title: Radiotracer studies of cystic fibrosis transmembrane conductance regulator expressed in Xenopus oocytes.
abstract: We measured fluxes of radiotracers in Xenopus oocytes expressing the cystic fibrosis transmembrane conductance regulator (CFTR). Addition of adenosine 3',5'-cyclic monophosphate (cAMP)-elevating agents [forskolin and 3-isobutyl-1-methylxanthine (I/F)] led to large increases in uptake of 36Cl, 125I, and 82Br into oocytes expressing wild-type CFTR or delta F508 CFTR but not sham-injected oocytes. I/F also stimulated halide efflux from CFTR and delta F508 oocytes in the sequence Cl > Br > I. cAMP-induced increases in 36Cl efflux from delta F508 oocytes were approximately 20% of those in CFTR oocytes. Increases in halide efflux were blocked by diphenylamine-2-carboxylic acid but not by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. The phorbol ester, phorbol 12-myristate 13-acetate, also stimulated 36Cl efflux from CFTR oocytes. ATP uptakes into CFTR and sham oocytes were similar, and both were reduced by I/F. However, ATP uptake into I/F-treated CFTR oocytes was slightly greater (approximately 40%) than into I/F-treated sham oocytes. Urea uptake into CFTR and sham oocytes was similar and in both cases was increased by I/F. However, the I/F-induced increase in urea uptake into CFTR oocytes was significantly greater than for sham oocytes. I/F stimulated formate uptake into CFTR oocytes but not into sham oocytes. Fluxes of 22Na, 86Rb, 35SO4, 32PO4, and mannitol were unaltered by expression and activation of CFTR.
authors.affiliation: Department of Physiology, University of California, San Francisco 94143.
authors.forename: T
authors.initials: T
authors.lastname: Ohrui
authors.forename: W
authors.initials: W
authors.lastname: Skach
authors.forename: M
authors.initials: M
authors.lastname: Thompson
authors.forename: J
authors.initials: J
authors.lastname: Matsumoto-Pon
authors.forename: C
authors.initials: C
authors.lastname: Calayag
authors.forename: J H
authors.initials: JH
authors.lastname: Widdicombe
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000493:pharmacokinetics; D000818:Animals; D000242:Cyclic AMP / Q000502:physiology; D003550:Cystic Fibrosis / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004573:Electrolytes / Q000378:metabolism; D005561:Formates / Q000493:pharmacokinetics; D008353:Mannitol / Q000493:pharmacokinetics; D008565:Membrane Proteins / Q000378:metabolism*; D009865:Oocytes; D011868:Radioisotopes; D012413:Rubidium / Q000493:pharmacokinetics; D013431:Sulfates / Q000493:pharmacokinetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014981:Xenopus
chemical_list: D004573:Electrolytes; D005561:Formates; D008565:Membrane Proteins; D011868:Radioisotopes; D013431:Sulfates; C030544:formic acid; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D008353:Mannitol; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D012413:Rubidium; D013755:Tetradecanoylphorbol Acetate; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid