Model translocators for divalent and monovalent ion transport in phospholipid membranes

1974 ◽  
Vol 18 (1) ◽  
pp. 201-218 ◽  
Author(s):  
Sergio Estrada-O. ◽  
Heliodoro Célis ◽  
Esthela Calderón ◽  
Guadalupe Gallo ◽  
M. Montal
Keyword(s):  
Ion Transport ◽  
Phospholipid Membranes ◽  
Monovalent Ion

Vasopressin stimulates DNA synthesis and ion transport in quiescent epithelial cells

1985 ◽  
Vol 249 (3) ◽  
pp. C267-C270 ◽  
Author(s):  
V. M. Reznik ◽  
R. J. Shapiro ◽  
S. A. Mendoza
Keyword(s):  
Epithelial Cells ◽  
Dna Synthesis ◽  
Ion Transport ◽  
Growth Regulation ◽  
Mdck Cells ◽  
Subsequent Increase ◽  
Low Concentrations ◽  
Pump Activity ◽  
Monovalent Ion ◽  
Na Uptake

The mitogenic effect of vasopressin was studied in subconfluent quiescent renal epithelial cells (MDCK). Vasopressin stimulated DNA synthesis in the presence of low concentrations of serum. Vasopressin increased the entry of Na into the cells and increased ouabain-sensitive 86Rb uptake, a measure of Na-K pump activity. Because the activity of the Na-K pump in MDCK cells is steeply dependent on intracellular Na, it is likely that stimulation of the Na-K pump by vasopressin was mediated by the increase in Na entry into the cells. Thus both serum and vasopressin stimulate Na uptake and Na-K pump activity in quiescent MDCK cells with a subsequent increase in DNA synthesis. It is concluded that growth regulation in epithelial cells may be mediated in part by changes in monovalent ion transport.

Short-circuit current measurements in proximal tubule of Necturus kidney

1961 ◽  
Vol 201 (1) ◽  
pp. 157-163 ◽  
Author(s):  
Friedrich Wilhelm Eigler
Keyword(s):  
Ion Transport ◽  
Proximal Tubule ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Proper Position ◽  
Indifferent Electrode ◽  
Tubular Lumen ◽  
Active Ion Transport ◽  
Monovalent Ion

A modified short-circuit method, which requires only one pair of electrodes, was applied to the proximal tubule of the Necturus kidney for determination of the short-circuit current as a measure of active ion transport across the tubular wall. The indifferent electrode was placed on the surface of the exposed kidney and the tubular lumen was punctured with a microelectrode. After injection of oil into the glomerulus of the same nephron, a marked increase in electrical resistance between the electrodes during oil passage at the puncture site indicated the proper position of the electrode tip in the tubular lumen. The largest area effectively short-circuited (12.5 x 10–4 cm2) was determined by changing the position of two oil droplets between which measurements were made. Thirteen measurements of the short-circuit current in anesthetized normal Necturi averaged 4.8 x 10–6 amp/cm2, which corresponds to an active monovalent ion transport of 4.6 x 10–11 Eq/cm2 x sec.

Developmental Aspects of Fluid and Electrolyte Secretion in Salivary Glands

1994 ◽  
Vol 5 (3) ◽  
pp. 281-290 ◽  
Author(s):  
J. Ricardo Martinez
Keyword(s):  
Signal Transduction ◽  
Ion Transport ◽  
Salivary Glands ◽  
Signal Transduction Pathway ◽  
Cholinergic Receptors ◽  
Transport Systems ◽  
Secretory Process ◽  
Osmotic Gradient ◽  
Monovalent Ion ◽  
Electrolyte Secretion

The salivary glands of rodents undergo considerable cytodifferentiation after birth and are useful models for the study of functional development, including the mechanisms of fluid and electrolyte secretion. In the rat submandibular gland, secretion of salivary fluid cannot be elicited until approximately 2 weeks of age. The currently accepted model of salivary fluid secretion indicates that this process depends on the activation, on stimulation of cholinergic receptors, of several ion transport systems, resulting in a net transport of osmotically active ions (primarily Cl- and Na +) across the acinar epithelium. This creates the necessary osmotic gradient for the transacinar movement of water. The process is associated with a signal transduction pathway involving the formation of phosphoinositide products (primarily inositol triphosphate or IP3) and the mobilization of Ca2+. The latter regulates monovalent ion conductances (K+, CI-), which are critical for the secretory process. Immature submandibular glands and cells of early postnatal rats have a lower density of cholinergic receptors and release less K+ and Cl- than mature cells and gradually develop other ion transport systems (such as a Na, K, 2Cl cotransport system) involved in the secretory process. Surprisingly, they form more IP3 and show a larger increase in cytosolic Ca2+ when stimulated with maximal or supramaximal concentrations of agonist. Therefore, they show some interesting dissociations in the signal transduction mechanism that suggest differences in the coupling between receptors and membrane phosphoinositides, between IP3 and IP3-dependent Ca2+ stores, and between the Ca2+ signal and the monovalent ion transport systems which are critical for secretion.

