title: The effect of 4,4'-diisothiocyanato-stilbene-2,2'-disulfonate on CO2 permeability of the red blood cell membrane.
abstract: It has long been assumed that the red cell membrane is highly permeable to gases because the molecules of gases are small, uncharged, and soluble in lipids, such as those of a bilayer. The disappearance of 12C18O16O from a red cell suspension as the 18O exchanges between labeled CO2 + HCO3- and unlabeled HOH provides a measure of the carbonic anhydrase (CA) activity (acceleration, or A) inside the cell and of the membrane self-exchange permeability to HCO3- (Pm,HCO-3). To test this technique, we added sufficient 4, 4'-diisothiocyanato-stilbene-2,2'-disulfonate (DIDS) to inhibit all the HCO3-/Cl- transport protein (Band III or capnophorin) in a red cell suspension. We found that DIDS reduced Pm,HCO-3 as expected, but also appeared to reduce intracellular A, although separate experiments showed it has no effect on CA activity in homogenous solution. A decrease in Pm,CO2 would explain this finding. With a more advanced computational model, which solves for CA activity and membrane permeabilities to both CO2 and HCO3-, we found that DIDS inhibited both Pm,HCO-3 and Pm,CO2, whereas intracellular CA activity remained unchanged. The mechanism by which DIDS reduces CO2 permeability may not be through an action on the lipid bilayer itself, but rather on a membrane transport protein, implying that this is a normal route for at least part of red cell CO2 exchange.
authors.affiliation: Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA. forster@mail.med.upenn.edu
authors.forename: R E
authors.initials: RE
authors.lastname: Forster
authors.forename: G
authors.initials: G
authors.lastname: Gros
authors.forename: L
authors.initials: L
authors.lastname: Lin
authors.forename: Y
authors.initials: Y
authors.lastname: Ono
authors.forename: M
authors.initials: M
authors.lastname: Wunder
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology*; D000328:Adult; D001457:Anion Exchange Protein 1, Erythrocyte / Q000187:drug effects / Q000378:metabolism*; D001639:Bicarbonates / Q000097:blood; D002245:Carbon Dioxide / Q000097:blood*; D002247:Carbon Isotopes; D002256:Carbonic Anhydrases / Q000097:blood; D002463:Cell Membrane Permeability / Q000187:drug effects*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000502:physiology*; D004912:Erythrocytes / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008954:Models, Biological; D008956:Models, Chemical; D010103:Oxygen Isotopes; D013997:Time Factors
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D001639:Bicarbonates; D002247:Carbon Isotopes; D010103:Oxygen Isotopes; D002245:Carbon Dioxide; D002256:Carbonic Anhydrases; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid