title: Role of purinergic receptors in chloride secretion in Caco-2 cells.
abstract: Purinergic receptors play an important role in regulating Cl- secretion in epithelial cells. To explore further the role of these receptors in the intestine, we utilized the human intestinal epithelial cell line, Caco-2, grown on permeable membrane supports and assayed for Cl- secretion by measuring the short-circuit current (Isc). Stimulation of Isc by extracellular nucleotides could be detected by day 4 and increased by day 10 postseeding. The magnitude of stimulation of Isc at 10 microM in cells at day 10 was UTP > ATP > UDP > > 2-methylthioadenosine 5'-triphosphate (2-MeS-ATP) = ADP on the apical side and UTP = 2-MeS-ATP = ATP > ADP > > UDP on the basolateral side. Cross-desensitization studies suggested that two different receptors are expressed in the apical membrane, a P2U purinoceptor and a uridine nucleotide receptor. Two different receptors are also expressed in the basolateral membrane, a P2U receptor and another that reacts with both 2-MeS-ATP and ADP. This latter receptor has an unusual pharmacological profile, with a reactivity for 2-MeS-ATP > ADP but not for ATP. Responses to purinergic receptor agonists were inhibited by pretreatment with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, thapsigargin, or quinine. Thus we suggest that an increase in intracellular Ca2+ and subsequent opening of Ca(2+)-activated K+ channel play a role in increasing driving force for Cl- to exit across the apical membrane. The role of the cystic fibrosis transmembrane conductance regulator as a Cl- exit pathway on the apical membrane was also established.
authors.affiliation: Department of Physiology and Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: C N
authors.initials: CN
authors.lastname: Inoue
authors.forename: J S
authors.initials: JS
authors.lastname: Woo
authors.forename: E M
authors.initials: EM
authors.lastname: Schwiebert
authors.forename: T
authors.initials: T
authors.lastname: Morita
authors.forename: K
authors.initials: K
authors.lastname: Hanaoka
authors.forename: S E
authors.initials: SE
authors.lastname: Guggino
authors.forename: W B
authors.initials: WB
authors.lastname: Guggino
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000227:Adenine Nucleotides / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D002034:Bumetanide / Q000494:pharmacology; D018938:Caco-2 Cells; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002712:Chlorides / Q000378:metabolism*; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D007413:Intestinal Mucosa; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology*; D028021:Sodium-Potassium-Chloride Symporters; D014500:Uracil Nucleotides / Q000494:pharmacology*; D062367:ortho-Aminobenzoates / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D002121:Calcium Channel Blockers; D002352:Carrier Proteins; D002712:Chlorides; D011983:Receptors, Purinergic; D028021:Sodium-Potassium-Chloride Symporters; D014500:Uracil Nucleotides; D062367:ortho-Aminobenzoates; D002034:Bumetanide; D000255:Adenosine Triphosphate; C001209:fenamic acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D005905:Glyburide