Localization of Ion-Transport in the Intestine Of The Migrating River Lamprey, Lampetra Fluviatilis L

1973 ◽  
Vol 58 (1) ◽  
pp. 165-176
Author(s):  
ALAN D. PICKERING ◽  
R. MORRIS
Keyword(s):  
Ion Transport ◽  
Sea Water ◽  
Water Flux ◽  
Ion Flux ◽  
Lampetra Fluviatilis ◽  
River Lamprey ◽  
Monovalent Ions ◽  
Anterior Intestine ◽  
Monovalent Ion ◽  
Columnar Cells

1. Isolated intestinal preparations from migrating Lampetra fluviatilis re-adapted to 50% sea water were used to localize ion transport. 2. A large, active, monovalent-ion flux was found in the anterior intestine and its magnitude decreased towards the posterior end of the intestine. 3. The monovalent-ion flux is responsible for a net water flux from mucosa to serosa in the anterior intestine. 4. It is tentatively suggested that both sodium and chloride are actively transported by the mucosa. The divalent ions may be carried along with the monovalent ions to a limited extent. 5. Studies at the light- and electron-microscope levels indicate that columnar cells of the anterior intestine are responsible for ion transport, and there is evidence that the same cells produce mucus.

scholarly journals Early events elicited by bombesin and structurally related peptides in quiescent Swiss 3T3 cells. II. Changes in Na+ and Ca2+ fluxes, Na+/K+ pump activity, and intracellular pH.

1986 ◽  
Vol 102 (6) ◽  
pp. 2223-2233 ◽  
Author(s):  
S A Mendoza ◽  
J A Schneider ◽  
A Lopez-Rivas ◽  
J W Sinnett-Smith ◽  
E Rozengurt
Keyword(s):  
Ion Transport ◽  
Intracellular Ph ◽  
Free Calcium ◽  
3T3 Cells ◽  
Phosphotransferase System ◽  
Phorbol Dibutyrate ◽  
Protein Kinase C Activity ◽  
Pump Activity ◽  
Monovalent Ion ◽  
Swiss 3T3

The amphibian tetradecapeptide, bombesin, and structurally related peptides caused a marked increase in ouabain-sensitive 86Rb+ uptake (a measure of Na+/K+ pump activity) in quiescent Swiss 3T3 cells. This effect occurred within seconds after the addition of the peptide and appeared to be mediated by an increase in Na+ entry into the cells. The effect of bombesin on Na+ entry and Na+/K+ pump activity was concentration dependent with half-maximal stimulation occurring at 0.3-0.4 nM. The structurally related peptides litorin, gastrin-releasing peptide, and neuromedin B also stimulated ouabain-sensitive 86Rb+ uptake; the relative potencies of these peptides in stimulating the Na+/K+ pump were comparable to their potencies in increasing DNA synthesis (Zachary, I., and E. Rozengurt, 1985, Proc. Natl. Acad. Sci. USA., 82:7616-7620). Bombesin increased Na+ influx, at least in part, through an Na+/H+ antiport. The peptide augmented intracellular pH and this effect was abolished in the absence of extracellular Na+. In addition to monovalent ion transport, bombesin and the structurally related peptides rapidly increased the efflux of 45Ca2+ from quiescent Swiss 3T3 cells. This Ca2+ came from an intracellular pool and the efflux was associated with a 50% decrease in total intracellular Ca2+. The peptides also caused a rapid increase in cytosolic free calcium concentration. Prolonged pretreatment of Swiss 3T3 cells with phorbol dibutyrate, which causes a loss of protein kinase C activity (Rodriguez-Pena, A., and E. Rozengurt, 1984, Biochem. Biophys. Res. Commun., 120:1053-1059), greatly decreased the stimulation of 86Rb+ uptake and Na+ entry by bombesin implicating this phosphotransferase system in the mediation of part of these responses to bombesin. Since some activation of monovalent ion transport by bombesin was seen in phorbol dibutyrate-pretreated cells, it is likely that the peptide also stimulates monovalent ion transport by a second mechanism.

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