- K. A. Dora
- Department of PharmacologyUniversity of OxfordOxfordUK
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10
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Jackson WF. Arteriolar oxygen reactivity: where is the sensor and what is the mechanism of action? J Physiol 2016; 594:5055-77. [PMID: 27324312 PMCID: PMC5023707 DOI: 10.1113/jp270192] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 06/13/2016] [Indexed: 01/02/2023] Open
Abstract
Arterioles in the peripheral microcirculation are exquisitely sensitive to changes in PO2 in their environment: increases in PO2 cause vasoconstriction while decreases in PO2 result in vasodilatation. However, the cell type that senses O2 (the O2 sensor) and the signalling pathway that couples changes in PO2 to changes in arteriolar tone (the mechanism of action) remain unclear. Many (but not all) ex vivo studies of isolated cannulated resistance arteries and large, first-order arterioles support the hypothesis that these vessels are intrinsically sensitive to PO2 with the smooth muscle, endothelial cells, or red blood cells serving as the O2 sensor. However, in situ studies testing these hypotheses in downstream arterioles have failed to find evidence of intrinsic O2 sensitivity, and instead have supported the idea that extravascular cells sense O2 . Similarly, ex vivo studies of isolated, cannulated resistance arteries and large first-order arterioles support the hypotheses that O2 -dependent inhibition of production of vasodilator cyclooxygenase products or O2 -dependent destruction of nitric oxide mediates O2 reactivity of these upstream vessels. In contrast, most in vivo studies of downstream arterioles have disproved these hypotheses and instead have provided evidence supporting the idea that O2 -dependent production of vasoconstrictors mediates arteriolar O2 reactivity, with significant regional heterogeneity in the specific vasoconstrictor involved. Oxygen-induced vasoconstriction may serve as a protective mechanism to reduce the oxidative burden to which a tissue is exposed, a process that is superimposed on top of the local mechanisms which regulate tissue blood flow to meet a tissue's metabolic demand.
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Affiliation(s)
- William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, 48824, USA.
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11
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Abstract
Nitric oxide (NO) generated by endothelial cells to relax vascular smooth muscle is one of the most intensely studied molecules in the past 25 years. Much of what is known about NO regulation of NO is based on blockade of its generation and analysis of changes in vascular regulation. This approach has been useful to demonstrate the importance of NO in large scale forms of regulation but provides less information on the nuances of NO regulation. However, there is a growing body of studies on multiple types of in vivo measurement of NO in normal and pathological conditions. This discussion will focus on in vivo studies and how they are reshaping the understanding of NO's role in vascular resistance regulation and the pathologies of hypertension and diabetes mellitus. The role of microelectrode measurements in the measurement of [NO] will be considered because much of the controversy about what NO does and at what concentration depends upon the measurement methodology. For those studies where the technology has been tested and found to be well founded, the concept evolving is that the stresses imposed on the vasculature in the form of flow-mediated stimulation, chemicals within the tissue, and oxygen tension can cause rapid and large changes in the NO concentration to affect vascular regulation. All these functions are compromised in both animal and human forms of hypertension and diabetes mellitus due to altered regulation of endothelial cells and formation of oxidants that both damage endothelial cells and change the regulation of endothelial nitric oxide synthase.
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Affiliation(s)
- Harold Glenn Bohlen
- Department of Cellular and Integrative Physiology, Indiana University Medical School, Indianapolis, Indiana, Indiana, USA
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12
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Kibel A, Novak S, Cosic A, Mihaljevic Z, Falck JR, Drenjancevic I. Hyperbaric oxygenation modulates vascular reactivity to angiotensin-(1-7) in diabetic rats: potential role of epoxyeicosatrienoic acids. Diab Vasc Dis Res 2015; 12:33-45. [PMID: 25326234 DOI: 10.1177/1479164114553424] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Previously, a facilitating effect of hyperbaric oxygenation (HBO₂) on aortic ring responses to angiotensin-(1-7) in healthy rats was reported, with epoxyeicosatrienoic acids (EETs) possibly playing an important role. The aim of this study was to assess whether HBO₂ exerts similar effects in diabetic rats and to further explore the role of specific cytochrome P450 (CYP) enzymes in changes induced by HBO₂. Aortic relaxation to angiotensin-(1-7) was significantly higher in HBO₂ diabetic rats compared to control diabetic rats, while HBO₂ had no effect on angiotensin II contraction. N-methylsulphonyl-6-(2-propargyloxyphenyl/hexanamide inhibited the facilitation of angiotensin-(1-7) responses in HBO₂ rats, suggesting an important role of EETs in this modulation. mRNA expression of CYP2J3 and protein expression of CYP2C11 were significantly upregulated in HBO₂ diabetic rats, whereas CYP4A1, CYP4A2 and CYP4A3 mRNA and CYP2J3 protein expression was similar between groups. Mean arterial pressure, ferric reducing ability of plasma and Thiobarbituric Acid Reactive Substances levels and serum angiotensin-(1-7) concentrations were not significantly changed.
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MESH Headings
- 8,11,14-Eicosatrienoic Acid/analogs & derivatives
- 8,11,14-Eicosatrienoic Acid/metabolism
- Amides/pharmacology
- Angiotensin I/blood
- Angiotensin I/pharmacology
- Angiotensin II/pharmacology
- Animals
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/metabolism
- Aorta, Thoracic/physiopathology
- Aryl Hydrocarbon Hydroxylases/antagonists & inhibitors
- Aryl Hydrocarbon Hydroxylases/genetics
- Aryl Hydrocarbon Hydroxylases/metabolism
- Cytochrome P-450 Enzyme System/chemistry
- Cytochrome P-450 Enzyme System/genetics
- Cytochrome P-450 Enzyme System/metabolism
- Cytochrome P450 Family 2
- Diabetes Mellitus, Type 1/complications
- Diabetes Mellitus, Type 1/metabolism
- Diabetes Mellitus, Type 1/physiopathology
- Diabetes Mellitus, Type 1/therapy
- Diabetic Angiopathies/prevention & control
- Enzyme Induction
- Enzyme Inhibitors/pharmacology
- Hyperbaric Oxygenation/adverse effects
- Male
- Oxidative Stress
- Peptide Fragments/blood
- Peptide Fragments/pharmacology
- Rats, Sprague-Dawley
- Steroid 16-alpha-Hydroxylase/antagonists & inhibitors
- Steroid 16-alpha-Hydroxylase/genetics
- Steroid 16-alpha-Hydroxylase/metabolism
- Vascular Resistance/drug effects
- Vasoconstriction/drug effects
- Vasodilation/drug effects
- Vasodilator Agents/blood
- Vasodilator Agents/pharmacology
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Affiliation(s)
| | - Sanja Novak
- Faculty of Medicine, University of Osijek, Osijek, Croatia
| | - Anita Cosic
- Faculty of Medicine, University of Osijek, Osijek, Croatia
| | | | - John R Falck
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA
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13
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Reglin B, Pries AR. Metabolic control of microvascular networks: oxygen sensing and beyond. J Vasc Res 2014; 51:376-92. [PMID: 25531863 DOI: 10.1159/000369460] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 10/04/2014] [Indexed: 11/19/2022] Open
Abstract
The metabolic regulation of blood flow is central to guaranteeing an adequate supply of blood to the tissues and microvascular network stability. It is assumed that vascular reactions to local oxygenation match blood supply to tissue demand via negative-feedback regulation. Low oxygen (O2) levels evoke vasodilatation, and thus an increase of blood flow and oxygen supply, by increasing (decreasing) the release of vasodilatory (vasoconstricting) metabolic signal substances with decreasing partial pressure of O2. This review analyses the principles of metabolic vascular control with a focus on the prevailing feedback regulations. We propose the following hypotheses with respect to vessel diameter adaptation. (1) In addition to O2-dependent signaling, metabolic vascular regulation can be effected by signal substances produced independently of local oxygenation (reflecting the presence of cells) due to the dilution effect. (2) Control of resting vessel tone, and thus perfusion reserve, could be explained by a vascular activity/hypoxia memory. (3) Vasodilator but not vasoconstrictor signaling can prevent shunt perfusion via signal conduction upstream to feeding arterioles. (4) For low perfusion heterogeneity in the steady state, metabolic signaling from the vessel wall or a perivascular tissue sleeve is optimal. (5) For amplification of perfusion during transient increases of tissue demand, red blood cell-derived vasodilators or vasoconstrictors diluted in flowing blood may be relevant.
