Reduction of anoxia through myoglobin-facilitated diffusion of oxygen

Salathé, Eric P.; Kolkka, Robert W.

doi:10.1016/s0006-3495(86)83529-9

Cited by 13 publications

(10 citation statements)

References 21 publications

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“…The physiological importance of facilitated transport of oxygen by myoglobin should depend on a complex interaction between oxygen delivery from capillaries to muscle cells, the myoplasmic oxygen concentration, the rate of oxygen metabolism, and various other parameters including the intracellular diffusion constants of oxygen and myoglobin. Mathematical modelling studies considering various aspects of this problem, including those of Murray (1974), Taylor & Murray (1977), Fletcher (1980), Federspiel (1986), Salathe & Kolka (1986) and Loiselle (1987), have served to theoretically quantify the possible importance of facilitated oxygen transport by myoglobin under assumed, in vivo conditions. Of the various assumptions required in these models, one of the most critical and least certain has been the value chosen for myoglobin's diffusion constant in myoplasm (denoted DMgb).…”

Section: Introductionmentioning

confidence: 99%

Measurement of myoglobin diffusivity in the myoplasm of frog skeletal muscle fibres.

Baylor

Pape

1988

The Journal of Physiology

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SUMMARY1. Experiments were carried out on intact, single skeletal muscle fibres from frog in order to estimate the apparent diffusion constant of myoglobin (denoted DAPP) in the myoplasm of living muscle cells. An optical technique was employed to measure myoglobin concentration along the fibre axis following injection of metmyoglobin (denoted metMb) at a point source. The concentration profiles were fitted by the onedimensional diffusion equation to give estimates of DAPP. The method relied on the fact that myoglobin is normally absent from these frog fibres, thus permitting resolution of the myoglobin-related absorbance above the intrinsic absorbance of the fibre.2. One complication in the method was that metMb became significantly reduced to oxymyoglobin (denoted MbO2) during the elapsed time before measurement of the concentration profile. The rate of reduction was evaluated by fitting myoglobinrelated absorbance spectra, measured at different times following injection of metMb, with in vitro absorbance spectra of metMb and MbO2. Results from four experiments indicated that reduction could be described by a first-order, irreversible reaction having an average rate constant of 0-0164 min-' (22°C). The effect of reduction on the fitting of DAPP was taken into account.3. DAPP was determined under three fibre conditions: (1) long sarcomere spacing (3-6-3-8 ,tm) at 16°C, (2) long sarcomere spacing at 22°C, and (3) normal sarcomere spacing (2-4-2-7 ium) at 22 'C. The average values for DAPP under these conditions were: (1) 0-12 (n=5); (2) 0-17 (n=5); and (3) 0-15 (n=7)x10-6cm2 s-1. The average value at 22°C, 0.16 x 10-6 cm2 S-1, is about 4 times smaller than values for myoglobin diffusivity at 20 'C commonly assumed in models of facilitated transport of oxygen by myoglobin.4. In order to test the possibility that the unexpectedly low value of DAPP found in intact fibres might be due to the binding of myoglobin to relatively immobile sites in myoplasm, experiments were carried out in a cut-fibre preparation using a technique described by Maylie, Irving, Sizto & Chandler (1987 b) for determining the diffusion constants and degree of myoplasmic binding of absorbance dyes. Values for DAPP and the factor (denoted 1+,8) by which the total myoglobin concentration exceeded the free myoglobin concentration were obtained by fitting the absorbance data by solutions of the one-dimensional diffusion equation. The average value S. M. BA YLOR AND P. C. PAPE (n = 4) for 1 + , ranged from 1P02 to 1-24, depending on the rate assumed for metMb reduction in cut fibres. Even the highest estimate of 1 +,f is much lower than the value of 4 required in order to attribute the small value of DAPP measured in intact fibres to the presence of bound (and immobile) myoglobin.5. Experiments were also performed in intact fibres to test whether possible convective movements of myoplasm associated with the mechanical events of muscle contraction might enhance DAPP. No significant increase in DAPP was observed when fibres were either tetanically s...

