Ion Transport by Turtle Colon: A Role for Volume-Sensing Transporters in the Basolateral Membrane

1993 ◽  
pp. 49-66
Author(s):  
David C. Dawson ◽  
Marc A. Post
Keyword(s):  
Ion Transport ◽  
Basolateral Membrane

Succinate alters respiration, membrane potential, and intracellular K+ in proximal tubule

1988 ◽  
Vol 255 (6) ◽  
pp. F1170-F1177 ◽  
Author(s):  
S. R. Gullans ◽  
B. C. Kone ◽  
M. J. Avison ◽  
G. Giebisch
Keyword(s):  
Membrane Potential ◽  
Atpase Activity ◽  
Ion Transport ◽  
Proximal Tubule ◽  
Basolateral Membrane ◽  
Coupling Efficiency ◽  
Atp Synthesis ◽  
Dependent Manner ◽  
Kinetic Evaluation ◽  
Apparent Increase

Succinate, a dicarboxylic acid, is an intermediate in the Krebs cycle that is transported and metabolized by the renal proximal tubule. It is also known to increase proximal tubule transport of phosphate and glucose but not fluid by unknown mechanisms. In the present study, succinate increased proximal tubule respiration in a dose-dependent manner, and a kinetic evaluation indicated that two separate processes were activated. A lower-affinity (Km = 0.9 mM), higher-capacity stimulation (Vmax increase of 49%) was attributed to a decrease in the mitochondrial coupling efficiency. A higher-affinity process (Km = 0.012 mM) was related to an apparent increase in ATP synthesis. The apparent increase in ATP synthesis was not associated with a change in Na+-K+-ATPase activity, however, but rather indicated a 49% increase in ion transport-independent ATP utilization. Basolateral membrane potential hyperpolarized by -7 mV in the presence of succinate, and this was related to an increase in the K+ transference number. Finally, 1 and 5 mM succinate promoted a net cellular uptake of K+, leading to an 11% increase in intracellular K+, which was not the result of an increase in Na+-K+-ATPase activity. Thus the cellular entry and metabolism of succinate promotes multiple changes in ion transport without altering Na+-K+-ATPase activity.

Comparison of ion transport by cultured secretory and absorptive canine airway epithelia

1988 ◽  
Vol 254 (4) ◽  
pp. C535-C547 ◽  
Author(s):  
R. C. Boucher ◽  
E. H. Larsen
Keyword(s):  
Cell Culture ◽  
Ion Transport ◽  
Primary Cell Culture ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Culture Technique ◽  
Primary Cell ◽  
Airway Epithelia ◽  
Cell Culture Techniques ◽  
Native Tissue

The use of primary cell culture techniques to predict the function of native respiratory epithelia was tested in studies of dog airway epithelia. Epithelial cells from Cl- secretory (tracheal) and Na+ absorptive (bronchial) airway regions were isolated by enzymatic digestion, plated on collagen matrices, and maintained in serum-free, hormone-supplemented media. Transepithelial and intracellular studies showed that both the tracheal and bronchial culture preparations exhibited bioelectric parameters quantitatively similar to those of intact tissues. Similar to the native tissue, the tracheal preparation exhibited an equivalent short-circuit circuit (Ieq) that was sensitive to inhibitors of Cl- transport (bumetanide, diphenylamine carboxylic acid) but was insensitive to an inhibitor of Na+ transport, amiloride. In contrast, the bronchial preparation, like the native tissue, exhibited an Ieq sensitive to amiloride but insensitive to bumetanide. As compared with the trachea, the bronchial (absorptive) epithelium is characterized by 1) a large amiloride-sensitive cellular conductance and 2) a relatively depolarized basolateral membrane. We conclude that this primary cell culture technique provides epithelial preparations comparable to the native tissue and suitable for quantitative studies of regional differences in ion transport function.

scholarly journals Interleukin-17A induces bicarbonate secretion in normal human bronchial epithelial cells

