Intracellular pH (pHi) in squid giant axons recovers from acid loads by means of a Na(+)-dependent Cl-HCO3 exchanger, the actual mechanism of which might be exchange of: (i) external Na+ and HCO3- for internal Cl- and H+, (ii) Na+ plus two HCO3- for Cl-, (iii) Na+ and CO3= for Cl-, or (iv) the NaCO3- ion pair for Cl-. Here we examine sensitivity of transport to changes of extracellular pH (pHo)...

Hypercapnia is clinically defined as an arterial blood partial pressure of CO2 of above 40 mmHg and is a feature of chronic lung disease. In previous studies we have demonstrated that hypercapnia modulates agonist-stimulated cAMP levels through effects on transmembrane adenylyl cyclase activity. In the airways, cAMP is known to regulate cystic fibrosis transmembrane conductance regulator (CFTR)...

Neurosensory and behavioural disruptions are some of the most consistently reported responses upon exposure to ocean acidification-relevant CO2 levels, especially in coral reef fishes. The underlying cause of these disruptions is thought to be altered current across the GABAA receptor in neuronal cells due to changes in ion gradients (HCO3(-) and/or Cl(-)) that occur in the body following compe...

P microorganisms can acclimate to a wide range of CO2 concentration, from as low as 0.001% to '10% CO2 (volyvol in the air in equilibrium with their environment). Some can even grow in the presence of 40% CO2 (1). Acclimation to a limiting CO2 level, well below the Km(CO2) of their carboxylating enzyme, Rubisco (ribulose 1,5-bisphosphate carboxylaseyoxygenase), is achieved by substantial physio...

Lidocaine has been reported to be more depressant in ischemic than normal myocardium. To determine the influence of pH on the electrophysiological effects of lidocaine, we recorded transmembrane potential and dV/dtmul from guinea pig papillary muscles mounted in a single sucrose gap. Recovery kinetics of dV/dtma, were studied by introducing progressively early premature responses during phase 4...

Lidocaine has been reported to be more depressant in ischemic than normal myocardium. To determine the influence of pH on the electrophysiological effects of lidocaine, we recorded transmembrane potential and dV/dtmul from guinea pig papillary muscles mounted in a single sucrose gap. Recovery kinetics of dV/dtma, were studied by introducing progressively early premature responses during phase 4...

Carbon monoxide dehydrogenase of anaerobic bacteria catalyzes the reversible conversion of CO to "CO2". With the enzyme from Peptostreptococcus productus it is shown that CO2 rather than HCO3- (H2CO3) is the active species of "CO2" formed by this dehydrogenase.

The supply of inorganic carbon (Ci; CO2 and HCO3 (-)) is an environmental rate-limiting factor in aquatic photosynthetic organisms. To overcome the difficulty in acquiring Ci in limiting-CO2 conditions, an active Ci uptake system called the CO2-concentrating mechanism (CCM) is induced to increase CO2 concentrations in the chloroplast stroma. An ATP-binding cassette transporter, HLA3, and a form...

The Slr1991 adenylyl cyclase of the model prokaroyte Synechocystis PCC 6803 was stimulated 2-fold at 20 mM total C(i) (inorganic carbon) at pH 7.5 through an increase in k(cat). A dose response demonstrated an EC50 of 52.7 mM total C(i) at pH 6.5. Slr1991 adenylyl cyclase was activated by CO2, but not by HCO3-. CO2 regulation of adenylyl cyclase was conserved in the CyaB1 adenylyl cyclase of An...

We investigated in a physiological salt solution (PSS) containing HCO3- the intracellular pH (pHi) regulating mechanisms in smooth muscle cells cultured from human internal mammary arteries, using the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) and 22Na+ influx rates. The recovery of pHi from an equivalent intracellular acidosis was more rapid when the cells were ...