A Theoretical Model for the Myogenic Response Based on the Length–Tension Characteristics of Vascular Smooth Muscle

Carlson, Brian E.; Secomb, Timothy W.

doi:10.1080/10739680590934745

Cited by 79 publications

(94 citation statements)

References 49 publications

(172 reference statements)

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“…2). The exponential model presented as Equation 1 was only used for comparison to the established model for arterioles developed by Carlson et al 12 ( Supplementary Fig. S1; supplementary data are available online at www .liebertonline.com/lrb).…”

Section: Resultsmentioning

confidence: 99%

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Passive Pressure–Diameter Relationship and Structural Composition of Rat Mesenteric Lymphangions

Rahbar

Weimer

Gibbs

et al. 2012

Lymphatic Research and Biology

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Background: Lymph flow depends on both the rate of lymph production by tissues and the extent of passive and active pumping. Here we aim to characterize the passive mechanical properties of a lymphangion in both midlymphangion and valve segments to assess regional differences along a lymphangion, as well as evaluating its structural composition. Methods and Results: Mesenteric lymphatic vessels were isolated and cannulated in a microchamber for pressure-diameter (P-D) testing. Vessels were inflated from 0 to 20 cmH 2 O at a rate of 4 cmH 2 O/min, and vessel diameter was continuously tracked, using an inverted microscope, video camera, and custom LabVIEW program, at both mid-lymphangion and valve segments. Isolated lymphatic vessels were also pressure-fixed at 2 and 7 cmH 2 O and imaged using a nonlinear optical microscope (NLOM) to obtain collagen and elastin structural information. We observed a highly nonlinear P-D response at low pressures (3-5 cmH 2 O), which was modeled using a three-parameter constitutive equation. No significant difference in the passive P-D response was observed between mid-lymphangion and valve regions. NLOM imaging revealed an inner elastin layer and outer collagen layer at all locations. Lymphatic valve leaflets were predominantly elastin with thick axially oriented collagen bands at the insertion points. Conclusions: We observed a highly nonlinear P-D response at low pressures (3-5 cmH 2 O) and developed the first constitutive equation to describe the passive P-D response for a lymphangion. The passive P-D response did not vary among regions, in agreement with the composition of elastin and collagen in the lymphatic wall.

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Section: Resultsmentioning

confidence: 99%

“…Numerous models have been developed for arterial microcirculatory networks and the roles of myogenic, shear, and metabolic responses in the autoregulation of blood flow. [12][13][14] However, none of these models have been adapted to describe the regulation of lymph flow.…”

Section: Introductionmentioning

confidence: 99%

Passive Pressure–Diameter Relationship and Structural Composition of Rat Mesenteric Lymphangions

Rahbar

Weimer

Gibbs

et al. 2012

Lymphatic Research and Biology

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“…The rationale for representing myogenic activation as a function of tension rather than stress was discussed by Carlson & Secomb (2005). The second term gives the shear-dependent response, where τ is the wall shear stress resulting from blood flow.…”

Section: Model Formulationmentioning

confidence: 99%

“…As defined in Carlson & Secomb (2005) and Carlson et al (2008), the passive tension is assumed to be an exponential function of diameter since tension increases rapidly with increasing circumferential stretch. D 0 is the passive diameter of the vessel at an intraluminal pressure of 100 mmHg (13.33 kPa), C pass is the passive tension at D 0 and C pass determines the steepness of the curve and was fit to experimental data.…”

Section: Model Formulationmentioning

confidence: 99%

“…The theoretical model is based on a description of the length-tension characteristics of vessel walls containing VSM Carlson et al, 2008;Carlson & Secomb, 2005). Tension, T total , generated in the wall is represented as the sum of a passive component, T pass , and an active component, expressed as the product of the maximal active tension generated by the VSM cells, T max act , and the degree of VSM activation or tone, A:…”

Section: Model Formulationmentioning

confidence: 99%

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Spontaneous oscillations in a model for active control of microvessel diameters

Arciero

Secomb²

2011

Mathematical Medicine and Biology

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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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Capillary recruitment in a theoretical model for blood flow regulation in heterogeneous microvessel networks

2013

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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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A Theoretical Model for the Myogenic Response Based on the Length–Tension Characteristics of Vascular Smooth Muscle

Abstract: The results support the hypothesis that circumferential tension or stress in the wall provides the signal for myogenic responses. The model provides a basis for simulating steady-state myogenic responses in vascular networks containing a range of vessel diameters.

Cited by 79 publications

References 49 publications

Passive Pressure–Diameter Relationship and Structural Composition of Rat Mesenteric Lymphangions

Passive Pressure–Diameter Relationship and Structural Composition of Rat Mesenteric Lymphangions

Spontaneous oscillations in a model for active control of microvessel diameters

Capillary recruitment in a theoretical model for blood flow regulation in heterogeneous microvessel networks

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