Possible mechanisms for the linkage of membrane potentials to metabolism by electrogenic transport processes with special reference toAscaris muscle

1973 ◽  
Vol 4 (1-2) ◽  
pp. 201-209 ◽  
Author(s):  
P. C. Caldwell
Keyword(s):  
Special Reference ◽  
Membrane Potentials ◽  
Transport Processes ◽  
Electrogenic Transport

scholarly journals Basolateral transport of tetraethylammonium by a clone of LLC-PK1 cells.

1992 ◽  
Vol 2 (10) ◽  
pp. 1507-1515
Author(s):  
T D McKinney ◽  
M B Scheller ◽  
M Hosford ◽  
M E Lesniak ◽  
T S Haseley
Keyword(s):  
Organic Cation ◽  
Basolateral Membrane ◽  
Transport Processes ◽  
Proton Exchange ◽  
Metabolic Inhibitors ◽  
Organic Cations ◽  
Dependent Manner ◽  
Electrogenic Transport ◽  
The Media ◽  
Uptake Medium

In these studies, a clone of cells derived from the porcine renal epithelial line LLC-PK1 grown on porous filters was used to evaluate basolateral uptake of the organic cation tetraethylammonium (TEA). (3H) TEA (1 microM) entered cells in a saturable and time-dependent manner achieving a steady-state value at 2 to 2.5 h. Uptake was reduced by hypothermia and the metabolic inhibitors sodium azide and iodoacetate. Several other organic cations in 1 mM concentrations inhibited the majority of TEA uptake. In lower concentrations, the inhibitory potency of these was: verapamil greater than cimetidine approximately amiloride approximately quinidine greater than procainamide approximately N1-methylnicotinamide. When sodium was replaced with potassium in the uptake medium, TEA uptake was also reduced consistent with electrogenic transport. However, uptake was reduced further by 1 mM cimetidine in the presence of both NaCl and KCl buffers. TEA uptake was not significantly different when the media pH was varied from 6.0 to 8.0. In addition, results of experiments in which intracellular pH was altered with NH4Cl were not consistent with the presence of organic cation/proton exchange. TEA/TEA exchange could not be demonstrated in experiments in which cells were preloaded with 1 mM nonradioactive TEA and uptake of (3H)TEA was measured or in which nonradioactive TEA in the external medium failed to enhance efflux from cells preloaded with (3H)TEA. These results indicate that the basolateral membrane of LLC-PKc10 cells has one or more transport processes for the mediated uptake of organic cations. However, the precise mechanism(s) involved in this transport remains to be elucidated.

Studies on Locust Rectum: II. Identification of Specific Ion Transport Processes Regulated by Corpora Cardiaca and Cyclic-AMP

1980 ◽  
Vol 86 (1) ◽  
pp. 225-236
Author(s):  
J. H. SPRING ◽  
J. E. PHILLIPS
Keyword(s):  
Cyclic Amp ◽  
Ion Transport ◽  
Time Course ◽  
Transport Processes ◽  
Electrogenic Transport ◽  
Corpora Cardiaca ◽  
Before And After ◽  
Net Flux ◽  
Unidirectional Fluxes ◽  
Stimulation Of

Please send reprint requests to J. E. Phillips. 1. The unidirectional fluxes of 36Cl− and 22Na+ across short-circuited locust recta bathed in a simple NaCl saline were followed with time. Unidirectional fluxes and net flux of 22Na+ to the haemocoel side all remained constant for at least 4 h and were unaffected by either corpora cardiaca homogenate (CC) or cAMP. 2. Both CC and cAMP stimulated influx and net flux of 36Cl− to the haemocoel side. Over the whole time course of the experiment, i.e. both before and after stimulation, net Cl− flux approximately equalled the shortcircuit current (ISC). 3. Neither CC nor cAMP caused substantial stimulation of ISC or transepithelial electropotential difference (PD) if all Cl− in the bathing saline was replaced by either sulphate or nitrate or acetate. 4. Acetate saline sustains ISC, PD and transepithalial resistance (R) at higher levels than does simple Cl-saline. 5. Experiments with Cl-free, SO4-salines suggest that alternate electrogenic transport processes can be slowly turned on when Cl− is absent, provided a complex saline which contains several organic constituents, or simple acetate saline, is present.

Membrane Potentials in Carrot Root Cells

1977 ◽  
Vol 4 (2) ◽  
pp. 241 ◽  
Author(s):  
W.P Anderson ◽  
R.N Robertson ◽  
B.J Wright
Keyword(s):  
Membrane Potentials ◽  
Xylem Parenchyma ◽  
Carrot Root ◽  
Root Cells ◽  
Membrane Hyperpolarization ◽  
Electrogenic Transport ◽  
Carbonyl Cyanide ◽  
External Conditions ◽  
Complete Nutrient Solution ◽  
Single Exponential

Membrane potentials in carrot root xylem parenchyma cells, aged for at least 5 days after excision from the parent organ, were measured under a variety of external conditions by standard intracellular electrode methods. The respiration blocking agents cyanide and carbon monoxide (in the dark) produced large (up to 90 mV) depolarizations which could be described by single exponential decay curves having rate constants (or half-times) of 0.065 s-1 (t*1/2 = 10.8 s) and 0.094 s-1 (t*1/2 = 7.4 s) respectively. The uncoupler carbonyl cyanide m-chlorophenylhydrazone caused a single exponential membrane depolarization with a rate constant of 0.0054 s-1(t*1/2 = 126 s). These effects are thought to reflect the action of an active electrogenic H+ extrusion pump at the plasmalemma. A second, minor electrogenic transport, causing depolarization of about 10 mV in the restlng state, and due to an obligate electrogenic coupling to Cl- influx has been confirmed in KCl-pretreated tissue. In tissue pretreated in more complete nutrient solution, there is no evidence of a Cl- -coupled electrogenic exchange. This seems to be the first report of two independent electrogenic mechanisms operating in a plant cell and, interestingly, they act in opposite senses, the major H+ extrusion causing membrane hyperpolarization, the minor Cl- -influx-coupled exchange causing depolarization, in the normal resting cell.

Effects of Nitrogen Mustard-N-Oxide on Ionic Activities of Inner Ear Fluid and Ionic Permeabilities of the Cochlear Partition in the Guinea Pig

1989 ◽  
Vol 98 (5) ◽  
pp. 379-383 ◽  
Author(s):  
Katsuhisa Ikeda ◽  
Tomonori Takasaka ◽  
Jun Kusakari ◽  
Yoshitaka Saito
Keyword(s):  
Guinea Pig ◽  
Normal State ◽  
Permeability Coefficient ◽  
Nitrogen Mustard ◽  
Endocochlear Potential ◽  
Transport Processes ◽  
Scala Tympani ◽  
Electrogenic Transport ◽  
Ion Concentrations ◽  
Cochlear Partition

The effect of nitrogen mustard-N-oxide (NMO) on the endocochlear potential (EP) was investigated from the aspect of the ion concentrations and permeabilities in the cochlea. Compared with the untreated animals, in NMO-treated animals 20 to 30 hours after administration, the EP was decreased (30.8 ± 3.5 mV in NMO versus 82.4 ± 1.6 mV in control), the K+ concentration in perilymph of the scala tympani was increased (8.2 ± 1.0 m M versus 5.3 ± 0.7 m M), the K+ concentration in endolymph was decreased (128.5 ± 10.6 m M versus 157.9 ± 7.9 m M), and the Na+ concentration in endolymph was increased (9.6 ± 3.6 m M versus 2.5 ± 0.4 m M). The permeability coefficient for Na+ of the cochlear partition in the NMO-treated animals significantly decreased, while that for Cl− significantly increased. The negative EP, which presumably exists in the normal state, diminished further (−2.7 mV versus −27.8 mV), and the calculated electrogenic potential of the EP was depressed remarkably (33.5 mV versus 110.2 mV). The results suggest that the effects of NMO involved changes in ion permeabilities of the partition and the inhibition of electrogenic transport processes in the cochlea.

Physiology and Pathophysiology of Potassium Channels in Gastrointestinal Epithelia

2008 ◽  
Vol 88 (3) ◽  
pp. 1119-1182 ◽  
Author(s):  
Dirk Heitzmann ◽  
Richard Warth
Keyword(s):  
Gastrointestinal Tract ◽  
Epithelial Cells ◽  
Cell Volume Regulation ◽  
Transport Processes ◽  
Fine Tuning ◽  
Electrogenic Transport ◽  
Channel Function ◽  
Channel Expression ◽  
Important Barrier

Epithelial cells of the gastrointestinal tract are an important barrier between the “milieu interne” and the luminal content of the gut. They perform transport of nutrients, salts, and water, which is essential for the maintenance of body homeostasis. In these epithelia, a variety of K+ channels are expressed, allowing adaptation to different needs. This review provides an overview of the current literature that has led to a better understanding of the multifaceted function of gastrointestinal K+ channels, thereby shedding light on pathophysiological implications of impaired channel function. For instance, in gastric mucosa, K+ channel function is a prerequisite for acid secretion of parietal cells. In epithelial cells of small intestine, K+ channels provide the driving force for electrogenic transport processes across the plasma membrane, and they are involved in cell volume regulation. Fine tuning of salt and water transport and of K+ homeostasis occurs in colonic epithelia cells, where K+ channels are involved in secretory and reabsorptive processes. Furthermore, there is growing evidence for changes in epithelial K+ channel expression during cell proliferation, differentiation, apoptosis, and, under pathological conditions, carcinogenesis. In the future, integrative approaches using functional and postgenomic/proteomic techniques will help us to gain comprehensive insights into the role of K+ channels of the gastrointestinal tract.

Computational studies of ion-water flux coupling in the airway epithelium. I. Construction of model

1996 ◽  
Vol 270 (6) ◽  
pp. C1751-C1763 ◽  
Author(s):  
J. A. Novotny ◽  
E. Jakobsson
Keyword(s):  
Water Transport ◽  
Airway Epithelium ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Ionic Composition ◽  
Membrane Potentials ◽  
Transport Processes ◽  
Model Parameters ◽  
Constant Field ◽  
Sodium Potassium

A mathematical model of ion and water transport across the airway epithelium is presented. The model consists of 12 state variables representing ion concentrations, volumes, and membrane potentials. All osmotically significant membrane transport processes for which there is conclusive experimental evidence are included: passive apical sodium and chloride movement, basolateral sodium-potassium pumping, basolateral sodium-potassium-chloride cotransport, passive basolateral potassium movement, nonselective passive paracellular ion motion, and water transport across all membranes. Ion movements are described by Michaelis-Menten kinetics or by the constant field flux equation. Model parameters are established with Ussing chamber data. Model behavior is validated by comparing in vitro simulations with experimental results. The model accurately reproduces short-circuit chloride and sodium fluxes, short-circuit current, and open-circuit membrane potentials from Ussing chamber data in the secreting and nonsecreting states. The model is then used to describe the behavior of the airway epithelium in vivo, in which case the apical electrolyte compartment is small and of variable size and ionic composition.

Sign in / Sign up

Export Citation Format

Share Document