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.

Organic cation transport by rat hepatocyte basolateral membrane vesicles

1992 ◽  
Vol 263 (6) ◽  
pp. G939-G946
Author(s):  
T. D. McKinney ◽  
M. A. Hosford
Keyword(s):  
Organic Cation ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Proton Exchange ◽  
Proton Gradient ◽  
Organic Cations ◽  
Maximal Velocity ◽  
Basolateral Membrane Vesicles ◽  
Rat Hepatocyte ◽  
Potassium Gradient

Hepatocyte basolateral membrane possesses transport systems for mediated uptake of organic cations, the first step in the subsequent biliary excretion and/or metabolism of these compounds. The purpose of these studies was to evaluate potential mechanisms for transport of this class of solutes across this membrane by measuring 3H-labeled tetraethylammonium ([3H]TEA) transport into rat hepatocyte basolateral membrane vesicles. [3H]TEA uptake was stimulated by an outwardly directed proton gradient consistent with TEA-proton exchange. Proton gradient-stimulated [3H]TEA uptake was inhibited by quinidine and by the combination of valinomycin and carbonyl cyanide m-chlorophenylhydrazone (CCCP) but not by CCCP alone or by N1-methylnicotinamide (NMN). An outwardly directed TEA gradient also stimulated uptake of [3H]TEA with values at early time points exceeding those at equilibrium. This trans-stimulation or countertransport was saturable with an apparent Michaelis constant of 106 microM and maximal velocity of 434 pmol.mg-1.15 s-1. TEA countertransport was cis-inhibited by quinidine, cimetidine, and thiamine and by low temperature, but not by NMN. Thiamine was also capable of trans-stimulating [3H]TEA uptake. An outwardly directed potassium gradient enhanced and an inwardly directed potassium gradient reduced TEA countertransport but had no effect on [3H]TEA uptake occurring in the absence of other electrochemical driving forces. These studies indicate that there are at least two potential mechanisms in the hepatocyte basolateral membrane for transport of organic cations; organic cation-organic cation exchange (countertransport) and organic cation-proton exchange. Furthermore, the results are consistent with the existence of more than one transporter with different substrate affinities in each of these categories.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Tetraethylammonium transport by OK cells.

1990 ◽  
Vol 1 (6) ◽  
pp. 902-909
Author(s):  
T D McKinney ◽  
M B Scheller ◽  
M Hosford ◽  
J A McAteer
Keyword(s):  
Organic Cation ◽  
Epithelial Transport ◽  
Proton Exchange ◽  
Proximal Tubules ◽  
Organic Cations ◽  
Kidney Cells ◽  
Dependent Manner ◽  
Transport Pathway ◽  
Opossum Kidney ◽  
Opossum Kidney Cells

Mechanisms exist in renal proximal tubules for the mediated transepithelial secretion or reabsorption of endogenous and exogenous organic cations. In the studies presented here, the uptake of the organic cation tetraethylammonium (TEA) into confluent monolayers of opossum kidney cells was evaluated to determine if these cells might serve as an in vitro model of this transport pathway. 3H-TEA entered opossum kidney cells in a time-dependent manner. Uptake at early time points was saturable with an apparent Km of 59.1 +/- 11.2 microM and a Vmax of 1,292 +/- 210 fmol/micrograms of DNA. TEA uptake was inhibited in a dose-dependent manner by several other organic cations including amiloride, cimetidine, verapamil, procainamide, quinidine and N1-methylnicotinamide. With 1 mM concentrations of these compounds, uptake was virtually eliminated. However, another organic cation, N'-methylnicotinamide caused only minimal inhibition. TEA uptake was significantly reduced by sodium azide, suggesting dependence on oxidative phosphorylation. An alkaline medium pH enhanced TEA uptake, but, at the same pH, uptake was similar in the presence or absence of bicarbonate. When cellular pH was altered by ammonium chloride addition or removal, TEA uptake was not affected. Thus, organic cation/proton exchange, as has been demonstrated previously in apical membrane vesicles prepared from proximal tubules, is evidently not responsible for TEA uptake. Similarly, uptake does not appear to result from organic cation/organic cation exchange. These results indicate that the plasma membrane of opossum kidney cells contains a transport system(s) for the mediated uptake of organic cations and that these cells may be a useful mode for further study of renal epithelial transport of these solutes.

Comparative insights into the mechanisms of renal organic anion and cation secretion

1991 ◽  
Vol 261 (6) ◽  
pp. R1329-R1340 ◽  
Author(s):  
J. B. Pritchard ◽  
D. S. Miller
Keyword(s):  
Organic Cation ◽  
Organic Anion ◽  
Basolateral Membrane ◽  
Cation Transport ◽  
Organic Anions ◽  
Proton Exchange ◽  
Metabolic Energy ◽  
Organic Cations ◽  
Free Concentration ◽  
Indirect Coupling

Comparative models have played a major role in defining the mechanisms that enable vertebrate proximal tubules to transport organic anions and cations from the peritubular interstitium to the urine. The unique advantages of these models and their contributions to our understanding of organic anion and cation transport mechanisms are summarized here. Recent studies of the organic anion transport system suggest that transport is coupled to metabolic energy via indirect coupling to the sodium gradient. Organic anions enter the cell across the basolateral membrane in exchange for alpha-ketoglutarate (alpha-KG), and the alpha-KG is returned to the interior via Na-alpha-KG cotransport. Indirect coupling to Na has been demonstrated in both isolated membranes and intact renal epithelial cells of species ranging from marine crustaceans to mammals. This mechanism was shown to drive not only cellular accumulation but also secretory transepithelial fluxes of organic anions. Luminal exit of secreted organic anions appears to be carrier mediated but is, at present, poorly understood, with mediated potential-driven efflux and anion exchange-driven efflux implicated in some species. As for organic anions, the renal clearance of some organic cations approaches the renal plasma flow. Although there is considerable variation in the handling of specific substrates between species, the basic properties of organic cation transport include carrier-mediated potential-driven uptake at the basolateral membrane, intracellular sequestration that reduces the free concentration of the cation, and luminal exit by organic cation-proton exchange. Reabsorptive transport is also observed for some organic cations, but its mechanisms and driving forces are not well understood.

scholarly journals Regulation Mechanisms of Expression and Function of Organic Cation Transporter 1

2021 ◽  
Vol 11 ◽  
Author(s):  
Giuliano Ciarimboli
Keyword(s):  
Organic Cation ◽  
Basolateral Membrane ◽  
Organic Cation Transporter ◽  
Organic Cations ◽  
Regulatory Processes ◽  
Organic Cation Transporter 1 ◽  
Exogenous Origin ◽  
And Function

The organic cation transporter 1 (OCT1) belongs together with OCT2 and OCT3 to the solute carrier family 22 (SLC22). OCTs are involved in the movement of organic cations through the plasma membrane. In humans, OCT1 is mainly expressed in the sinusoidal membrane of hepatocytes, while in rodents, OCT1 is strongly represented also in the basolateral membrane of renal proximal tubule cells. Considering that organic cations of endogenous origin are important neurotransmitters and that those of exogenous origin are important drugs, these transporters have significant physiological and pharmacological implications. Because of the high expression of OCTs in excretory organs, their activity has the potential to significantly impact not only local but also systemic concentration of their substrates. Even though many aspects governing OCT function, interaction with substrates, and pharmacological role have been extensively investigated, less is known about regulation of OCTs. Possible mechanisms of regulation include genetic and epigenetic modifications, rapid regulation processes induced by kinases, regulation caused by protein–protein interaction, and long-term regulation induced by specific metabolic and pathological situations. In this mini-review, the known regulatory processes of OCT1 expression and function obtained from in vitro and in vivo studies are summarized. Further research should be addressed to integrate this knowledge to known aspects of OCT1 physiology and pharmacology.

Transport processes of 2-deoxy-D-glucose in erythrocytes infected withPlasmodium yoelii, a rodent malaria parasite

Parasitology ◽  
1989 ◽  
Vol 98 (3) ◽  
pp. 371-379 ◽  
Author(s):  
A. Izumo ◽  
K. Tanabe ◽  
M. Kato ◽  
S. Doi ◽  
K. Maekawa ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Glucose Transporter ◽  
Plasmodium Yoelii ◽  
Transport Processes ◽  
Diffusion System ◽  
Host Cells ◽  
Metabolic Inhibitors ◽  
Dependent Manner ◽  
Simple Diffusion ◽  
Infected Cells

SUMMARYThe transport processes of D-glucose inPlasmodium yoelii-infected mouse erythrocytes were investigated using 2-deoxy-D-glucose (2DOG), a non-metabolizable analogue of D-glucose. Infected cells showed an increase in the uptake of 2DOG compared to uninfected controls, and an effect which was more prominent in cells with mature-stage parasites. Kinetic studies measuring the initial rates of 2DOG uptake revealed two components in infected cells with late trophozoite and schizont-stage parasites: a simple diffusion system and a carrier (transporter)-mediated system. The transporter was common for D-glucose and 2DOG and had a kinetic constant indicating a high affinity for 2DOG (theKm= 0·18 mM and theVmax= 0·61 mmol/1010cells/min), as compared to the constant of the mouse erythrocyte carrier (theKm= 10 mM and theVmax= 1·8 mmol/1010cells/min). Determination of the distribution of [3H]2DOG in infected cells and experiments with metabolic inhibitors indicated that the simple diffusion system localizes in the membrane of host cells and the transporter in the parasite plasma membrane. The parasite glucose transporter was much less sensitive to cytochalasin B than that of the host cells and the uptake of 2DOG via the transporter was dependent on energy. Based on these findings, the following features emerge: D-glucose first gains access to the cytosol of infected erythrocytes via the simple diffusion system, which appears after infection by the parasite, and an active uptake against the concentration gradient takes place at the parasite plasma membrane via the parasite glucose transporter in an energy dependent manner. Finally, an energy transduction mechanism for the transport of glucose across the parasite plasma membrane is discussed.

Uptake properties of lamivudine (3TC) by a continuous renal epithelial cell line

2001 ◽  
Vol 79 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Simon Leung ◽  
Reina Bendayan
Keyword(s):  
Epithelial Cell ◽  
Cell Line ◽  
Organic Cation ◽  
Exchange Process ◽  
Proton Exchange ◽  
Nucleoside Transport ◽  
Epithelial Cell Line ◽  
Dependent Manner ◽  
Renal Epithelial Cell ◽  
Renal Epithelial Cell Line

The purpose of this study was to characterize the renal uptake properties of the cytidine analog and antiretroviral agent 3TC. The uptake of radiolabelled 3TC was measured at 37°C in a continuous porcine renal epithelial cell line (i.e., LLC-PK1 cells) grown as a monolayer on an impermeable support. 3TC (5 µM) uptake (37°C) by the monolayer cells was saturable (Km = 1.2 ± 0.2 mM) but not significantly altered by various dideoxynucleoside analog drugs, nucleosides, and nucleoside transport inhibitors, suggesting that a nucleoside transporter is not involved in 3TC uptake. A number of endogenous organic cation probes and inhibitors significantly reduced 3TC uptake by the monolayer cells. Quinine, trimethoprim (TMP), and tetraethylammonium (TEA) inhibited 3TC uptake in a dose dependent manner with IC50 values of 0.6mM, 0.63mM, and 1.9 mM, respectively. In turn, the uptake of the typical organic cation substrate TEA was inhibited by high concentrations of 3TC. An outwardly directed proton gradient significantly increased the uptake of 3TC by the monolayer cells, suggesting the involvement of a proton exchange process. Conversely, in the presence of monensin, a Na+/H+ ionophore, the uptake of 3TC was significantly reduced. These results suggest that the uptake of 3TC by a cultured renal epithelium may be mediated by an organic cation-proton exchanger. The observed clinical interaction between 3TC and trimethoprim may be explained by competition for a common renal organic cation tubular transporter.Key words: 3TC, kidney, uptake, LLC-PK1, tubular elimination.

