title: Ion transport across Xenopus alveolar epithelium is regulated by extracellular ATP, UTP and adenosine.
abstract: Native alveolar epithelium from Xenopus lung was used for electrophysiological Ussing chamber experiments to investigate ion transport regulation. The tissue exhibits a considerable absorption of Na(+) ions and this transepithelial transport is largely up-regulated after treatment of donor animals with ACTH. Extracellular ATP, UTP and adenosine were tested for their regulating effects and all three increased I(sc), which was mainly due to a stimulation of amiloride sensitive Na(+) transport (increase of I(ami) 32% for ATP, 21% for UTP, 25% for adenosine). Solely the effect of UTP was completely abolished in the presence of amiloride. In contrast, the effects of ATP or adenosine disappeared under Cl(-)-free conditions. ATP and UTP proved to have additive effects and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), an antagonist of purinergic receptors, inhibited selectively the effect of UTP on I(sc). Further, I(sc) was increased by the P2X selective agonist beta,gamma-meATP. We were able to demonstrate, that extracellular purines and pyrimidines play a possible role as auto/paracrine messengers for alveolar ion transport regulation in Xenopus lung.
authors.affiliation: Institute of Animal Physiology, Justus-Liebig-University Giessen, Wartweg 95, D-35392 Giessen, Germany. martin.fronius@bio.uni-giessen.de
authors.forename: Martin
authors.initials: M
authors.lastname: Fronius
authors.forename: Andreas
authors.initials: A
authors.lastname: Berk
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Clauss
authors.forename: Mikael
authors.initials: M
authors.lastname: Schnizler
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D004347:Drug Interactions; D005110:Extracellular Space / Q000187:drug effects; D005260:Female; D017136:Ion Transport / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques / Q000379:methods; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D020545:Respiratory Mucosa / Q000187:drug effects* / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D014544:Uridine Triphosphate / Q000494:pharmacology*; D014982:Xenopus laevis
chemical_list: D010975:Platelet Aggregation Inhibitors; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D000255:Adenosine Triphosphate; D000324:Adrenocorticotropic Hormone; D012964:Sodium; D000241:Adenosine; D014544:Uridine Triphosphate