title: Effect of extracellular ATP on contraction, cytosolic calcium activity, membrane voltage and ion currents of rat mesangial cells in primary culture.
abstract: 1. The effects of extracellular ATP on contraction, membrane voltage (Vm), ion currents and intracellular calcium activity [Ca2+]i were studied in rat mesangial cells (MC) in primary culture. 2. Addition of extracellular ATP (10(-5) and 10(-4) M) to MC led to a cell contraction which was independent of extracellular calcium. 3. Membrane voltage (Vm) and ion currents were measured with the nystatin patch clamp technique. ATP induced a concentration-dependent transient depolarization of Vm (ED50: 2 x 10(-6) M). During the transient depolarization ion currents were monitored simultaneously and showed an increase of the inward- and outward current. 4. In a buffer with a reduced extracellular chloride concentration (from 145 to 30 mM) ATP induced a depolarization augmented to -4 +/- 4 mV. 5. ATP-gamma-S and 2-methylthio-ATP depolarized Vm to the same extent as ATP, whereas alpha,beta-methylene-ATP (all 10(-5) M) had no effect on Vm. 6. The Ca2+ ionophore, A23187, depolarized Vm transiently from -51 +/- 2 to -28 +/- 4 mV and caused an increase of the inward current. 7. The intracellular calcium activity [Ca2+]i was measured with the fura-2 technique. ATP stimulated a concentration-dependent increase of [Ca2+]i (ED50: 5 x 10(-6) M). The increase of [Ca2+]i was biphasic with an initial peak followed by a sustained plateau. 8. The [Ca2+]i peak was still present in an extracellular Ca(2+)-free buffer, whereas the plateau was abolished. Verapamil (10(-4) M) did not inhibit the [Ca2+]i increase induced by ATP. 9. The data indicate that extracellular ATP contracts MC and is able to increase [Ca2+]i by the release of Ca2+ from intracellular stores and recruitment from the extracellular space. In addition ATP depolarizes Vm of MC by activating a Cl- conductance. The ATP-induced depolarization is mediated by a P2y receptor.
authors.affiliation: Department of Medicine, Albert-Ludwigs-University, Freiburg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Pavenstädt
authors.forename: J
authors.initials: J
authors.lastname: Gloy
authors.forename: J
authors.initials: J
authors.lastname: Leipziger
authors.forename: B
authors.initials: B
authors.lastname: Klär
authors.forename: J
authors.initials: J
authors.lastname: Pfeilschifter
authors.forename: P
authors.initials: P
authors.lastname: Schollmeyer
authors.forename: R
authors.initials: R
authors.lastname: Greger
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009761:Nystatin / Q000494:pharmacology; D051381:Rats; D011983:Receptors, Purinergic / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002712:Chlorides; D007473:Ion Channels; D011983:Receptors, Purinergic; D009761:Nystatin; D000001:Calcimycin; D000255:Adenosine Triphosphate; D014700:Verapamil; D002118:Calcium