Extracellular UTP stimulates electrogenic bicarbonate secretion across CFTR knockout gallbladder epithelium

• Published in: American journal of physiology: Gastrointestinal and liver physiology Vol. 279; no. 1; pp. G132 - G138
• Main Authors: Clarke, L L, Harline, M C, Gawenis, L R, Walker, N M, Turner, J T, Weisman, G A
• Format: Journal Article
• Language: English
• Published: United States 01.07.2000
• Subjects: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid - pharmacology; Age Factors; Animals; Bicarbonates - metabolism; Biological Transport - drug effects; Biological Transport - physiology; Calcium - metabolism; Chlorides - metabolism; Colforsin - pharmacology; Cystic Fibrosis - metabolism; Cystic Fibrosis Transmembrane Conductance Regulator - genetics; Electric Conductivity; Electrophysiology; Epithelial Cells - metabolism; Epithelial Cells - secretion; Gallbladder - metabolism; Gallbladder - secretion; Hydrogen-Ion Concentration; In Vitro Techniques; Membrane Potentials - drug effects; Membrane Potentials - physiology; Mice; Mice, Inbred C57BL; Mice, Knockout; Purinergic P2 Receptor Agonists; Receptors, Purinergic P2 - metabolism; Receptors, Purinergic P2Y2; Stimulation, Chemical; Uridine Triphosphate - pharmacology
• ISSN: 0193-1857; 1522-1547
• DOI: 10.1152/ajpgi.2000.279.1.G132

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.