One of the major tasks of the renal proximal tubule is to secrete acid into the tubule lumen, thereby reabsorbing approximately 80% of the filtered HCO3- as well as generating new HCO3- for regulating blood pH. This review summarizes the cellular and molecular events that underlie four major processes in HCO3- reabsorption. The first is CO2 entry across the apical membrane, which in large part ...

BACKGROUND Many aquatic photosynthetic microorganisms possess an inorganic-carbon-concentrating mechanism that raises the CO2 concentration at the intracellular carboxylation sites, thus compensating for the relatively low affinity of the carboxylating enzyme for its substrate. In cyanobacteria, the concentrating mechanism involves the energy-dependent influx of inorganic carbon, the accumulati...

Carbonic anhydrase activity was characterized in freshly dissociated Müller cells of the salamander retina. Intracellular pH was monitored using ratio imaging of the indicator dye BCECF as extracellular PCO2 was varied. The extracellular solution was switched rapidly (141 ms rise time) from a HEPES buffered to a CO2-HCO3- buffered solution (both pH 7.4). Introduction of CO2-HCO3- produced a rap...

The purpose of the present study was to determine whether isohydric changes in HCO3 concentration and Pco 2directly affect apical Na-dependent Pi(Na-Pi) cotransport in OK cells (opossum kidney cell line). Cells were kept at either 44 mM NaHCO3/10% CO2, pH 7.4 (high-HCO3/CO2condition), or 22 mM NaHCO3/5% CO2, pH 7.4 (low-HCO3/CO2condition) (for 14-24 h). Incubation in lower HCO3/CO2concentration...

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]....

Turtles possess a significant postcapillary CO2 partial pressure (PCO2) disequilibrium between arterial blood and alveolar gas. There are several possible explanations for this blood disequilibrium including a slow rate of erythrocyte physiological anion shift (Cl-/HCO3- exchange) or inaccessibility of plasma HCO3- to red blood cell or pulmonary carbonic anhydrase. The present study characteriz...

CO2 fi xation is a potential technology for the realization of photocatalytic CO2 reduction and synthesis of organic compounds from CO2 as a starting material. Many studies of CO2 fi xation or utilization have investigated ultra-visible light induced photocatalysis on semiconductors such as titanium dioxide1), silicon carbide1) and strontium titanate2) in heterogenous aqueous media. Biological ...

Although carbon dioxide (CO2) is known to be essential for Streptococcus pneumoniae growth, it is poorly understood how this respiratory tract pathogen adapts to the large changes in environmental CO2 levels it encounters during transmission, host colonization, and disease. To identify the molecular mechanisms that facilitate pneumococcal growth under CO2-poor conditions, we generated a random ...

Several studies suggest the involvement of Na+ and HCO3- transport in the formation of cerebrospinal fluid. Two Na+-dependent HCO3- transporters were recently localized to the epithelial cells of the rat choroid plexus (NBCn1 and NCBE), and the mRNA for a third protein was also detected (NBCe2) (Praetorius J, Nejsum LN, and Nielsen S. Am J Physiol Cell Physiol 286: C601-C610, 2004). Our goal wa...

Energetic costs associated with ion and acid-base regulation in response to ocean acidification have been predicted to decrease the energy available to fish for basic life processes. However, the low cost of ion regulation (6-15% of standard metabolic rate) and inherent variation associated with whole-animal metabolic rate measurements have made it difficult to consistently demonstrate such a c...