2009 ◽  
Vol 296 (2) ◽  
pp. L257-L266 ◽  
Author(s):  
James L. Kreindler ◽  
Carol A. Bertrand ◽  
Robert J. Lee ◽  
Thomas Karasic ◽  
Shean Aujla ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Ion Transport ◽  
Antimicrobial Peptide ◽  
Basolateral Membrane ◽  
Chloride Secretion ◽  
Bicarbonate Secretion ◽  
Immune Functions ◽  
Bronchial Epithelial ◽  
Interleukin 17A ◽  
Well Differentiated

The innate immune functions of human airways include mucociliary clearance and antimicrobial peptide activity. Both functions may be affected by changes in epithelial ion transport. Interleukin-17A (IL-17A), which has a receptor at the basolateral membrane of airway epithelia, is a T cell cytokine that has been shown to increase mucus secretion and antimicrobial peptide production by human bronchial epithelial (HBE) cells. Furthermore, IL-17A levels are increased in sputum from patients during pulmonary exacerbations of cystic fibrosis. Therefore, we investigated the effects of IL-17A on basal, amiloride-sensitive, and forskolin-stimulated ion transport in mature, well-differentiated HBE cells. Exposure of HBE monolayers to IL-17A for 48 h induced a novel forskolin-stimulated bicarbonate secretion in addition to forskolin-stimulated chloride secretion and resulted in alkalinization of liquid on the mucosal surface of polarized cells. IL-17A-induced bicarbonate secretion was cystic fibrosis transmembrane conductance regulator (CFTR)-dependent, mucosal chloride-dependent, partially Na+-dependent, and sensitive to serosal, but not mucosal, stilbene inhibition. These data suggest that IL-17A modulates epithelial bicarbonate secretion and implicate a mechanism by which airway surface liquid pH changes may be abnormal in cystic fibrosis.

Interrelationships of ion transport in rat submaxillary duct epithelium

1982 ◽  
Vol 242 (2) ◽  
pp. F132-F139 ◽  
Author(s):  
H. Knauf ◽  
R. Lubcke ◽  
W. Kreutz ◽  
G. Sachs
Keyword(s):  
Ion Transport ◽  
Basolateral Membrane ◽  
Ion Concentration ◽  
Transport Systems ◽  
Salivary Duct ◽  
Basolateral Membranes ◽  
A Value ◽  
Duct Epithelium ◽  
K Secretion

The transport of Na+, K+, Cl-, and HCO3(-) across the epithelium of the rat submaxillary salivary duct is postulated to be due to the coupling of the basolateral Na+-K+-ATPase with various ion transport systems in the luminal and basolateral membranes. Na+ reabsorption depends on the presence of a rheogenic (Na+ conductance) and an electroneutral (Na+:H exchange) pathway, both of which are sensitive to amiloride. K+ secretion is postulated to be mediated by a K+: H+ antiport, coupling between Na+ reabsorption and K+ secretion, thus depending on local H+ ion concentration. The ratio between electroneutral Na+ influx and K+ efflux, therefore, determines the rate of HCO3(-) secretion. In the absence of Na+ influx, although K+ efflux falls, HCO3(-) secretion rises to a value equal to that of K+ secretion. The maintenance of K+ secretion in the absence of luminal Na+ requires an additional Na+-entry step across the basolateral membrane, also postulated to be due to Na+:H+ exchange.

scholarly journals Distinct Apical and Basolateral Membrane Requirements for Stretch-induced Membrane Traffic at the Apical Surface of Bladder Umbrella Cells

2009 ◽  
Vol 20 (1) ◽  
pp. 282-295 ◽  
Author(s):  
Weiqun Yu ◽  
Puneet Khandelwal ◽  
Gerard Apodaca
Keyword(s):  
Ion Transport ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Dynamics ◽  
Apical Surface ◽  
Membrane Domains ◽  
Mechanical Stimuli ◽  
Membrane Tension ◽  
Subsequent Increase ◽  
Umbrella Cells

Epithelial cells respond to mechanical stimuli by increasing exocytosis, endocytosis, and ion transport, but how these processes are initiated and coordinated and the mechanotransduction pathways involved are not well understood. We observed that in response to a dynamic mechanical environment, increased apical membrane tension, but not pressure, stimulated apical membrane exocytosis and ion transport in bladder umbrella cells. The exocytic response was independent of temperature but required the cytoskeleton and the activity of a nonselective cation channel and the epithelial sodium channel. The subsequent increase in basolateral membrane tension had the opposite effect and triggered the compensatory endocytosis of added apical membrane, which was modulated by opening of basolateral K+ channels. Our results indicate that during the dynamic processes of bladder filling and voiding apical membrane dynamics depend on sequential and coordinated mechanotransduction events at both membrane domains of the umbrella cell.

