title: Active sulfate secretion by the intestine of winter flounder is through exchange for luminal chloride.
abstract: SO4(2-) transport by winter flounder intestine in Ussing chambers was characterized. With 50 mM SO4(2-) (physiological level) bathing the lumen, net absorption (lumen to blood) dominated. Under short-circuited conditions, 1 mM SO4(2-) on both sides, net active SO4(2-) secretion occurred (8.55 +/- 0.96 nmol. cm(-2). h(-1)). NaCN (10 mM), ouabain (10(-4) M), and luminal DIDS (0.2 mM) inhibited net secretion. Removal of luminal Cl- and HCO3- together (Cl--HCO3-) or Cl- alone blocked net secretion, whereas removal of luminal HCO3- alone increased net secretion. SO4(2-) uptake into foregut brush-border membrane vesicles was stimulated by a trans-Cl- gradient (in > out) and unaffected by a trans-HCO3- gradient (in > out). Short-circuiting with K+ (in = out) and valinomycin had no effect on Cl--stimulated SO4(2-) uptake, suggesting electroneutral exchange. Satiety (i.e., full stomach) stimulated the unidirectional absorptive flux, eliminating net secretion. It was concluded that the intestine is a site of SO4(2-) absorption in marine teleosts and that active SO4(2-) secretion is in exchange for luminal Cl-.
authors.affiliation: Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269, USA.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Pelis
authors.forename: J Larry
authors.initials: JL
authors.lastname: Renfro
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000042:Absorption / Q000187:drug effects; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism*; D004553:Electric Conductivity; D005399:Fishes / Q000378:metabolism*; D005502:Food; D005947:Glucose / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000187:drug effects; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012966:Sodium Cyanide / Q000494:pharmacology; D013431:Sulfates / Q000378:metabolism*; D013997:Time Factors; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D002712:Chlorides; D013431:Sulfates; D014634:Valinomycin; D010042:Ouabain; D005947:Glucose; D012966:Sodium Cyanide; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium