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Am J Physiol Cell Physiol
2014 Nov 01;3079:C841-58. doi: 10.1152/ajpcell.00049.2014.
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Evidence from mathematical modeling that carbonic anhydrase II and IV enhance CO2 fluxes across Xenopus oocyte plasma membranes.
Occhipinti R
,
Musa-Aziz R
,
Boron WF
.
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Exposing an oocyte to CO2/HCO3 (-) causes intracellular pH (pHi) to decline and extracellular-surface pH (pHS) to rise to a peak and decay. The two companion papers showed that oocytes injected with cytosolic carbonic anhydrase II (CA II) or expressing surface CA IV exhibit increased maximal rate of pHi change (dpHi/dt)max, increased maximal pHS changes (ΔpHS), and decreased time constants for pHi decline and pHS decay. Here we investigate these results using refinements of an earlier mathematical model of CO2 influx into a spherical cell. Refinements include 1) reduced cytosolic water content, 2) reduced cytosolic diffusion constants, 3) refined CA II activity, 4) layer of intracellular vesicles, 5) reduced membrane CO2 permeability, 6) microvilli, 7) refined CA IV activity, 8) a vitelline membrane, and 9) a new simulation protocol for delivering and removing the bulk extracellular CO2/HCO3 (-) solution. We show how these features affect the simulated pHi and pHS transients and use the refined model with the experimental data for 1.5% CO2/10 mM HCO3 (-) (pHo = 7.5) to find parameter values that approximate ΔpHS, the time to peak pHS, the time delay to the start of the pHi change, (dpHi/dt)max, and the change in steady-state pHi. We validate the revised model against data collected as we vary levels of CO2/HCO3 (-) or of extracellular HEPES buffer. The model confirms the hypothesis that CA II and CA IV enhance transmembrane CO2 fluxes by maximizing CO2 gradients across the plasma membrane, and it predicts that the pH effects of simultaneously implementing intracellular and extracellular-surface CA are supra-additive.
Alessandrini,
Voltage-induced morphological modifications in oocyte membranes containing exogenous K+ channels studied by electrochemical scanning force microscopy.
2008, Pubmed,
Xenbase
Alessandrini,
Voltage-induced morphological modifications in oocyte membranes containing exogenous K+ channels studied by electrochemical scanning force microscopy.
2008,
Pubmed
,
Xenbase
Boron,
Sharpey-Schafer lecture: gas channels.
2010,
Pubmed
,
Xenbase
Boron,
Intrinsic CO2 permeability of cell membranes and potential biological relevance of CO2 channels.
2011,
Pubmed
Boron,
Intracellular pH transients in squid giant axons caused by CO2, NH3, and metabolic inhibitors.
1976,
Pubmed
Boron,
Intracellular pH transients in giant barnacle muscle fibers.
1977,
Pubmed
Delpire,
How carbonic anhydrases and pH buffers facilitate the movement of carbon dioxide through biological membranes. Focus on "Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase II enhances CO2 fluxes across Xenopus oocyte plasma membranes"; "Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase IV enhances CO2 fluxes across Xenopus oocyte plasma membranes"; and "Evidence from mathematical modeling that carbonic anhydrase II and IV e
2014,
Pubmed
Endeward,
Extra- and intracellular unstirred layer effects in measurements of CO2 diffusion across membranes--a novel approach applied to the mass spectrometric 18O technique for red blood cells.
2009,
Pubmed
Geers,
Carbon dioxide transport and carbonic anhydrase in blood and muscle.
2000,
Pubmed
Gros,
Proton transport by phosphate diffusion--a mechanism of facilitated CO2 transfer.
1976,
Pubmed
Lu,
Effect of human carbonic anhydrase II on the activity of the human electrogenic Na/HCO3 cotransporter NBCe1-A in Xenopus oocytes.
2006,
Pubmed
,
Xenbase
Missner,
Carbon dioxide transport through membranes.
2008,
Pubmed
Musa-Aziz,
Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase II enhances CO2 fluxes across Xenopus oocyte plasma membranes.
2014,
Pubmed
,
Xenbase
Musa-Aziz,
Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase IV enhances CO2 fluxes across Xenopus oocyte plasma membranes.
2014,
Pubmed
,
Xenbase
Nicholson,
Ion diffusion modified by tortuosity and volume fraction in the extracellular microenvironment of the rat cerebellum.
1981,
Pubmed
Nicholson,
Extracellular space structure revealed by diffusion analysis.
1998,
Pubmed
Roos,
Intracellular pH and distribution of weak acids across cell membranes. A study of D- and L-lactate and of DMO in rat diaphragm.
1975,
Pubmed
Roos,
Intracellular pH.
1981,
Pubmed
Schneider,
GPI-anchored carbonic anhydrase IV displays both intra- and extracellular activity in cRNA-injected oocytes and in mouse neurons.
2013,
Pubmed
,
Xenbase
Somersalo,
A reaction-diffusion model of CO2 influx into an oocyte.
2012,
Pubmed
,
Xenbase
Spitzer,
Facilitation of intracellular H(+) ion mobility by CO(2)/HCO(3)(-) in rabbit ventricular myocytes is regulated by carbonic anhydrase.
2002,
Pubmed
Swietach,
Tumor-associated carbonic anhydrase 9 spatially coordinates intracellular pH in three-dimensional multicellular growths.
2008,
Pubmed
Swietach,
The role of carbonic anhydrase 9 in regulating extracellular and intracellular ph in three-dimensional tumor cell growths.
2009,
Pubmed
Swietach,
Modelling intracellular H(+) ion diffusion.
2003,
Pubmed
Syková,
Diffusion in brain extracellular space.
2008,
Pubmed
Zampighi,
A method for determining the unitary functional capacity of cloned channels and transporters expressed in Xenopus laevis oocytes.
1995,
Pubmed
,
Xenbase
Zeuthen,
Mobility of ions, sugar, and water in the cytoplasm of Xenopus oocytes expressing Na(+)-coupled sugar transporters (SGLT1).
2002,
Pubmed
,
Xenbase