Characterization of tetraethylammonium uptake across the basolateral membrane of the Drosophila Malpighian (renal) tubule

2005 ◽  
Vol 289 (2) ◽  
pp. R495-R504 ◽  
Author(s):  
Mark R. Rheault ◽  
Donna M. Debicki ◽  
Michael J. O'Donnell
Keyword(s):  
Organic Cation ◽  
Basolateral Membrane ◽  
Transport Processes ◽  
Malpighian Tubules ◽  
Type I ◽  
Renal Tubules ◽  
Maximal Rate ◽  
High K ◽  
Total Transport ◽  
Low K

Basolateral transport of the prototypical type I organic cation tetraethylammonium (TEA) by the Malpighian tubules of Drosophila melanogaster was studied using measurements of basolateral membrane potential (Vbl) and uptake of [14C]-labeled TEA. TEA uptake was metabolically dependent and saturable (maximal rate of mediated TEA uptake by all potential transport processes, reflecting the total transport capacity of the membrane, 0.87 pmol·tubule−1·min−1; concentration of TEA at 0.5 of the maximal rate of TEA uptake value, 24 μM). TEA uptake in Malpighian tubules was inhibited by a number of type I (e.g., cimetidine, quinine, and TEA) and type II (e.g., verapamil) organic cations and was dependent on Vbl. TEA uptake was reduced in response to conditions that depolarized Vbl (high-K+ saline, Na+-free saline, NaCN) and increased in conditions that hyperpolarized Vbl (low-K+ saline). Addition of TEA to the saline bathing Malpighian tubules rapidly depolarized the Vbl, indicating that TEA uptake was electrogenic. Blockade of K+ channels with Ba2+ did not block effects of TEA on Vbl or TEA uptake indicating that TEA uptake does not occur through K+ channels. This is the first study to provide physiological evidence for an electrogenic carrier-mediated basolateral organic cation transport mechanism in insect Malpighian tubules. Our results also suggest that the mechanism of basolateral TEA uptake by Malpighian tubules is distinct from that found in vertebrate renal tubules.

scholarly journals Deficiency in the Organic Cation Transporters 1 and 2 (Oct1/Oct2 [Slc22a1/Slc22a2]) in Mice Abolishes Renal Secretion of Organic Cations

2003 ◽  
Vol 23 (21) ◽  
pp. 7902-7908 ◽  
Author(s):  
Johan W. Jonker ◽  
Els Wagenaar ◽  
Sven van Eijl ◽  
Alfred H. Schinkel
Keyword(s):  
Organic Cation ◽  
Basolateral Membrane ◽  
Hepatic Uptake ◽  
The Body ◽  
Organic Cations ◽  
Organic Cation Transporters ◽  
Renal Secretion ◽  
Double Knockout ◽  
Intestinal Excretion ◽  
Cation Transporters

