Extracellular ATP activates a P2 receptor in necturus erythrocytes during hypotonic swelling |
| |
Authors: | Light D B Dahlstrom P K Gronau R T Baumann N L |
| |
Institution: | (1) Department of Biology, Ripon College, 300 Seward St, Ripon, WI 54971, USA, US |
| |
Abstract: | We recently reported that ATP is released from Necturus erythrocytes via a conductive pathway during hypotonic swelling and that extracellular ATP potentiates regulatory volume
decrease (RVD). This study was designed to determine whether extracellular ATP exerts its effect via a purinoceptor. This
was accomplished using three different experimental approaches: 1) hemolysis studies to examine osmotic fragility, 2) a Coulter
counter to assess RVD, and 3) the whole-cell patch-clamp technique to measure membrane currents. We found extracellular ATP
and ATPγS, two P2 agonists, decreased osmotic fragility, enhanced cell volume recovery in response to hypotonic shock, and
increased whole-cell currents. In addition, 2-methylthio-ATP potentiated RVD. In contrast, UTP, α,β-methylene-ATP, and 2′-&
3′-O-(4-benzoyl-benzoyl) adenosine 5′-triphosphate and the P1 agonist adenosine had no effect regardless of experimental approach.
Furthermore, the P2 antagonist suramin increased osmotic fragility, inhibited RVD, and reduced whole-cell conductance in swollen
cells. Consistent with a previous study that indicated cell swelling activates a K+ conductance, suramin had no effect in the presence of gramicidin (a cationophore used to maintain a high K+ permeability). We also found the P2 antagonist pyridoxal-5-phosphate-6-azophenyl-2′4-disulfonic acid (PPADS) increased osmotic
fragility; however, reactive blue 2 and the P1 antagonists caffeine and theophylline had no effect. Our results show that
extracellular ATP activated a P2 receptor in Necturus erythrocytes during hypotonic swelling, which in turn potentiated RVD by stimulating K+ efflux. Pharmacological evidence suggested the presence of a P2X receptor subtype.
Received: 6 January 2001/Revised: 17 April 2001 |
| |
Keywords: | : Nucleotides — Purinoceptor — Suramin — Potassium channel — Cell volume regulation |
本文献已被 PubMed SpringerLink 等数据库收录! |
|