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Roy TK, Secomb TW. Functional sympatholysis and sympathetic escape in a theoretical model for blood flow regulation. Front Physiol 2014; 5:192. [PMID: 24904428 PMCID: PMC4033268 DOI: 10.3389/fphys.2014.00192] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 05/05/2014] [Indexed: 11/13/2022] Open
Abstract
A mathematical simulation of flow regulation in vascular networks is used to investigate the interaction between arteriolar vasoconstriction due to sympathetic nerve activity (SNA) and vasodilation due to increased oxygen demand. A network with 13 vessel segments in series is used, each segment representing a different size range of arterioles or venules. The network includes five actively regulating arteriolar segments with time-dependent diameters influenced by shear stress, wall tension, metabolic regulation, and SNA. Metabolic signals are assumed to be propagated upstream along vessel walls via a conducted response. The model exhibits functional sympatholysis, in which sympathetic vasoconstriction is partially abrogated by increases in metabolic demand, and sympathetic escape, in which SNA elicits an initial vasoconstriction followed by vasodilation. In accordance with experimental observations, these phenomena are more prominent in small arterioles than in larger arterioles when SNA is assumed to act equally on arterioles of all sizes. The results imply that a mechanism based on the competing effects on arteriolar tone of SNA and conducted metabolic signals can account for several observed characteristics of functional sympatholysis, including the different responses of large and small arterioles.
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Affiliation(s)
- Tuhin K Roy
- Department of Anesthesiology, Mayo Clinic Rochester, MN, USA
| | - Timothy W Secomb
- Department of Physiology, Arizona Health Sciences Center, University of Arizona Tucson, AZ, USA
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Drenjancevic I, Kibel A. Restoring Vascular Function with Hyperbaric Oxygen Treatment: Recovery Mechanisms. J Vasc Res 2013; 51:1-13. [DOI: 10.1159/000355925] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 09/05/2013] [Indexed: 11/19/2022] Open
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Fry BC, Roy TK, Secomb TW. Capillary recruitment in a theoretical model for blood flow regulation in heterogeneous microvessel networks. Physiol Rep 2013; 1:e00050. [PMID: 24040516 PMCID: PMC3770315 DOI: 10.1002/phy2.50] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
In striated muscle, the number of capillaries containing moving red blood cells increases with increasing metabolic demand. This phenomenon, termed capillary recruitment, has long been recognized, but its mechanism has been unclear. Here, a theoretical model for metabolic blood flow regulation in a heterogeneous network is used to test the hypothesis that capillary recruitment occurs as a result of active control of arteriolar diameters, combined with unequal partition of hematocrit at diverging microvascular bifurcations. The network structure is derived from published observations of hamster cremaster muscle in control and dilated states. The model for modulation of arteriolar diameters includes length-tension characteristics of vascular smooth muscle and responses of smooth muscle tone to myogenic, shear-dependent, and metabolic stimuli. Blood flow is simulated including nonuniform hematocrit distribution. Convective and diffusive oxygen transport in the network is simulated. Oxygen-dependent metabolic signals are assumed to be conducted upstream from distal vessels to arterioles. With increasing oxygen demand, arterioles dilate, blood flow increases, and the numbers of flowing arterioles and capillaries, as defined by red blood cell flux above a small threshold value, increase. Unequal hematocrit partition at diverging bifurcations contributes to recruitment and enhances tissue oxygenation. The results imply that capillary recruitment, as observed in the hamster cremaster preparations, can occur as a consequence of local control of arteriolar tone and the resulting nonuniform changes in red blood cell fluxes, and provide an explanation for observations of sequential recruitment of individual capillaries in response to modulation of terminal arteriolar diameter.
