title: cAMP activates an ATP-conductive pathway in cultured shark rectal gland cells.
abstract: The molecular mechanisms associated with ATP transport and release into the extracellular milieu are largely unknown. To assess the presence of endogenous ATP-conductive pathway(s) in shark rectal gland (SRG) cells, patch-clamp techniques were applied to primary cultures of SRG cells. Whole cell currents were obtained with either intracellular tris(hydroxymethyl)aminomethane (Tris) or Mg2+ salts of ATP (200 mM nominal ATP) and 280 mM NaCl bathing solution. Basal currents showed a sizable ATP permeability for outward movement of MgATP. Adenosine 3',5'-cyclic monophosphate (cAMP) stimulation significantly increased the whole cell conductance (with either intracellular Tris-ATP or MgATP). Symmetrical whole cell ATP currents were also observed after cAMP activation, thus consistent with ATP as the main charge carrier. The cAMP-inducible ATP currents were insensitive to the Cl- channel blockers 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, diphenylamine-2-carboxylate, and anthracene-9-carboxylic acid but were readily blocked by nifedipine (400 microM) and glibenclamide (400 microM). The nature of the electrodiffusional ATP movement was further assessed by single-channel analysis of either MgATP or Tris-ATP currents in excised inside-out patches, both spontaneous and after activation with protein kinase A. Single-channel ATP currents were inhibited by either nifedipine or glibenclamide. Thus SRG cells express endogenous ATP-permeable pathways both before and after cAMP stimulation. Electrodiffusional ATP movement by SRG cells may play a significant role in the transport and delivery of cellular ATP to the extracellular milieu, which may help coordinate the dynamics of the epithelial secretory response in this cell model.
authors.affiliation: Renal Unit, Massachusetts General Hospital East, and Department of Medicine, Harvard Medical School, Charlestown 02129, USA.
authors.forename: H F
authors.initials: HF
authors.lastname: Cantiello
authors.forename: G R
authors.initials: GR
authors.lastname: Jackson
authors.forename: A G
authors.initials: AG
authors.lastname: Prat
authors.forename: J L
authors.initials: JL
authors.lastname: Gazley
authors.forename: J N
authors.initials: JN
authors.lastname: Forrest
authors.forename: D A
authors.initials: DA
authors.lastname: Ausiello
mesh_terms: D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D000242:Cyclic AMP / Q000502:physiology*; D004553:Electric Conductivity; D007473:Ion Channels / Q000502:physiology; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D012491:Salt Gland / Q000166:cytology / Q000502:physiology*; D012754:Sharks / Q000502:physiology*; D062367:ortho-Aminobenzoates / Q000494:pharmacology
chemical_list: D018118:Chloride Channels; D007473:Ion Channels; D062367:ortho-Aminobenzoates; D000255:Adenosine Triphosphate; C001209:fenamic acid; D000242:Cyclic AMP; D009543:Nifedipine