Acetazolamide inhibits stimulated feline liver and gallbladder bicarbonate secretion

Hepatobiliary acid-base homeostasis: Insights from analogous secretory epithelia

Many epithelia secrete bicarbonate-rich fluid to generate flow, alter viscosity, control pH and potentially protect luminal and intracellular structures from chemical stress. Bicarbonate is a key component of human bile and impaired biliary bicarbonate secretion is associated with liver damage. Major efforts have been undertaken to gain insight into acid-base homeostasis in cholangiocytes and more can be learned from analogous secretory epithelia. Extrahepatic examples include salivary and pancreatic duct cells, duodenocytes, airway and renal epithelial cells. The cellular machinery involved in acid-base homeostasis includes carbonic anhydrase enzymes, transporters of the solute carrier family, and intra- and extracellular pH sensors. This pH-regulatory system is orchestrated by protein-protein interactions, the establishment of an electrochemical gradient across the plasma membrane and bicarbonate sensing of the intra- and extracellular compartment. In this review, we discuss conserved principles identified in analogous secretory epithelia in the light of current knowledge on cholangiocyte physiology. We present a framework for cholangiocellular acid-base homeostasis supported by expression analysis of publicly available single-cell RNA sequencing datasets from human cholangiocytes, which provide insights into the molecular basis of pH homeostasis and dysregulation in the biliary system.

Neonatal Bartter syndrome with cholelithiasis and hydrocephalus: Rare association

Neonatal Bartter syndrome (NBS) is a rare autosomal recessive renal tubular disorder. This disease is characterized by hypokalemia, hypochloremia, and metabolic alkalosis that is often associated with failure to thrive and recurrent episodes of dehydration. The combination of BS and cholelithiasis in an infant is very rare. Herein, we report a premature male infant with NBS who developed cholelithiasis and hydrocephalus on clinical follow up. We recommend that periodic routine hepatobiliary ultrasonograpic screening for cholelithiasis should be performed in patients with NBS.

Electrogenic bicarbonate secretion by prairie dog gallbladder

Pathological rates of gallbladder salt and water transport may promote the formation of cholesterol gallstones. Because prairie dogs are widely used as a model of this event, we characterized gallbladder ion transport in animals fed control chow by using electrophysiology, ion substitution, pharmacology, isotopic fluxes, impedance analysis, and molecular biology. In contrast to the electroneutral properties of rabbit and Necturus gallbladders, prairie dog gallbladders generated significant short-circuit current (I(sc); 171 +/- 21 microA/cm(2)) and lumen-negative potential difference (-10.1 +/- 1.2 mV) under basal conditions. Unidirectional radioisotopic fluxes demonstrated electroneutral NaCl absorption, whereas the residual net ion flux corresponded to I(sc). In response to 2 microM forskolin, I(sc) exceeded 270 microA/cm(2), and impedance estimates of the apical membrane resistance decreased from 200 Omega.cm(2) to 13 Omega.cm(2). The forskolin-induced I(sc) was dependent on extracellular HCO(3)(-) and was blocked by serosal 4,4'-dinitrostilben-2,2'-disulfonic acid (DNDS) and acetazolamide, whereas serosal bumetanide and Cl(-) ion substitution had little effect. Serosal trans-6-cyano-4-(N-ethylsulfonyl-N-methylamino)-3-hydroxy-2,2-dimethyl-chroman and Ba(2+) reduced I(sc), consistent with the inhibition of cAMP-dependent K(+) channels. Immunoprecipitation and confocal microscopy localized cystic fibrosis transmembrane conductance regulator protein (CFTR) to the apical membrane and subapical vesicles. Consistent with serosal DNDS sensitivity, pancreatic sodium-bicarbonate cotransporter protein pNBC1 expression was localized to the basolateral membrane. We conclude that prairie dog gallbladders secrete bicarbonate through cAMP-dependent apical CFTR anion channels. Basolateral HCO(3)(-) entry is mediated by DNDS-sensitive pNBC1, and the driving force for apical anion secretion is provided by K(+) channel activation.

Expression of pituitary adenylate cyclase-activating polypeptide 1 and 2 receptor mRNA in gallbladder tissue of patients with gallstone or gallbladder polyps

AIM: To detect the expression of pituitary adenylate cyclase-activating polypeptide receptor 1 (VPCAP₁-R) and VPCAP₂-R mRNA in gallbladder tissues of patients with gallstone or gallbladder polyps.

METHODS: The expression of VPCAP₁-R and VPCAP₂-R mRNA in gallbladder tissues was detected in 25 patients with gallstone, 8 patients with gallbladder polyps and 7 donors of liver transplantation by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: The VPCAP₂-R mRNA expression level in the control group (1.09±0.58) was lower than that in the gallbladder polyp group (1.64 ± 0.56) and the gallstone group (1.55±0.45) (P < 0.05) while the VPCAP₁-R mRNA expression level in the control group (1.15 ± 0.23) was not apparently different from that in the gallbladder polyp group (1.28±0.56) and the gallstone group (1.27 ± 0.38).

CONCLUSION: The abnormal expression of VPCAP₂-R mRNA in gallbladder tissue may play a role in the formation of gallbladder stone and gallbladder polyps.