Extracellular UTP stimulates electrogenic bicarbonate secretion across CFTR knockout gallbladder epithelium.
The loss of cystic fibrosis transmembrane conductance regulator (CFTR)-mediated transepithelial HCO(3)(-) secretion contributes to the pathogenesis of pancreatic and biliary disease in cystic fibrosis (CF) patients. Recent studies have investigated P2Y(2) nucleotide receptor agonists, e.g., UTP, as a means to bypass the CFTR defect by stimulating Ca(2+)-activated Cl(-) secretion. However, the value of this treatment in facilitating transepithelial HCO(3)(-) secretion is unknown. Gallbladder mucosae from CFTR knockout mice were used to isolate the Ca(2+)-dependent anion conductance during activation of luminal P2Y(2) receptors. In Ussing chamber studies, UTP stimulated a transient peak in short-circuit current (I(sc)) that declined to a stable plateau phase lasting 30-60 min. The plateau I(sc) after UTP was Cl(-) independent, HCO(3)(-) dependent, insensitive to bumetanide, and blocked by luminal DIDS. In pH stat studies, luminal UTP increased both I(sc) and serosal-to-mucosal HCO(3)(-) flux (J(s-->m)) during a 30-min period. Substitution of Cl(-) with gluconate in the luminal bath to inhibit Cl(-)/HCO(3)(-) exchange did not prevent the increase in J(s-->m) and I(sc) during UTP. In contrast, luminal DIDS completely inhibited UTP-stimulated increases in J(s-->m) and I(sc). We conclude that P2Y(2) receptor activation results in a sustained (30-60 min) increase in electrogenic HCO(3)(-) secretion that is mediated via an intracellular Ca(2+)-dependent anion conductance in CF gallbladder.
Clarke
L L
LL
Dalton Cardiovascular Research Center and Departments of Veterinary Biomedical Sciences, University of Missouri-Columbia, 65211, USA. ClarkeL@missouri.edu
Harline
M C
MC
Gawenis
L R
LR
Walker
N M
NM
Turner
J T
JT
Weisman
G A
GA
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000367:Age Factors; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D003550:Cystic Fibrosis / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D004553:Electric Conductivity; D004594:Electrophysiology; D004847:Epithelial Cells / Q000378:metabolism; D005704:Gallbladder / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058473:Receptors, Purinergic P2Y2; D013268:Stimulation, Chemical; D014544:Uridine Triphosphate / Q000494:pharmacology*
D001639:Bicarbonates; D002712:Chlorides; C546386:P2ry2 protein, mouse; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium; D014544:Uridine Triphosphate