Experiments performed on isolated intestinal segments from the marine teleost fish, the European flounder (Platichthys flesus), revealed that the intestinal epithelium is capable of secondary active HCO3(-) secretion in the order of 0.2-0.3 micromol x cm(-2) x h(-1) against apparent electrochemical gradient. The HCO3(-) secretion occurs via anion exchange, is dependent on mucosal Cl(-), results...

Mass-spectrometric disequilibrium analysis was applied to investigate CO2 uptake and HCO3 2 transport in cells and chloroplasts of the microalgae Dunaliella tertiolecta and Chlamydomonas reinhardtii, which were grown in air enriched with 5% (v/v) CO2 (high-Ci cells) or in ambient air (low-Ci cells). Highand low-Ci cells of both species had the capacity to transport CO2 and HCO3 , with maximum r...

Luminal acidification provides the strongest physiological stimulus for duodenal HCO3- secretion. Various neurohumoral mechanisms are believed to play a role in acid-stimulated HCO3- secretion. Previous studies in the rat and human duodenum have shown that guanylin and Escherichia coli heat-stable toxin, both ligands of the transmembrane guanylyl cyclase receptor [guanylate cyclase C (GC-C)], a...

BACKGROUND The aim of the study was to test the hypothesis that in the fasting state, proximal intestinal HCO3- absorption, which depends on villus Na+/H+ exchanger activity, is tonically inhibited by a cholinergic atropine sensitive mechanism. SUBJECTS The experiments were performed in 34 healthy volunteers and in eight patients with intestinal villus atrophy. METHODS HCO3- absorption was ...

We have developed a technique to measure the fluorescence of a pH-sensitive dye (2,7-biscarboxyethyl-5(6)-carboxyfluorescein) in single glomerular mesangial cells in culture. The intracellular fluorescence excitation ratio of the dye was calibrated using the nigericin-high-K+ approach. In the absence of CO2-HCO3-, mesangial cells that are acid loaded by an NH+4 prepulse exhibit a spontaneous in...

The pancreatic duct secretes alkaline fluid that is rich in HCO3- and poor in Cl-. The molecular mechanisms that mediate ductal secretion and are responsible for the axial gradients of Cl- and HCO3- along the ductal tree are not well understood because H+ and HCO3- transport by duct cells have not been characterized or localized. To address these questions, we microdissected the intralobular, m...

The medullary collecting duct (MCD) from renal outer medulla possesses significant HCO3 absorptive capacity. In vitro microperfusion studies have shown that HCO3 absorption in this segment is carbonic anhydrase dependent, affected by peritubular and luminal chloride concentrations, is independent of the presence of Na or the presence of Na transport, and is stimulated by mineralocorticoid hormo...

The ability to move acid/base equivalents across the membrane of identified glial cells was investigated in isolated segmental ganglia of the leech Hirudo medicinalis. The intracellular pH (pHi) of the glial cells was measured with double-barreled, neutral-ligand, ion-sensitive microelectrodes during step changes of the external pH (pHo 7.4-7.0). The rate of intracellular acidification after th...

Bicarbonate (HCO3(-)) is an abundant anion that regulates extracellular and intracellular pH. Here, we use patch-clamp techniques to assess regulation of hippocampal CA3 pyramidal cell excitability by HCO3(-) in acute brain slices from C57BL/6 mice. We found that increasing HCO3(-) levels enhances action potential (AP) generation in both the soma and axon initial segment (AIS) by reducing Kv7/K...

OBJECTIVE To investigate whether serum bicarbonate (HCO3) levels can be used to accurately diagnose diabetic ketoacidosis (DKA) and classify its severity in children with new-onset diabetes mellitus (NODM). METHODS Retrospective study of all patients with NODM presenting to Boston Children's Hospital from October 1, 2007, to July 1, 2013. DKA was defined as blood glucose ≥200 mg/dL, venous pH...