Turtle urinary bladder: regulation of ion transport by dynamic changes in plasma membrane area

1989 ◽  
Vol 257 (5) ◽  
pp. R973-R981
Author(s):  
D. L. Stetson
Keyword(s):  
Urinary Bladder ◽  
Ion Transport ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Transport Processes ◽  
Granular Cells ◽  
Membrane Area ◽  
Low Co2 ◽  
In Series ◽  
Cl Channels

Turtle urinary bladder possesses four ion transport processes: Na+ absorption, H+ secretion, and HCO3- secretion-Cl- absorption. Each transport process is performed by a specific epithelial cell type. Granular cells absorb Na+ but they are not sensitive to antidiuretic hormone (ADH), unlike toad bladder granular cells. alpha-Carbonic anhydrase-rich (CA) cells secrete H+ via an apical H+-adenosinetriphosphatase (ATPase). Under conditions of low CO2 tension, this active pump is contained in the limiting membranes of certain cytoplasmic vesicles. The vesicles fuse with the apical membrane, and H+ pumps are incorporated into that membrane, as physiological conditions demand increased H+ secretion. The stimulus for fusion of these vesicles with the apical membrane appears to be intracellular acidification. beta-CA cells secrete HCO3- and reabsorb Cl-, both processes driven by H+-ATPase in the basolateral membrane in series with an apical Cl- -HCO3- exchanger. Increased intracellular adenosine 3',5'-cyclic monophosphate concentration in beta-cells stimulates net HCO3- secretion and induces an electrogenic component of this flux by activating an apical Cl- channel. This activation accompanies the fusion of an intracellular tubulovesicular network with the apical membrane. The membrane of this network may contain Cl- channels.

Immunolocalization of ion-transport proteins to branchial epithelium mitochondria-rich cells in the mudskipper (Periophthalmodon schlosseri)

2000 ◽  
Vol 203 (15) ◽  
pp. 2297-2310 ◽  
Author(s):  
J.M. Wilson ◽  
D.J. Randall ◽  
M. Donowitz ◽  
A.W. Vogl ◽  
A.K. Ip
Keyword(s):  
Boundary Layer ◽  
Carbonic Anhydrase ◽  
Ion Transport ◽  
Basolateral Membrane ◽  
Anion Channel ◽  
Carbonic Anhydrase Activity ◽  
Transport Proteins ◽  
Ph Effects ◽  
Periophthalmodon Schlosseri ◽  
Branchial Epithelium

The branchial epithelium of the mudskipper Periophthalmodon schlosseri is densely packed with mitochondria-rich (MR) cells. This species of mudskipper is also able to eliminate ammonia against large inward gradients and to tolerate extremely high environmental ammonia concentrations. To test whether these branchial MR cells are the sites of active ammonia elimination, we used an immunological approach to localize ion-transport proteins that have been shown pharmacologically to be involved in the elimination of NH(4)(+) (Na(+)/NH(4)(+) exchanger and Na(+)/NH(4)(+)-ATPase). We also investigated the role of carbonic anhydrase and boundary-layer pH effects in ammonia elimination by using the carbonic anhydrase inhibitor acetazolamide and by buffering the bath water with Hepes, respectively. In the branchial epithelium, Na(+)/H(+) exchangers (both NHE2- and NHE3-like isoforms), a cystic fibrosis transmembrane regulator (CFTR)-like anion channel, a vacuolar-type H(+)-ATPase (V-ATPase) and carbonic anhydrase immunoreactivity are associated with the apical crypt region of MR cells. Associated with the MR cell basolateral membrane and tubular system are the Na(+)/K(+)-ATPase and a Na(+)/K(+)/2Cl(−) cotransporter. A proportion of the ammonia eliminated by P. schlosseri involves carbonic anhydrase activity and is not dependent on boundary-layer pH effects. The apical CFTR-like anion channel may be serving as a HCO(3)(−) channel accounting for the acid-base neutral effects observed with net ammonia efflux inhibition.

scholarly journals Cyclic AMP modulation of ion transport across frog retinal pigment epithelium. Measurements in the short-circuit state.

1984 ◽  
Vol 83 (6) ◽  
pp. 853-874 ◽  
Author(s):  
S Miller ◽  
D Farber
Keyword(s):  
Retinal Pigment Epithelium ◽  
Cyclic Amp ◽  
Ion Transport ◽  
Apical Membrane ◽  
Short Circuit ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Basolateral Membrane ◽  
Active Absorption ◽  
Apical Side

In the frog retinal pigment epithelium (RPE), the cellular levels of cyclic AMP (cAMP) were measured in control conditions and after treatment with substances that are known to inhibit phosphodiesterase (PDE) activity (isobutyl-1-methylxanthine, SQ65442) or stimulate adenylate cyclase activity (forskolin). The cAMP levels were elevated by a factor of 5-7 compared with the controls in PDE-treated tissues and by a factor of 18 in forskolin-treated tissues. The exogenous application of cAMP (1 mM), PDE inhibitors (0.5 mM), or forskolin (0.1 mM) all produced similar changes in epithelial electrical parameters, such as transepithelial potential (TEP) and resistance (Rt), as well as changes in active ion transport. Adding 1 mM cAMP to the solution bathing the apical membrane transiently increased the short-circuit current (SCC) and the TEP (apical side positive) and decreased Rt. Microelectrode experiments showed that the elevation in TEP is due mainly to a depolarization of the basal membrane followed by, and perhaps also accompanied by, a smaller hyperpolarization of the apical membrane. The ratio of the apical to the basolateral membrane resistance increased in the presence of cAMP, and this increase, coupled with the decrease in Rt and the basolateral membrane depolarization, is consistent with a conductance increase at the basolateral membrane. Radioactive tracer experiments showed that cAMP increased the active secretion of Na (choroid to retina) and the active absorption of K (retina to choroid). Cyclic AMP also abolished the active absorption of Cl across the RPE. In sum, elevated cellular levels of cAMP affect active and passive transport mechanisms at the apical and basolateral membranes of the bullfrog RPE.

scholarly journals The Drosophila NKCC Ncc69 is required for normal renal tubule function

2012 ◽  
Vol 303 (8) ◽  
pp. C883-C894 ◽  
Author(s):  
Aylin R. Rodan ◽  
Michel Baum ◽  
Chou-Long Huang
Keyword(s):  
Ion Transport ◽  
Renal Tubule ◽  
Basolateral Membrane ◽  
Malpighian Tubule ◽  
Transport Processes ◽  
Wild Type ◽  
Atpase Inhibitor ◽  
Transport Pathways ◽  
Epithelial Ion Transport

Epithelial ion transport is essential to renal homeostatic function, and it is dysregulated in several diseases, such as hypertension. An understanding of the insect renal (Malpighian) tubule yields insights into conserved epithelial ion transport processes in higher organisms and also has implications for the control of insect infectious disease vectors. Here, we examine the role of the Na+-K+-2Cl− (NKCC) cotransporter Ncc69 in Drosophila tubule function. Ncc69 mutant tubules have decreased rates of fluid secretion and K+ flux, and these phenotypes were rescued by expression of wild-type Ncc69 in the principal cells of the tubule. Na+ flux was unaltered in Ncc69 mutants, suggesting Na+ recycling across the basolateral membrane. In unstimulated tubules, the principal role of the Na+-K+-ATPase is to generate a favorable electrochemical gradient for Ncc69 activity: while the Na+-K+-ATPase inhibitor ouabain decreased K+ flux in wild-type tubules, it had no effect in Ncc69 mutant tubules. However, in the presence of cAMP, which stimulates diuresis, additional Na+-K+-ATPase-dependent K+ transport pathways are recruited. In studying the effects of capa-1 on wild-type and Ncc69 mutant tubules, we found a novel antidiuretic role for this hormone that is dependent on intact Ncc69, as it was abolished in Ncc69 mutant tubules. Thus, Ncc69 plays an important role in transepithelial ion and fluid transport in the fly renal tubule and is a target for regulation in antidiuretic states.

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