scholarly journals Some Kinetic and Metabolic Characteristics of Calcium-Induced Potassium Transport in Human Red Cells

1972 ◽  
Vol 60 (4) ◽  
pp. 406-429 ◽  
Author(s):  
Floyd M. Kregenow ◽  
Joseph F. Hoffman
Keyword(s):  
Flux Ratio ◽  
Iodoacetic Acid ◽  
Cell System ◽  
Na Transport ◽  
Metabolic Characteristics ◽  
Substrate Removal ◽  
Maximum Value ◽  
Metabolic Dependence ◽  
K Permeability ◽  
Human Red Cells

When fresh human erythrocytes or their ghosts are incubated with Ca + IAA (iodoacetic acid) + adenosine, K permeability increases; K permeability also increases when energy-depleted cells or their ghosts are incubated with Ca alone. Na transport decreases or remains unaltered in both situations. The Ca-induced increase in K permeability in the depleted cell system is qualitatively similar to that seen in the fresh cell system and furnishes a means for studying the metabolic dependence of calcium's action. Studies with the depleted system suggest that the normal refractiveness of the cell to calcium is provided by a metabolically dependent substrate. Removal of this substrate allows Ca to enter the cell and exert its effect. By using 47Ca, a maximum value was obtained (3–7 x 10-6 moles/liter of red blood cells) for the quantity of calcium that is taken up by the cell and responsible for the change in K permeability. Measurements of the unidirectional fluxes of K, obtained during the time Ca increases K permeability, appear to satisfy the flux ratio equation for passive diffusion through a membrane.

Role of metabolism in K-induced tension changes in guinea pig taenia coli

1965 ◽  
Vol 208 (6) ◽  
pp. 1203-1205 ◽  
Author(s):  
M. Pfaffman ◽  
N. Urakawa ◽  
W. C. Holland
Keyword(s):  
Guinea Pig ◽  
Active Transport ◽  
Underlying Mechanism ◽  
Taenia Coli ◽  
Na Transport ◽  
Phasic Response ◽  
Metabolic Intermediates ◽  
Substrate Removal ◽  
Insight Into

Further insight into the underlying mechanism(s) of the K-induced phasic and tonic contractions of the taenia coli of the guinea pig was obtained by examining the effects of various metabolic intermediates, inhibitors of metabolism and active transport, on these responses. Evidence is presented to support the thesis that the tonic response is dependent on the aerobic breakdown of carbohydrates and is abolished by substrate removal, a decrease of temperature, DNP, lithium, and ouabain. These same factors have little or no effect on the phasic response. From the evidence presented, it is concluded that the phasic response is a passive process, whereas the tonic contracture is an active one depending on metabolism and possibly linked to active Na transport.

Na+-K+ pump stoichiometry and basolateral membrane permeability of frog corneal epithelium

1986 ◽  
Vol 250 (5) ◽  
pp. F850-F859 ◽  
Author(s):  
O. A. Candia ◽  
P. Cook
Keyword(s):  
Membrane Permeability ◽  
Amphotericin B ◽  
Corneal Epithelium ◽  
Flow Condition ◽  
Basolateral Membrane ◽  
Flux Ratio ◽  
Na Currents ◽  
Static Head ◽  
K Permeability ◽  
Variable Stoichiometry

The Na+-K+ pump flux ratio and the Na+ and K+ permeability of the basolateral membrane of the isolated frog corneal epithelium were studied with the aid of microelectrodes by analyzing the effects of ouabain, Ba2+, and amphotericin B. The experiments were done in Cl(-)-free solutions, a situation that approximates that of static head. Ouabain produced a quick depolarization of the potential difference across the basolateral membrane (PDb) from -72 to -62 mV without a change in resistance. Ba2+ (3 mM) rapidly lowered PDb from -74 to -57 mV and decreased the apical-to-basolateral resistance ratio. The effects of ouabain and Ba2+ were additive. The Na+-K+ flux ratio at the pump was calculated to be 1.78, substantially less than when the tissue is in a level flow condition, suggesting a variable stoichiometry. The K+ and Na+ resistances of the basolateral membrane were 15.7 and 5.5 k omega X cm2, respectively, allowing K+ and Na+ currents that approximately matched those produced by the Na+-K+ pump. The resistance of the basolateral membrane (4.0 k omega X cm2) was double that reported in Cl(-)-rich solutions, suggesting that Cl- contributes to the conductance of this membrane.

scholarly journals p52PAI-1 gene expression in butyrate-induced flat revertants of v-ras-transformed rat kidney cells: mechanism of induction and involvement in the morphological response

1997 ◽  
Vol 321 (2) ◽  
pp. 431-437 ◽  
Author(s):  
Paul J. HIGGINS ◽  
Michael P. RYAN ◽  
Dawn M. JELLEY
Keyword(s):  
Transcriptional Activation ◽  
Rat Kidney ◽  
Molecular Genetic ◽  
Focal Adhesions ◽  
Fold Increase ◽  
Cell System ◽  
Early Gene ◽  
Cdna Insert ◽  
Morphological Response ◽  
Metabolic Characteristics

Sodium n-butyrate-induced flat reversion in v-K-rasoncogene-transformed rat kidney (KNRK) cells is associated with transcriptional activation of the p52PAI-1 gene (which encodes the type-1 inhibitor of plasminogen activator). Butyrate-initiated expression of p52PAI-1 mRNA and protein correlated with induced cell spreading and preceded development of cell-to-substrate focal adhesions. Such undersurface matrix contact structures, which are absent from parental KNRK cells, require proximal PAI-1 deposition for their stabilization. Stimulated p52PAI-1 expression by flat revertants (approximating 25-fold that of control cells) and the accompanying cytoarchitectural reorganization appeared to be programmed responses to butyrate as both events required de novoRNA and protein synthesis, metabolic characteristics consistent with a secondary pathway of gene regulation. To assess the relevance of p52PAI-1 induction to the process of flat reversion more critically, a molecular genetic approach was designed to maintain high-level constitutive p52PAI-1 synthesis in the absence of butyrate. KNRK cells transfected with a Rc/CMVPAI plasmid construct, in which expression of a p52PAI-1 cDNA insert was driven by enhancerŐpromoter sequences from the immediate-early gene of human cytomegalovirus, formed colonies comprised of flat-revertant-like cells with a greater frequency than did cells transfected with the Rc/CMV vector alone (24.8% and 1.7% respectively). Comparative analysis of randomly selected Rc/CMVPAI clones indicated that a 10-fold increase in immunoreactive p52PAI-1 protein, relative to Rc/CMV isolates, correlated with generation of the flat phenotype. These data suggest that induced p52PAI-1 expression probably functions in the development of morphological revertants in the KNRK cell system.

scholarly journals K Permeability of Nitella clavata in the Depolarized State

1973 ◽  
Vol 62 (5) ◽  
pp. 535-549 ◽  
Author(s):  
Hiroshi Kitasato
Keyword(s):  
Membrane Potential ◽  
Finite Number ◽  
Potassium Conductance ◽  
Membrane Potentials ◽  
Membrane Current ◽  
Half Maximum ◽  
Membrane Potential Change ◽  
Potassium Permeability ◽  
Maximum Value ◽  
K Permeability

Membrane current responses to sudden potential changes were recorded in solutions of various [K]o on 52 internodal cells of Nitella clavata. The membrane current after sudden depolarization had a component sensitive to [K]o which increased with time from 0.3 to 2.0 s and remained steady thereafter. This late current became zero at values of E and [K]o which suggests that the current was nearly all carried by K+. The potassium conductivity represented by this current increased with depolarization, with a half-maximum value at about -70 mV, and saturation at about -30 to -20 mV. The potassium conductance also increased with increasing [K]o, but less rapidly than predicted for constant potassium permeability. This failure of the conductance to increase with [K]o was relatively the same at all membrane potentials and may be explained by a model with a finite number of channels. No attempt was made to model the dependence of gK on time after depolarization or on membrane potential. However, the finding that the membrane potential did not affect the way in which the permeability depended on [K]o suggests that the membrane potential change does not affect the affinity of the sites, and that the increase in gK with time after depolarization is brought about by an increase in the number of channels with such sites.

Epithelial transport parameters: an analysis of experimental strategies

1983 ◽  
Vol 218 (1212) ◽  
pp. 309-329 ◽  
Keyword(s):  
Experimental Data ◽  
Epithelial Transport ◽  
Flux Ratio ◽  
Model Parameters ◽  
Acta Physiol ◽  
Transport Parameters ◽  
Na Transport ◽  
Experimental Conditions ◽  
System Parameters ◽  
Experimental Strategies

A set of experiments was simulated on a computer version of the Koefoed-Johnsen & Ussing model for high-resistance epithelia. The results obtained were analysed according to procedures commonly applied to the analyses of experimental data and interpreted in terms of the model parameters. Although the computer model encodes a stoichiometry of 3:2 for Na-K exchange through the Na pump, the simulation of published experimental procedures yields different figures in almost every case. We show that E Na as originally defined by Ussing & Zerahn ( Acta physiol. scand . 23, 110-127 (1951)) and as obtained from flux-ratio experiments has different values under different experimental conditions with unchanged system parameters and that it is distinct from E Na measured by other methods. We also show that unless the pump is saturated with internal Na an increase in the rate of pumping cannot cause a substantial increase in the rate of transepithelial Na transport.

In vitro studies of sodium transport across the lower intestine of a desert parrot

1980 ◽  
Vol 239 (3) ◽  
pp. R285-R290
Author(s):  
E. Skadhauge ◽  
T. J. Dawson
Keyword(s):  
Short Circuit ◽  
Electrical Potential ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Electrical Potential Difference ◽  
Na Transport ◽  
Salt Loading ◽  
Ussing Chambers ◽  
Lower Intestine

The lower intestine (coprodeum and colon) of the Australian parrot, the galah, was mounted in Ussing chambers. Short-circuit current (SCC), electrical potential difference (PD), and unidirectional fluxes of Na and Cl were measured in birds that were fed mixed seeds or were NaCl loaded. The net Na transport of both coprodeum and colon was nearly equal to the SCC, and the flux ratio for Cl was unity. In birds which received mixed seeds, average coprodeal Na transport was 7.8 mu eq . cm-2 . h-1, and PD was 19 mV. The Km for Na was 5.7 meq/l. In colon, Na transport was reduced by 67% and PD by 70%. The ratio between unidirectional Na and Cl fluxes in the serosa-mucosa direction was 0.7. Salt loading suppressed coprodeal, but increased colonic Na transport. The coprodeal and colonic SCC and NA transport of birds receiving mixed seeds were inhibited by amiloride on the mucosal side. Colonic SCC of NaCl-loaded birds was only slightly reduced by amiloride (by 17%), but stimulated by amino acids (by 18%).

Patterns of K+ permeation following inhibition of Na+ transport in rabbit cortical collecting tubule

1986 ◽  
Vol 250 (1) ◽  
pp. F120-F126 ◽  
Author(s):  
J. B. Stokes
Keyword(s):  
Apical Membrane ◽  
Na Transport ◽  
Transcellular Pathway ◽  
Collecting Tubule ◽  
Before And After ◽  
K Secretion ◽  
Pg E2 ◽  
Collecting Tubules ◽  
K Permeability ◽  
Cortical Collecting Tubule

