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Effect of Aquaporin 5 and Carbonic Anhydrase II on the Diffusion of CO 2 in Xenopus Oocytes
Author(s) -
Wang Dengke,
Boron Walter F
Publication year - 2019
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2019.33.1_supplement.544.18
Subject(s) - tris , chemistry , extracellular , xenopus , biophysics , oocyte , carbonic anhydrase , facilitated diffusion , permeability (electromagnetism) , membrane , chromatography , biochemistry , biology , enzyme , microbiology and biotechnology , embryo , gene
Transport of gases across the plasma membrane is not only dependent on the permeability, but also the concentration gradient. Carbon dioxide (CO 2 ) is one of the most important physiological gases in the human body, but undergoes slow hydration/dehydration reactions. As a gas channel, human (h) AQP5 can accelerate the diffusion of CO 2 by increasing membrane permeability to CO 2 . Carbonic anhydrases (CAs) also can accelerate the transport of CO 2 across the membrane by maximizing the CO 2 gradient via the consumption/production of CO 2 . Here, by measuring the maximal extracellular‐surface pH increase (DpH S ) caused by the introduction of extracellular CO 2 /HCO 3 − at constant extracellular pH (pH o ), we obtain a semiquantitative index of the CO 2 influx into Xenopus oocytes. On Day 1, we injected oocytes with the cRNA encoding hAQP5 (or H 2 O as a control). On Day 4, we injected purified bovine CA II protein in Tris buffer (or Tris buffer as a control). In agreement with previous reports, both hAQP5 and CA II individually increase DpH S vs. H 2 O/Tris‐injected control oocytes. However, the effect of CA II alone in raising DpH S even at very high CA II concentrations (1000ng/oocyte), is not as effective as AQP5 alone. Most likely, the native CO 2 permeability of Xenopus oocytes is so low that it limits transmembrane CO 2 diffusion. Interestingly, injection of CA II—even at CA II levels so low that they barely increase DpH S in oocytes not expressing AQP5—into oocytes expressing AQP5 causes DpH S to increase substantially vs. AQP5 oocytes without CA II. Our data suggest that when membrane CO 2 permeability is low, the effects of AQP5 and CA on CO 2 fluxes are supra‐additive. Support or Funding Information NIH U01‐GM111251, N00014‐15‐1‐2060, N00014‐16‐1‐2535 This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .