Diffusion coefficients of CO2 molecule and bicarbonate ion in hemoglobin solution measured by fluorescence technique.

Uchida, Katsuo; Mochizuki, Mayumi; Niizeki, Kyuichi

doi:10.2170/jjphysiol.33.619

Cited by 16 publications

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“…A computer program made by KAGAWA and MOCHIzulu (1984) was used for solving a partial differential equations for the C02 diffusion and the HC03-shift in a disc model with 3.5µm radius and 1.6 µm thickness. From the data of UCHIDA et al (1983), the intracellular diffusion coefficients of C02 and HC03-were assumed to be 0.34x 10 and 0.14 x 10 cm2/ sec, respectively. The transfer coefficient for C02 was newly obtained by KAGAWA and MocxizuKi (1984) by referring to both the data of NIIZEKI et al(1983) and the present study as 2.5 x 10-6 cm/sec/Torr.…”

Section: Methodsmentioning

confidence: 99%

Secondary CO2 diffusion following HCO3- shift across the red blood cell membrane.

1984

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In order to clarify the interaction between C02 diffusion and HC03-shift in the red blood cell (RBC), HC03-shift was measured by using a stopped flow method combined with fluorometry. When HC03-entered the RBC, the intracellular Pco2 increased, causing a secondary outflow of C02. Conversely, when HC03-ions flowed out of the RBC, the resulting decrease of PC02 caused an inward C02 diffusion. The Pco2 change caused by the inward HC03-shift was about 3-to 4-fold that of the outward shift. During the respective in-and outward-shifts, the mean half times of the extracellular pH changes were 0.15 and 0.13 sec. These were approximately twice as long as those of the primary C02 diffusion. The permeability of HC03-across the RBC membrane was obtained by comparing the experimental extracellular pH curve with a numerical solution for C02 and HC03-diffusions accompanied by the hydration and dehydration reactions. Thus the HC03-permeability was determined to be 5>< 10-4 and 7>< 10-4 cm/sec, in the in-and outward-HC03-shifts, respectively. The influence of Cl-concentration on HC03-permeability was tested by reducing the initial Cl-gradient across the RBC membrane. In a physiological Cl-concentration range the HC03-permeability was not affected by the Cl-gradient.Key Words:HC03-shift, C02 diffusion, HC03-permeability, stopped flow method, Cl-shift.In studies to elucidate the rate of gas exchange in vivo, the HC03-permeability across the red blood cell (RBC) membrane is an important parameters. KLOCKE (1976) measured the HC03-shift in RBC suspension by inhibiting the activity of carbonic anhydrase by using acetazolamide. However, because this enzyme is very active inside the RBC (KERNOHAN et a!., 1963), the rate of HC03-shift in the normal RBC seemed not to obey the rate measured in the suspension containing acetazolamide. Thus, we attempted to measure the rate of HC03-shift through extracellular pH by adding carbonic anhydrase into the normal RBC suspension. During the course of the pH measurement using a stopped flow apparatus, it was found that the intracellular HC03-change resulted in the Pco 2 change, causing a secondary C02 diffusion. Thus, from a recorded extracellular pH change which resulted from both the changes in Pco 2 and HC03 we attempted to determine HC03 -permeability. First, by varying the permeability a numerical solution for extracellular pH change was derived from the C02 diffusion equations accompanying the HC03-shift. Then, by comparing the computed pattern with the measured one, HC03-permeability was determined in terms of the transfer coefficient, rj-(HC03-). To obtain a numerical solution of the diffusion equation, estimated the diffusion coefficients for C02 and HC03r inside the RBC, and NnzEKI et al. (1983) measured the transfer coefficient for C02, 'j(C02) across the RBC membrane. SHIM0ucHI et al. (1984) clarified that the Pco2 change caused by the HC03 shift could be computed by a modified Henderson-Hasselbalch equation. Using these parameter values, KAGAWA and MocHlzuKi (1984) obtained...

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Section: Methodsmentioning

confidence: 99%

Secondary CO2 diffusion following HCO3- shift across the red blood cell membrane.

1984

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“…where a' and (aD)* are the slope of the C02 dissociation curve in the red cell and the combined diffusion constant, aDCo2+(a'-a)Dxco3 respectively (UCHIDA et al, 1983). The model had a radius of 3.5 ,gym, and a thickness of 1.6 ,um.…”

Section: Methodsmentioning

confidence: 99%

“…For analyzing the influence of oxygenation of the red cell to the C02 diffusion we have measured the relations between C02 content, pH, and Pcoz MocHIZUKI et al, 1983;TAZAWA et al, 1983) and also the diffusion coefficients of C02 and HC03 in a hemoglobin layer (UCHIDA et a!.,1983).…”

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“…In the present experiments an attempt was made to measure the rate of CO2 diffusion into and out of the red cell of human blood using a modified stopped flow apparatus with pH-sensitive fluorescence of 4-methylumbelliferone. The suspension was diluted to 7.5 % hematocrit, since the fluorescence around 450 nm absorbed by hemoglobin (UCHIDA et a!., 1983). Because of high accuracy and rapid response of the fluorescence, it became possible to obtain the continuous pH change due to the change in PC02.…”

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Rate of CO2 diffusion in the human red blood cell measured with pH-sensitive fluorescence.

1983

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The diffusion rate of C02, into and out of the red cell, was measured by using a stopped flow method with pH-sensitive fluorescence of 4-methylumbelliferone. A red cell suspension of 15 % hematocrit with the Pco2 of 8 Torr (or 65 Torr) was mixed with the same amount of saline solution having 65 Torr (or 8 Torr). Carbonic anhydrase was added to the external solution at a concentration of 20 mg/100 ml in order to accelerate the hydration and dehydration reactions, so that the Pcoz change in the fluid could be observed instantaneously through pH. In the inward diffusion Pcoz showed a large change, suggesting a lack of HC03-shift across the red cell membrane. In the outward diffusion, however, the PC0, change was smaller, suggesting that H+ ions produced in the external solution by C02 hydration were rapidly buffered by the red cell. The half times of the inward and outward diffusions were, on an average, 0.08 and 0.13 sec, respectively. The results of the simulation revealed that the above difference in half times was attributed to the difference in slope between the two dissociation curves with and without the HC03--shift. The diffusion rate was almost constant and remained independent of the direction of C02 flux. That is, at a low pH range the permeation of H+ ions across the red cell membrane was much faster than the diffusion rate of C02.

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“…C02 solubilities in RBC and saline solution are the values reported by VAN SLYKE et al (1928) andBARTELS et al (1959). The diffusion coefficients for C02 and HC03-, D(C02), and D(HC03-) were cited from UCHIDA et al (1983). The i2(C02) thereof was obtained from the extracellular Pc02 change during the inward C02 diffusion and outward HC03-shift, and was used for determining the inward ~(HC03-).…”

Section: Derivation Of Numerical Solutionmentioning

confidence: 99%

Numerical solution of partial differential equations for CO2 diffusion accompanying HCO3- shift in red blood cells.

Kagawa¹,

Mochizuki²

1984

Jpn.J.Physiol

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A computer program for a numerical solution of the C02 diffusion in the red blood cell including the HC03-shift was developed. Comparing the calculated extracellular Pco 2 curve with the experimental data on the primary and secondary C02 diffusions, the permeabilities of C02 and HC03-across the red cell membrane, i2(C02) and i(HC03-), were determined as i2(C02)=2.5 x 10-6 cm/(sec . Torr), Inward i(HC03-) =5 x 10-4 cm/sec , Outward ~(HC03-)=7 x 10-4 cm/sec. The dependencies of the C02 diffusion rate on the hematocrit and initial intraand extracellular HC03-concentrations were examined using the above permeabilities. The half-time of the extracellular PC02 change in a closed RBC suspension was obviously reduced as the hematocrit and initial extracellular HC03-increased, while the effect of the initial intracellular HC03-was not significant. The C02 diffusion in vivo was simulated using pulmonary and tissue capillary models. The half-time of the extracellular HC03-change was about 0.15 sec, while that of the intracellular HC03-change ranged from 40 to 60 msec. Despite the considerable interest in the interaction of CO2 and 02 diffusions into and out of the red blood cells (RBC), the C02 diffusion process into the RBC has not been explained theoretically. Insofar as the two compartment model (HILL et al., 1973;FORSTER and CRANDALL, 1975) was used, the above interaction cannot be calculated. KERNOHAN et al. (1963) reported that the C02 hydration and dehydration reactions occur so fast in the RBC that the chemical equilibrium is established within 1 msec. Therefore, because the intracellular Pco2 change is mainly limited by the C02 and HC03-diffusions, we attempted to solve the differential equations for the diffusion numerically in a disc RBC model. In an effort to obtain a numerical solution, NIIZEKI et al. (1983) measured the diffusion rate of C02 in the RBC in a closed RBC suspension. In their experiment on the

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Diffusion coefficients of CO2 molecule and bicarbonate ion in hemoglobin solution measured by fluorescence technique.

Cited by 16 publications

References 16 publications

Secondary CO2 diffusion following HCO3- shift across the red blood cell membrane.

Secondary CO2 diffusion following HCO3- shift across the red blood cell membrane.

Rate of CO2 diffusion in the human red blood cell measured with pH-sensitive fluorescence.

Numerical solution of partial differential equations for CO2 diffusion accompanying HCO3- shift in red blood cells.

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