The passive (lumen-to-bath) K+ permeation (KK) of rabbit cortical collecting tubules was measured before and after inhibition of Na+ transport. Inhibition of the Na-K pump with ouabain reduced KK. This result contrasts sharply with the previously described increase in KK observed following inhibition of Na+ transport with amiloride. These opposite changes in KK are owing to the fact that a substantial component of the lumen-to-bath K+ permeation involves a transcellular pathway. Amiloride, because it hyperpolarizes the apical membrane, increases KK; ouabain, because it depolarizes the cell, decreases KK. Previous results have also suggested that the cell K+ permeability is secondarily altered by these agents so that the changes in voltage and permeability are additive. These patterns of changes in KK were used to evaluate the mechanism of action of two agents that partially inhibit Na+ transport: vasopressin and prostaglandin (PG) E2. Their effect on KK was qualitatively similar to that of amiloride. In amiloride-treated tubules, neither vasopressin nor PGE2 altered KK. Neither did they alter the normal reduction in KK caused by pump inhibition. Thus they did not have any direct effect on K+ permeability. These results are consistent with the thesis that vasopressin and PGE2 inhibit Na+ absorption by reducing apical membrane permeability. The relation between the regulation of Na+ absorption and K+ permeation may have important implications for the regulation of K+ secretion by the cortical collecting tubule.

Active Transport of Potassium and Oxygen Consumption in the Isolated Midgut of Hyalophora Cecropia

1967 ◽  
Vol 46 (2) ◽  
pp. 235-248
Author(s):  
W. R. HARVEY ◽  
J. A. HASKELL ◽  
K. ZERAHN
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Active Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Na Transport ◽  
Maximum Value ◽  
Flux Measurements ◽  
Hyalophora Cecropia ◽  
K Transport

1. Flux measurements with 42K reveal that in the isolated midgut of Hyalophora cecropia 90 to 100 % of the short-circuit current is carried by the active transport of potassium from the blood-side to the lumen. 2. When K-transport is strongly depressed, either by withholding potassium from the blood side or by imposing a large positive potential on the lumen, the oxygen uptake of the isolated gut remains virtually unchanged. If the K-transport were to be energized by the negligible increase in oxygen uptake about 40 µ-equiv. of potassium would have to be transported for every µ-equiv. of extra oxygen taken up. This ratio of K-transport to oxygen uptake is thermodynamically impossible. 3. The ratio of potassium transported to total oxygen consumed when the midgut is bathed with 32 mM potassium on both sides is about 1.3 at temperatures of 25° and 15° C. The ratio must be smaller at lower potassium concentrations and is 2.0 at 73.5 mM-K, which may be approaching the maximum value. 4. Although the oxygen uptake is independent of the K-transport, the reverse is not true. There is a close dependency of K-transport on oxygen consumption. 5. K-transport by the midgut contrasts with Na-transport by the frog skin because Na-transport stimulates oxidative metabolism whereas K-transport does not. Evidently the coupling of transport to energy supply is different in the two systems.

scholarly journals UPHILL TRANSPORT INDUCED BY COUNTERFLOW

1957 ◽  
Vol 41 (2) ◽  
pp. 289-296 ◽  
Author(s):  
Thomas Rosenberg ◽  
W. Wilbrandt
Keyword(s):  
Transport System ◽  
Concentration Gradient ◽  
Flux Ratio ◽  
Mobile Carrier ◽  
Fixed Membrane ◽  
Feature Characteristic ◽  
Carrier Systems ◽  
Kinetic Treatment ◽  
Component Adsorption ◽  
Human Red Cells

1. In a membrane transport system containing a mobile carrier with affinities for two substrates a concentration gradient with respect to one of the substrates under certain conditions is able to induce an "uphill" transport (against the concentration gradient) of the other. 2. In a kinetic treatment quantitative conditions for such a "flow-induced uphill transport" and some of its characteristics are derived. 3. Experimentally the uphill transport of labelled glucose induced by a concentration gradient for mannose or unlabelled glucose is demonstrated in the human red cell. 4. It is shown that the flow-induced uphill transport is a feature characteristic for mobile carrier systems only and is not to be expected in systems in which the substrate is bound to a fixed membrane component ("adsorption membrane"), although such a system may yield identical transport kinetics. Also with respect to Ussing's flux ratio the two systems are different, the adsorption membrane meeting Ussing's criterion, the carrier membrane not. 5. It is concluded that the transport system in the human red cells must contain a mobile carrier, identical for glucose and mannose.

Sign in / Sign up

Export Citation Format

Share Document