Reconsidering the Effect of Local Plasma Convection in a Classical Model of Oxygen Transport in Capillaries

Bos, Cees; Hoofd, Louis; Oostendorp, Thom F.

doi:10.1006/mvre.1996.0005

Cited by 13 publications

(6 citation statements)

References 24 publications

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“…Using the values D NO ϭ 3.3 ϫ 10 Ϫ5 cm 2 /s (2) and r ϭ 2.44 ϫ 10 Ϫ4 cm (20), we arrive at a value for k NO /N of 1.01 ϫ 10 Ϫ7 s Ϫ1 , which compares favorably to our experimental value (0.774 ϫ 10 Ϫ7 s Ϫ1 ). Hakim et al (23) reported that the half-life of NO in the presence of oxyHb (1.55 M) is 11.5 s. They used a probe similar to the Clark-type sensor for oxygen.…”

Section: Discussionsupporting

confidence: 67%

Diffusion-limited Reaction of Free Nitric Oxide with Erythrocytes

Liu

Miller

Joshi

et al. 1998

Journal of Biological Chemistry

473

398

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Nitric oxide (NO) 1 is one of the 10 smallest, stable molecules of the hundreds of millions in nature (1). According to Stokes' Law, the diffusibility of a molecule in the condensed phase is inversely proportional to its molecular radius, which thus makes NO one of the most rapidly diffusible molecules known. Its diffusion constant (D) is approximately 3300 -3800 m 2 /s, whether measured in aqueous solution (2) or in intact tissue (e.g. brain (3)). Membranes and other hydrophobic structures in tissue are no barrier to diffusion of NO because of its solubility in hydrophobic phases (4).The reaction of free NO with oxyhemoglobin is rapid (bimolecular rate constant k ϭ 3.4 ϫ 10 7 M Ϫ1 s Ϫ1 (5)), and from this rate constant it can be calculated that the half-life of NO in the presence of a concentration of hemoglobin equivalent to that in the bloodstream (15 g/dl) would be very short, approximately 2 ϫ 10 Ϫ6 s. As we have pointed out previously (6, 7), the extremely rapid diffusibility of NO coupled with its rapid reaction with oxyhemoglobin apparently poses a difficulty in the postulate that free NO is the endothelium-derived relaxing factor.Using an electrochemical method, we describe here the results of measurements of the disappearance of NO upon reaction with either oxyhemoglobin in solution or oxyhemoglobin when contained within intact erythrocytes. We find that, as reported in 1927 for the reaction of O 2 with deoxyhemoglobin (8), the NO reaction with intact RBCs is considerably slower than with an equivalent concentration of free oxyhemoglobin. We present a mathematical analysis of this phenomenon, which demonstrates that the rate of the reaction of NO with intraerythrocytic hemoglobin is limited by the rate of diffusion of NO into the cell. From our data, we estimate that in whole blood the half-life of NO will be less than 2 ms, which, although quite rapid, is considerably longer than in the presence of free hemoglobin. EXPERIMENTAL PROCEDURESPreparation of NO Solution-6 ml of phosphate-buffered saline (PBS: 15 mM phosphate (potassium) plus 0.09% NaCl pH 7.4) in a plastic vial was used in preparing saturated NO solution. The solution was bubbled with argon gas (Aldrich) for 30 min and then changed to NO gas (Aldrich) for 20 min. The NO gas was passed first through a gaswashing bottle containing 1 M deaerated KOH solution.RBC and Free Hemoglobin Preparation-Blood was withdrawn from rats and centrifuged at 2300 ϫ g for 10 min. The plasma and buffy coat were discarded, and the RBC pellet was washed 3 times with PBS (pH 7.4). The packed RBCs then were added to PBS and the solution was stirred gently. Cells were counted with a hemocytometer and were stored on ice for use. To prepare free oxyHb, 2 ml of counted RBCs was centrifuged at 2300 g for 10 min (4°C). The packed RBCs were then added to 40 ml of 5 mM phosphate solution (pH 8), stirred and allowed to incubate for 30 min for hemolysis.Electrochemical Measurements-All electrochemical measurements were carried out at 25 Ϯ 2°C by a BAS 100B electrochemical a...