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Affiliation(s)
- Brendan C Fry
- Program in Applied Mathematics, University of Arizona, Tucson AZ 85721
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Ngo AT, Riemann M, Holstein-Rathlou NH, Torp-Pedersen C, Jensen LJ. Significance of K(ATP) channels, L-type Ca²⁺ channels and CYP450-4A enzymes in oxygen sensing in mouse cremaster muscle arterioles in vivo. BMC PHYSIOLOGY 2013; 13:8. [PMID: 23663730 PMCID: PMC3663688 DOI: 10.1186/1472-6793-13-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 05/08/2013] [Indexed: 12/20/2022]
Abstract
Background ATP-sensitive K+ channels (KATP channels), NO, prostaglandins, 20-HETE and L-type Ca2+ channels have all been suggested to be involved in oxygen sensing in skeletal muscle arterioles, but the role of the individual mechanisms remain controversial. We aimed to establish the importance of these mechanisms for oxygen sensing in arterioles in an in vivo model of metabolically active skeletal muscle. For this purpose we utilized the exteriorized cremaster muscle of anesthetized mice, in which the cremaster muscle was exposed to controlled perturbation of tissue PO2. Results Change from “high” oxygen tension (PO2 = 153.4 ± 3.4 mmHg) to “low” oxygen tension (PO2 = 13.8 ± 1.3 mmHg) dilated cremaster muscle arterioles from 11.0 ± 0.4 μm to 32.9 ± 0.9 μm (n = 28, P < 0.05). Glibenclamide (KATP channel blocker) caused maximal vasoconstriction, and abolished the dilation to low oxygen, whereas the KATP channel opener cromakalim caused maximal dilation and prevented the constriction to high oxygen. When adding cromakalim on top of glibenclamide or vice versa, the reactivity to oxygen was gradually restored. Inhibition of L-type Ca2+ channels using 3 μM nifedipine did not fully block basal tone in the arterioles, but rendered them unresponsive to changes in PO2. Inhibition of the CYP450-4A enzyme using DDMS blocked vasoconstriction to an increase in PO2, but had no effect on dilation to low PO2. Conclusions We conclude that: 1) L-type Ca2+ channels are central to oxygen sensing, 2) KATP channels are permissive for the arteriolar response to oxygen, but are not directly involved in the oxygen sensing mechanism and 3) CYP450-4A mediated 20-HETE production is involved in vasoconstriction to high PO2.
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Affiliation(s)
- Anh Thuc Ngo
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, The Panum institute, University of Copenhagen, Blegdamsvej 3, Copenhagen N, DK-2200, Denmark.
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Han JA, Seo EY, Kim HJ, Park SJ, Yoo HY, Kim JY, Shin DM, Kim JK, Zhang YH, Kim SJ. Hypoxia-augmented constriction of deep femoral artery mediated by inhibition of eNOS in smooth muscle. Am J Physiol Cell Physiol 2013; 304:C78-88. [DOI: 10.1152/ajpcell.00176.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
In contrast to the conventional belief that systemic arteries dilate under hypoxia, we found that α-adrenergic contraction of rat deep femoral artery (DFA) is largely augmented by hypoxia (HVCDFA) while hypoxia (3% Po2) alone had no effect. HVCDFA was consistently observed in both endothelium-intact and -denuded vessels with partial pretone by phenylephrine (PhE) or by other conditions (e.g., K+ channel blocker). Patch-clamp study showed no change in the membrane conductance of DFA myocytes by hypoxia. The RhoA-kinase inhibitor Y27632 attenuated HVCDFA. The nitric oxide synthase inhibitor [nitro-l-arginine methyl ester (l-NAME)] and soluble guanylate cyclase inhibitor [oxadiazole quinoxalin (ODQ)] strongly augmented the PhE-pretone, while neither of the agents had effect without pretone. NADPH oxidase type 4 (NOX4) inhibitors (diphenylene iodonium and plumbagin) also potentiated PhE-pretone, which was reversed by NO donor. No additive HVCDFA was observed under the pretreatment with l-NAME, ODQ, or plumbagin. Western blot and immunohistochemistry analysis showed that both NOX4 and endothelial nitric oxide synthase (eNOS) are expressed in smooth muscle layer of DFA. Various mitochondria inhibitors (rotenone, myxothiazol, and cyanide) prevented HVCDFA. From the pharmacological data, as a mechanism for HVCDFA, we suggest hypoxic inhibition of eNOS in myocytes. The putative role of NOX4 and mitochondria requires further investigation. The HVCDFA may prevent imbalance between cardiac output and skeletal blood flow under emergent hypoxia combined with increased sympathetic tone.
