title: P2Y(2) receptor-mediated inhibition of amiloride-sensitive short circuit current in M-1 mouse cortical collecting duct cells.
abstract: Extracellular nucleotides modulate renal ion transport. Our previous results in M-1 cortical collecting duct cells indicate that luminal and basolateral ATP via P2Y2 receptors stimulate luminal Ca2+-activated Cl- channels and inhibit Na+ transport. Here we address the mechanism of ATP-mediated inhibition of Na+ transport. M-1 cells had a transepithelial voltage (V(te)) of -31.4 +/- 1.3 mV and a transepithelial resistance (R(te)) of 1151 +/- 28 Omegacm(2). The amiloride-sensitive short circuit current (I(sc)) was -28.0 +/- 1.1 microA/cm2. The ATP-mediated activation of Cl- channels was inhibited when cytosolic Ca2+ increases were blocked with cyclopiazonic acid (CPA). Without CPA the ATP-induced [Ca2+](i) increase was paralleled by a rapid and transient R(te) decrease (297 +/- 51 Omegacm(2)). In the presence of CPA, basolateral ATP led to an R(te) increase by 144 +/- 17 Omegacm(2) and decreased V(te) from -31 +/- 2.6 to -26.6 +/- 2.5 mV. Isc dropped from -28.6 +/- 2.4 to -21.6 +/- 1.9 microA/cm2. Similar effects were observed with luminal ATP. In the presence of amiloride, ATP was without effect. This reflects ATP-mediated inhibition of Na+ absorption. Lowering [Ca2+](i) by removal of extracellular Ca2+ did not alter the ATP effect. PKC inhibition or activation were without effect. Na+ absorption was activated by pH(i) alkalinization and inhibited by pH(i) acidification. ATP slightly acidified M-1 cells by 0.05 +/- 0.005 pH units, quantitatively not explaining the ATP-induced effect. In summary this indicates that extracellular ATP via luminal and basolateral P2Y2 receptors inhibits Na+ absorption. This effect is not mediated via [Ca2+](i), does not involve PKC and is to a small part mediated via intracellular acidification.
authors.affiliation: Physiologisches Institut, Albert-Ludwigs-Universität, Hermann-Herder-Strasse 7, 79104 Freiburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Thomas
authors.forename: P
authors.initials: P
authors.lastname: Deetjen
authors.forename: W H
authors.initials: WH
authors.lastname: Ko
authors.forename: C
authors.initials: C
authors.lastname: Jacobi
authors.forename: J
authors.initials: J
authors.lastname: Leipziger
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D018118:Chloride Channels / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007211:Indoles / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D007672:Kidney Cortex / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058473:Receptors, Purinergic P2Y2; D019459:Urothelium / Q000166:cytology / Q000187:drug effects / Q000502:physiology*
chemical_list: D002121:Calcium Channel Blockers; D018118:Chloride Channels; D007211:Indoles; C546386:P2ry2 protein, mouse; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D000584:Amiloride; D000255:Adenosine Triphosphate; D002118:Calcium; C000543:cyclopiazonic acid