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Section: Introductionmentioning

confidence: 99%

Measurement of myoglobin diffusivity in the myoplasm of frog skeletal muscle fibres.

Baylor

Pape

1988

The Journal of Physiology

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“…These models have been extensively applied, critically examined (Kreuzer, 1982;Piiper and Scheid, 1986), and variously extended (Groebe, 1990;Honig et al, 1984;Lagerlund and Low, 1987;Mainwood and Rakusan, 1982;Popel and Gross, 1979). In particular, numerous authors have incorporated myoblobin-facilitated diffusion of oxygen (Baylor and Pape, 1988;de Koning et al, 1981;Fletcher, 1980;Gonzalez-Fernandez and Atta, 1982;Kreuzer and Hoofd, 1984;Loiselle, 1987;Murray, 1974;Salathe and Kolkka, 1986;Stroeve, 1982), the kinetics of oxygen-hemoglobin (Brittain and Simpson, 1989;Clark et al, 1985), or oxygen-myoglobin (van Ouwerkerk, 1977) interaction and the dependence of mitochondrial oxygen consumption on oxygen partial pressure (de Koning et al, 1980;Loiselle, 1982;Taylor and Murray, 1977). In addition, diffusion shunting of oxygen between adjacent capillaries (Grunewald and Sowa, 1978) or between distribution and drainage vessels (Piiper et al, 1984) has been considered.…”

Section: Discussionmentioning

confidence: 99%

Oxygen exchange in the isolated, arrested guinea pig heart: theoretical and experimental observations

Mawson

Hunter

Kenwright

et al. 1994

Biophysical Journal

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A model of oxygen transport in perfused myocardial tissue is presented. Steady-state conditions are assumed in order to mimic the metabolic rate of the arrested heart. The model incorporates Michaelis-Menten dependence of mitochondrial oxygen consumption, oxymyoglobin saturation and oxyhemoglobin saturation on oxygen partial pressure (PO2). The transport equations model both the advective supply of oxygen via the coronary circulation and the diffusive exchange of oxygen between tissues and environment across the epicardial and endocardial surfaces. The left ventricle is approximated by an axisymmetric prolate spheroid and the transport equations solved numerically using finite element techniques. Solution yields the PO2 profile across the heart wall. Integration of this profile yields the simulated rate of metabolic oxygen uptake determined according to the Fick principle. Correction for the diffusive flux of oxygen across the surfaces yields the simulated true metabolic rate of oxygen consumption. Simulated values of oxygen uptake are compared with those measured experimentally according to the Fick principle, using saline-perfused, Langendorff-circulated, K(+)-arrested, guinea pig hearts. Four perfusion variables were manipulated: arterial PO2, environmental PO2, coronary flow and perfusion pressure. In each case agreement between simulated and experimentally determined rates of oxygen consumption gives confidence that the model adequately describes the advective and diffusive transport of oxygen in the isolated, arrested, saline-perfused heart.

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“…At these low oxygen tensions, the demand of cells is not met even when the oxygen tension is greater than zero, and oxygen consumption is a continuous function of oxygen concentration that reaches zero when oxygen concentration is zero. Many studies investigating low oxygen concentration within tissue [5][6][7] have modelled oxygen consumption using a step function instead of a continuous function of oxygen concentration. Using the step function approach, the oxygen consumption is a positive constant where oxygen concentration is greater than zero, and oxygen consumption is zero where the oxygen concentration is zero.…”

Section: Introductionmentioning

confidence: 99%

“…Studies on oxygen transport to tissue have often neglected diffusion of oxygen through tissue in the direction of the capillary bloodflow, commonly known as axial diffusion [7,10,11]. This is an attractive simplification as the governing equations then simplify to a system of ordinary differential equations.…”

Section: Introductionmentioning

confidence: 99%