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Affiliation(s)
- Jung-A. Han
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea
- Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Eun Yeoung Seo
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea
- Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Hae Jin Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea
| | - Su Jung Park
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea
| | - Hae Young Yoo
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea
| | - Jin Young Kim
- Department of Anesthesiology-Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Suwon, Korea; and
| | - Dong Min Shin
- Department of Oral Biology, Yonsei University College of Dentistry, Seoul, Korea
| | - Jin Kyoung Kim
- Department of Anesthesiology-Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Suwon, Korea; and
| | - Yin Hua Zhang
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea
| | - Sung Joon Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea
- Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
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Kapela A, Nagaraja S, Parikh J, Tsoukias NM. Modeling Ca2+ signaling in the microcirculation: intercellular communication and vasoreactivity. Crit Rev Biomed Eng 2012; 39:435-60. [PMID: 22196162 DOI: 10.1615/critrevbiomedeng.v39.i5.50] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A network of intracellular signaling pathways and complex intercellular interactions regulate calcium mobilization in vascular cells, arteriolar tone, and blood flow. Different endothelium-derived vasoreactive factors have been identified and the importance of myoendothelial communication in vasoreactivity is now well appreciated. The ability of many vascular networks to conduct signals upstream also is established. This phenomenon is critical for both short-term changes in blood perfusion as well as long-term adaptations of a vascular network. In addition, in a phenomenon termed vasomotion, arterioles often exhibit spontaneous oscillations in diameter. This is thought to improve tissue oxygenation and enhance blood flow. Experimentation has begun to reveal important aspects of the regulatory machinery and the significance of these phenomena for the regulation of local perfusion and oxygenation. Mathematical modeling can assist in elucidating the complex signaling mechanisms that participate in these phenomena. This review highlights some of the important experimental studies and relevant mathematical models that provide the current understanding of these mechanisms in vasoreactivity.
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Affiliation(s)
- Adam Kapela
- Department of Biomedical Engineering, Florida International University, Miami, FL, USA
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20
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Abstract
Several apparent paradoxes are evident when one compares mathematical predictions from models of nitric oxide (NO) diffusion and convection in vasculature structures with experimental measurements of NO (or related metabolites) in animal and human studies. Values for NO predicted from mathematical models are generally much lower than in vivo NO values reported in the literature for experiments, specifically with NO microelectrodes positioned at perivascular locations next to different sizes of blood vessels in the microcirculation and NO electrodes inserted into a wide range of tissues supplied by the microcirculation of each specific organ system under investigation. There continues to be uncertainty about the roles of NO scavenging by hemoglobin versus a storage function that may conserve NO, and other signaling targets for NO need to be considered. This review describes model predictions and relevant experimental data with respect to several signaling pathways in the microcirculation that involve NO.
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Roy TK, Pries AR, Secomb TW. Theoretical comparison of wall-derived and erythrocyte-derived mechanisms for metabolic flow regulation in heterogeneous microvascular networks. Am J Physiol Heart Circ Physiol 2012; 302:H1945-52. [PMID: 22408023 DOI: 10.1152/ajpheart.01176.2011] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objective of this study is to compare the effectiveness of metabolic signals derived from erythrocytes and derived from the vessel wall for regulating blood flow in heterogeneous microvascular networks. A theoretical model is used to simulate blood flow, mass transport, and vascular responses. The model accounts for myogenic, shear-dependent, and metabolic flow regulation. Metabolic signals are assumed to be propagated upstream along vessel walls via a conducted response. Arteriolar tone is assumed to depend on the conducted metabolic signal as well as local wall shear stress and wall tension, and arteriolar diameters are calculated based on vascular smooth muscle mechanics. The model shows that under certain conditions metabolic regulation based on wall-derived signals can be more effective in matching perfusion to local oxygen demand relative to regulation based on erythrocyte-derived signals, resulting in higher extraction and lower oxygen deficit. The lower effectiveness of the erythrocyte-derived signal is shown to result in part from the unequal partition of hematocrit at diverging bifurcations, such that low-flow vessels tend to receive a reduced hematocrit and thereby experience a reduced erythrocyte-derived metabolic signal. The model simulations predict that metabolic signals independent of erythrocytes may play an important role in local metabolic regulation of vascular tone and flow distribution in heterogeneous microvessel networks.
