title: Role of cyclic ADP-ribose in ATP-activated potassium currents in alveolar macrophages.
abstract: There is growing evidence that extracellular ATP causes a dramatic change in the membrane conductance of a variety of inflammatory cells. In the present study, using the nystatin perforated patch recording configuration, we found that ATP (0.3-30 microM) induced a transient outward current in a concentration-dependent manner and that the reversal potential of the ATP-induced outward current was close to the K+ equilibrium potential, indicating that the membrane behaves like a K+ electrode in the presence of ATP. The first application of ATP to alveolar macrophages perfused with Ca2+-free external solution could induce the outward current, but the response to ATP was diminished with successive applications. Intracellular perfusion with a Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N', N'-tetraacetic acid, also diminished the response. When cyclic ADP-ribose (cADPR) was applied to the macrophage cytoplasm, a transient outward current was elicited. Thereafter, the successive outward current was inhibited, suggesting the involvement of cADPR in the response. Intracellular perfusion with inositol 1,4, 5-trisphosphate also induced a transient outward current, but the successive current was not inhibited. The ATP-induced outward current was abolished when 8-amino-cADPR (as a blocker of cADPR, 10(-6)-10(-5) M) was introduced into the cytoplasm. Homogenates of alveolar macrophages showed both ADP-ribosyl cyclase and cADPR hydrolase activities, and CD38 (ADP-ribosyl cyclase/cADPR hydrolase) expression was confirmed by reverse transcriptase-polymerase chain reaction and Western blot analyses. These results indicate that ATP activates K+ currents by releasing Ca2+ from cADPR-sensitive internal Ca2+ stores.
authors.affiliation: First Department of Internal Medicine, Tohoku University School of Medicine, Sendai 980-77, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ebihara
authors.forename: T
authors.initials: T
authors.lastname: Sasaki
authors.forename: W
authors.initials: W
authors.lastname: Hida
authors.forename: Y
authors.initials: Y
authors.lastname: Kikuchi
authors.forename: T
authors.initials: T
authors.lastname: Oshiro
authors.forename: S
authors.initials: S
authors.lastname: Shimura
authors.forename: S
authors.initials: S
authors.lastname: Takasawa
authors.forename: H
authors.initials: H
authors.lastname: Okamoto
authors.forename: A
authors.initials: A
authors.lastname: Nishiyama
authors.forename: N
authors.initials: N
authors.lastname: Akaike
authors.forename: K
authors.initials: K
authors.lastname: Shirato
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000008:administration & dosage / Q000378:metabolism*; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D018999:Charybdotoxin / Q000494:pharmacology; D036563:Cyclic ADP-Ribose; D004305:Dose-Response Relationship, Drug; D016676:Macrophages, Alveolar / Q000378:metabolism*; D009761:Nystatin / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism*; D011802:Quinidine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015290:Second Messenger Systems; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D018999:Charybdotoxin; D036563:Cyclic ADP-Ribose; D009761:Nystatin; D000246:Adenosine Diphosphate Ribose; D001030:Apamin; D019789:Tetraethylammonium; D000255:Adenosine Triphosphate; D011802:Quinidine; D002118:Calcium