The effects of changes in peritubular pH, carbon dioxide tension (PCO2), and HCO3- concentration on net HCO3- transport was examined in in vitro perfused cortical collecting tubules (CCTs) from unpretreated New Zealand white rabbits. Lowering peritubular HCO3- concentration and pH by reciprocal replacement of HCO3- with Cl-, significantly stimulated net HCO3- absorption. Lowering peritubular HC...

Bestrophin-1 (Best1) is a Cl(-) channel that is linked to various retinopathies in both humans and dogs. Dysfunction of the Best1 Cl(-) channel has been proposed to cause retinopathy because of altered Cl(-) transport across the retinal pigment epithelium (RPE). In addition to Cl(-), many Cl(-) channels also transport HCO3(-). Because HCO3(-) is physiologically important in pH regulation and in...

Address for Correspondence:Masaji Mochizuki, Minami-11, Nishi-20, 4-23 Chuo-Ku, Sapporo 064-0811, Japan The bicarbonate concentration in plasma , [HCO3], has a PCO2-dependent component, [HCO3]*, and a metabolic component, [HCO3]. The [HCO3]* in elderly patients and volunteers was expressed by an exponential function of PCO2 obtained by analysis of the venous-arterial (a-v) difference in [HCO3]....

Reduced gastrointestinal HCO3- secretion contributes to malabsorption and obstructive syndromes in cystic fibrosis. The apical HCO3- transport pathways in these organs have not been defined. We therefore assessed the involvement of apical Cl-/HCO3- exchangers and anion conductances in basal and cAMP-stimulated duodenal HCO3- secretion. Muscle-stripped rat and rabbit proximal duodena were mounte...

The equilibrium CO2+H2O right arrow over left arrow H++HCO3- had made it impossible to determine how isolated changes in basolateral CO2 ([CO2]) or HCO3- concentration ([HCO3-]), at a fixed basolateral pH, modulate renal HCO3- or reabsorption. In the present study, we have begun to address this issue by measuring HCO3- reabsorption (JHCO3) and intracellular pH (pHi) in isolated perfused rabbit ...

We have used pH-, Na-, and Cl-sensitive microelectrodes to study basolateral HCO3- transport in isolated, perfused proximal tubules of the tiger salamander Ambystoma tigrinum. In one series of experiments, we lowered basolateral pH (pHb) from 7.5 to 6.8 by reducing [HCO3-]b from 10 to 2 mM at a constant pCO2. This reduction of pHb and [HCO3-]b causes a large (approximately 0.35), rapid fall in ...

Bonanno, Joseph A., Yi Guan, Sergey Jelamskii, and Xiao Jun Kang. Apical and basolateral CO2-HCO3 2 permeability in cultured bovine corneal endothelial cells. Am. J. Physiol. 277 (Cell Physiol. 46): C545–C553, 1999.—Corneal endothelial function is dependent on HCO3 2 transport. However, the relative HCO3 2 permeabilities of the apical and basolateral membranes are unknown. Using changes in intr...

The SLC26 transporters are a family of mostly luminal Cl- and HCO3- transporters. The transport mechanism and the Cl-/HCO3- stoichiometry are not known for any member of the family. To address these questions, we simultaneously measured the HCO3- and Cl- fluxes and the current or membrane potential of slc26a3 and slc26a6 expressed in Xenopus laevis oocytes and the current of the transporters ex...

Colonic bicarbonate (HCO3(-)) secretion is a well-established physiological process that is closely linked to overall fluid and electrolyte movement in the mammalian colon. These present studies show that extracellular calcium-sensing receptor (CaSR), a fundamental mechanism for sensing and regulating ionic and nutrient compositions of extracellular milieu in the small and large intestine, regu...

Bonanno, Joseph A., Yi Guan, Sergey Jelamskii, and Xiao Jun Kang. Apical and basolateral CO2-HCO3 2 permeability in cultured bovine corneal endothelial cells. Am. J. Physiol. 277 (Cell Physiol. 46): C545–C553, 1999.—Corneal endothelial function is dependent on HCO3 2 transport. However, the relative HCO3 2 permeabilities of the apical and basolateral membranes are unknown. Using changes in intr...