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Section: Discussionsupporting

confidence: 67%

Diffusion-limited Reaction of Free Nitric Oxide with Erythrocytes

Liu

Miller

Joshi

et al. 1998

Journal of Biological Chemistry

473

398

View full text Add to dashboard Cite

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“…They found an increase in the gas exchange for the physiological blood capillary speed of 4 mm/s, hinting on the importance of blood flow for capillary gas exchange. Bos et al [4] also considered the effect of plasma flow in muscle capillaries. However, they argued that the conclusion by [3] was due to their choice of flat (constant) gas concentration profiles along the boundaries of the domain.…”

Section: Introductionmentioning

confidence: 98%

The role of red cell movement on alveolar gas diffusion

Merrikh

Lage

2005

Mat.-wiss. u. Werkstofftech.

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Existing controversy on the effect of blood flow, and more specifically red blood cell (RBC) movement, on the alveolar gas diffusion is considered. Contrary to fundamental understanding of flow (convection) effects, there seems to be a consensus in the negligible role blood flow plays on alveolar gas transport. Notwithstanding, experimental evidence indicates an increase in the efficiency of alveolar gas exchange under high cardiac output (exercising), which could be easily explained as a result of increased blood flow. A theoretical analysis of a simplified capillary blood flow configuration, with blood considered as a homogeneous fluid (no RBCs), is presented to demonstrate the strong blood (plasma) flow effect. The analysis is followed by the realistic modeling and numerical simulations of alveolar gas diffusion in a straight capillary under blood flow, with RBCs represented as discrete circles. Results indicate a substantial increase in the gas diffusion efficiency with blood speed, especially under low hematocrit and high blood speed.

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“…For a more detailed review of the theory of oxygen transport to tissues, see the review of Popel (1989) (9). The validity of these assumptions has been discussed previously by several authors (2, 5, 7–9, 19–25)…”

Section: Introductionmentioning

confidence: 71%

Numerical Simulation of Oxygen Delivery to Muscle Tissue in the Presence of Hemoglobin-Based Oxygen Carriers

Patton

Palmer

2006

Biotechnol. Prog.

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This work represents a culmination of research on oxygen transport to muscle tissue, which takes into account oxygen transport due to convection, diffusion, and the kinetics of simultaneous reactions between oxygen and hemoglobin and myoglobin. The effect of adding hemoglobin-based oxygen carriers (HBOCs) to the plasma layer of blood in a single capillary surrounded by muscle tissue based on the geometry of the Krogh tissue cylinder is examined for a range of HBOC oxygen affinity, HBOC concentration, capillary inlet oxygen tension (pO(2)), and hematocrit. The full capillary length of the hamster retractor muscle was modeled under resting (V(max) = 1.57 x 10(-4) mLO(2) mL(-1) s(-1), cell velocity (v(c)) = 0.015 cm/s) and working (V(max) = 1.57 x 10(-3) mLO(2) mL(-1) s(-1), v(c) = 0.075 cm/s) conditions. Two spacings between the red blood cell (RBC) and the capillary wall were examined, corresponding to a capillary with and without an endothelial surface layer. Simulations led to the following conclusions, which lend physiological insight into oxygen transport to muscle tissue in the presence of HBOCs: (1) The reaction kinetics between oxygen and myoglobin in the tissue region, oxygen and HBOCs in the plasma, and oxygen and RBCs in the capillary lumen should not be neglected. (2) Simulation results yielded new insight into possible mechanisms of oxygen transport in the presence of HBOCs. (3) HBOCs may act as a source or sink for oxygen in the capillary and may compete with RBCs for oxygen. (4) HBOCs return oxygen delivery to muscle tissue to normal for varying degrees of hypoxia (inlet capillary pO(2) < 30 mmHg) and anemia (hematocrit < 46%) for the hamster model.

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Reconsidering the Effect of Local Plasma Convection in a Classical Model of Oxygen Transport in Capillaries

Cited by 13 publications

References 24 publications

Diffusion-limited Reaction of Free Nitric Oxide with Erythrocytes

Diffusion-limited Reaction of Free Nitric Oxide with Erythrocytes

The role of red cell movement on alveolar gas diffusion

Numerical Simulation of Oxygen Delivery to Muscle Tissue in the Presence of Hemoglobin-Based Oxygen Carriers

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