Nucleotide regulation of paracellular Cl- permeability in natural rabbit airway epithelium.
In this study, we demonstrate a novel regulatory mechanism by which mucosal nucleotides via P2Y receptors decrease paracellular Cl(-) ion permeability in natural rabbit airway epithelium (in addition to a decrease in active Na(+) absorption). In contrast to primary cultures, the natural airway epithelium is a low-resistance epithelium, and an equivalent circuit model predicts that changes of more than approximately 12% in transepithelial conductance (G (t)) must include an effect on paracellular conductance (G (s)). Mucosal P2Y receptor stimulation with uridine triphosphate (UTP; 200 microM) decreased G (t) by up to 50% (average, 24%) and simultaneously decreased the paracellular Cl(-) permeability (mucosa-to-serosa Cl(-) flux) by 16%, but had no effect on mannitol permeability. The G (t) response to UTP was mimicked and attenuated by ionomycin (1 microM), suggesting a dependence on Ca(2+) (i). Amiloride (100 microM) and hyperosmolarity (+75 mM mannitol) also decreased G (t), indicating a role of cell shrinkage. Elevation of cAMP with forskolin (8 microM) or isoproterenol (10 microM) increased G (t) by 55 and 32%, and forskolin increased paracellular Cl(-) permeability by 37% without affecting mannitol permeability. The opposite effects of Ca(2+) (i) and cAMP on G (t) suggest an autocrine nucleotide signaling sequence where P2Y-dependent decrease in passive, paracellular Cl(-) transport is succeeded by a reversion of this effect due to P1-receptor-stimulated cAMP formation by adenosine originating from a time-dependent breakdown of mucosal ATP.
Poulsen
Asser Nyander
AN
Department of Medical Physiology, The Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark.
Klausen
Thomas Levin
TL
Pedersen
Peter Steen
PS
Willumsen
Niels Johannes
NJ
Frederiksen
Ole
O
D000262:Adenylyl Cyclases / Q000378:metabolism; D000584:Amiloride / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D048429:Cell Size; D002712:Chlorides / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008353:Mannitol / Q000378:metabolism; D009297:Nasal Mucosa / Q000166:cytology / Q000378:metabolism*; D010539:Permeability; D011817:Rabbits; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D026941:Sodium Channel Blockers / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism; D014544:Uridine Triphosphate / Q000378:metabolism*
D002712:Chlorides; D018048:Receptors, Purinergic P2; D026941:Sodium Channel Blockers; D008353:Mannitol; D000584:Amiloride; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D002118:Calcium; D014544:Uridine Triphosphate