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Affiliation(s)
- Tuhin K Roy
- Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
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Sorensen CM, Braunstein TH, Holstein-Rathlou NH, Salomonsson M. Role of vascular potassium channels in the regulation of renal hemodynamics. Am J Physiol Renal Physiol 2012; 302:F505-18. [DOI: 10.1152/ajprenal.00052.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
K+ conductance is a major determinant of membrane potential ( Vm) in vascular smooth muscle (VSMC) and endothelial cells (EC). The vascular tone is controlled by Vm through the action of voltage-operated Ca2+ channels (VOCC) in VSMC. Increased K+ conductance leads to hyperpolarization and vasodilation, while inactivation of K+ channels causes depolarization and vasoconstriction. K+ channels in EC indirectly participate in the control of vascular tone by several mechanisms, e.g., release of nitric oxide and endothelium-derived hyperpolarizing factor. In the kidney, a change in the activity of one or more classes of K+ channels will lead to a change in hemodynamic resistance and therefore of renal blood flow and glomerular filtration pressure. Through these effects, the activity of renal vascular K+ channels influences renal salt and water excretion, fluid homeostasis, and ultimately blood pressure. Four main classes of K+ channels [calcium activated (KCa), inward rectifier (Kir), voltage activated (KV), and ATP sensitive (KATP)] are found in the renal vasculature. Several in vitro experiments have suggested a role for individual classes of K+ channels in the regulation of renal vascular function. Results from in vivo experiments are sparse. We discuss the role of the different classes of renal vascular K+ channels and their possible role in the integrated function of the renal microvasculature. Since several pathological conditions, among them hypertension, are associated with alterations in K+ channel function, the role of renal vascular K+ channels in the control of salt and water excretion deserves attention.
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Affiliation(s)
- Charlotte Mehlin Sorensen
- Institute of Biomedical Sciences, Division of Renal and Vascuar Physiology, The Panum Institute, and
| | - Thomas Hartig Braunstein
- Danish National Research Foundation Center for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | | | - Max Salomonsson
- Institute of Biomedical Sciences, Division of Renal and Vascuar Physiology, The Panum Institute, and
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Wan J, Forsyth AM, Stone HA. Red blood cell dynamics: from cell deformation to ATP release. Integr Biol (Camb) 2011; 3:972-81. [PMID: 21935538 DOI: 10.1039/c1ib00044f] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The mechanisms of red blood cell (RBC) deformation under both static and dynamic, i.e., flow, conditions have been studied extensively since the mid 1960s. Deformation-induced biochemical reactions and possible signaling in RBCs, however, were proposed only fifteen years ago. Therefore, the fundamental relationship between RBC deformation and cellular signaling dynamics i.e., mechanotransduction, remains incompletely understood. Quantitative understanding of the mechanotransductive pathways in RBCs requires integrative studies of physical models of RBC deformation and cellular biochemical reactions. In this article we review the physical models of RBC deformation, spanning from continuum membrane mechanics to cellular skeleton dynamics under both static and flow conditions, and elaborate the mechanistic links involved in deformation-induced ATP release.
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Affiliation(s)
- Jiandi Wan
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA
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Arciero JC, Secomb TW. Spontaneous oscillations in a model for active control of microvessel diameters. MATHEMATICAL MEDICINE AND BIOLOGY-A JOURNAL OF THE IMA 2011; 29:163-80. [PMID: 21525236 DOI: 10.1093/imammb/dqr005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A new theory is presented for the origin of spontaneous oscillations in blood vessel diameters that are observed experimentally in the microcirculation. These oscillations, known as vasomotion, involve timevarying contractions of the vascular smooth muscle in the walls of arterioles. It is shown that such oscillations can arise as a result of interactions between the mechanics of the vessel wall and the dynamics of the active contraction of smooth muscle cells in response to circumferential tension in the wall. A theoretical model is developed in which the diameter and the degree of activation in a vessel are dynamic variables. The model includes effects of wall shear stress and oxygen-dependent metabolic signals on smooth muscle activation and is applied to a single vessel and to simplified network structures. The model equations predict limit cycle oscillations for certain ranges of parameters such as wall shear stress, arterial pressure and oxygen consumption rate. Predicted characteristics of the oscillations, including their sensitivity to arterial pressure, are consistent with experimental observations.
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Affiliation(s)
- J C Arciero
- Department of Mathematics, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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