Ae4 (Slc4a9) belongs to the Slc4a family of Cl(-)/HCO3 (-) exchangers and Na(+)-HCO3 (-) cotransporters, but its ion transport cycle is poorly understood. In this study, we find that native Ae4 activity in mouse salivary gland acinar cells supports Na(+)-dependent Cl(-)/HCO3 (-) exchange that is comparable with that obtained upon heterologous expression of mouse Ae4 and human AE4 in CHO-K1 cell...

Net HCO3- transport in the rabbit kidney cortical collecting duct (CCD) is mediated by simultaneous H+ secretion and HCO3- secretion, most likely occurring in a alpha- and beta-intercalated cells (ICs), respectively. The polarity of net HCO3- transport is shifted from secretion to absorption after metabolic acidosis or acid incubation of the CCD. We investigated this adaptation by measuring net...

Intestinal HCO3- secretion is essential to marine teleost fish osmoregulation and comprises a considerable source of base efflux attributable to both serosal HCO3- and endogenous CO2 hydration. The role of intestinal HCO3- secretion in dynamic acid-base balance regulation appears negligible in studies of unfed fish, but evidence of high intestinal fluid [HCO3-] in fed marine teleosts led us to ...

Atrial natriuretic peptide (ANP) is known to influence NaCl transport in the medullary thick ascending limbs (MAL), where the largest NaCl reabsorption occurs among distal nephron segments in response to arginine vasopressin (AVP). In the present study, we investigated the effect of ANP on bicarbonate (HCO3 (-)) transport in the MAL using an isolated tubule perfusion technique. The HCO3 (-) con...

HCO3- secretion by gastric mucous cells is essential for protection against acidic injury and peptic ulcer. Herein we report the identification of an apical HCO3- transporter in gastric surface epithelial cells. Northern hybridization and RT-PCR demonstrate the expression of this transporter, also known as SLC26A9, in mouse and rat stomach and trachea (but not kidney). In situ hybridization in ...

Bicarbonate (HCO3(-)) is essential for preimplantation embryo development. However, the mechanism underlying the HCO3(-) transport into the embryo remains elusive. In the present study, we examined the possible involvement of Cl(-)/HCO3(-) exchanger in mediating HCO3(-) transport into the embryo. Our results showed that depletion of extracellular Cl(-), even in the presence of HCO3(-), suppress...

Cyclic AMP stimulates HCO3 secretion and Cl self-exchange in rabbit cortical collecting tubule. We found that varying peritubular [Cl] changed the Cl self-exchange rate with saturation kinetics (Km, 3-4 mM). HCO3 secretion also showed saturation kinetics as a function of mean luminal [Cl] (Km, 4-11 mM). Both Cl self-exchange and Cl-HCO3 exchange thus appear to be carrier-mediated. Addition/remo...

At 5 degree C addition of CO2 or HCO3- to CO (HCO3-)-depleted thylakoids (containing 100 mM formate) initiates, within 10 s, the activation of the Hill reaction in light. In contrast to HCO3- addition, where there is a lag of 6-8 s, the activation by CO2 addition is almost instantaneous. With CO2, prior addition of carbonic anhydrase produces a lag of about 6 s that approaches the lag observed ...

Serotonin (5-HT) and other contractile agonists stimulate Na(+)-H+ exchange in vascular smooth muscle. Since intracellular alkalinization, per se, stimulates contraction, we tested whether 5-HT-induced contraction was associated with an increased pHi. In HCO3(-)-free buffer (pHo 7.4), 5-HT (10(-5) M) increased pHi, as measured by 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein fluorescence, f...

BACKGROUND Buffering to achieve pH control is crucial for successful trichloroethene (TCE) anaerobic bioremediation. Bicarbonate (HCO3-) is the natural buffer in groundwater and the buffer of choice in the laboratory and at contaminated sites undergoing biological treatment with organohalide respiring microorganisms. However, HCO3- also serves as the electron acceptor for hydrogenotrophic metha...