ABSTRACT The polyspecific organic cation transporters 1 and 2 (Oct1 and -2) transport a broad range of substrates, including drugs, toxins, and endogenous compounds. Their strategic localization in the basolateral membrane of epithelial cells in the liver, intestine (Oct1), and kidney (Oct1 and Oct2) suggests that they play an essential role in removing noxious compounds from the body. We previously showed that in Oct1 −/− mice, the hepatic uptake and intestinal excretion of organic cations are greatly reduced. Since Oct1 and Oct2 have extensively overlapping substrate specificities, they might be functionally redundant. To investigate the pharmacologic and physiologic roles of these proteins, we generated Oct2 single-knockout and Oct1/2 double-knockout mice. Oct2 −/− and Oct1/2 −/− mice are viable and fertile and display no obvious phenotypic abnormalities. Absence of Oct2 in itself had little effect on the pharmacokinetics of tetraethylammonium (TEA), but in Oct1/2 −/− mice, renal secretion of this compound was completely abolished, leaving only glomerular filtration as a TEA clearance mechanism. As a consequence, levels of TEA were substantially increased in the plasma of Oct1/2 −/− mice. This study shows that Oct1 and Oct2 together are essential for renal secretion of (small) organic cations. A deficiency in these proteins may thus result in increased drug sensitivity and toxicity.

scholarly journals Properties of Transport Mediated by the Human Organic Cation Transporter 2 Studied in a Polarized Three-Dimensional Epithelial Cell Culture Model

2021 ◽  
Vol 22 (17) ◽  
pp. 9658
Author(s):  
Tim N. Koepp ◽  
Alexander Tokaj ◽  
Pavel I. Nedvetsky ◽  
Ana Carolina Conchon Costa ◽  
Beatrice Snieder ◽  
...  
Keyword(s):  
Organic Cation ◽  
Basolateral Membrane ◽  
Three Dimensional ◽  
Organic Cation Transporter ◽  
Organic Cations ◽  
Membrane Domain ◽  
Cell Culture Model ◽  
Hek Cells ◽  
Culture Model ◽  
Organic Cation Transporter 2

The renal secretory clearance for organic cations (neurotransmitters, metabolism products and drugs) is mediated by transporters specifically expressed in the basolateral and apical plasma membrane domains of proximal tubule cells. Here, human organic cation transporter 2 (hOCT2) is the main transporter for organic cations in the basolateral membrane domain. In this study, we stably expressed hOCT2 in Madin-Darby Canine Kidney (MDCK) cells and cultivated these cells in the presence of an extracellular matrix to obtain three-dimensional (3D) structures (cysts). The transport properties of hOCT2 expressed in MDCK cysts were compared with those measured using human embryonic kidney cells (HEK293) stably transfected with hOCT2 (hOCT2-HEK cells). In the MDCK cysts, hOCT2 was expressed in the basolateral membrane domain and showed a significant uptake of the fluorescent organic cation 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP+) with an affinity (Km) of 3.6 ± 1.2 µM, similar to what was measured in the hOCT2-HEK cells (Km = 3.1 ± 0.2 µM). ASP+ uptake was inhibited by tetraethylammonium (TEA+), tetrapentylammonium (TPA+), metformin and baricitinib both in the hOCT2-HEK cells and the hOCT2- MDCK cysts, even though the apparent affinities of TEA+ and baricitinib were dependent on the expression system. Then, hOCT2 was subjected to the same rapid regulation by inhibition of p56lck tyrosine kinase or calmodulin in the hOCT2-HEK cells and hOCT2- MDCK cysts. However, inhibition of casein kinase II regulated only activity of hOCT2 expressed in MDCK cysts and not in HEK cells. Taken together, these results suggest that the 3D cell culture model is a suitable tool for the functional analysis of hOCT2 transport properties, depending on cell polarization.

Membrane potential drives organic cation transport into teleost renal proximal tubules

1988 ◽  
Vol 255 (3) ◽  
pp. R492-R499 ◽  
Author(s):  
P. M. Smith ◽  
J. B. Pritchard ◽  
D. S. Miller
Keyword(s):  
Membrane Potential ◽  
Organic Cation ◽  
Basolateral Membrane ◽  
Cation Transport ◽  
K Channel ◽  
Organic Cation Transport ◽  
Renal Tubules ◽  
Dependent Manner ◽  
Cation Uptake ◽  
Basolateral Membrane Potential

The relationship between organic cation uptake and basolateral membrane potential was studied in renal tubules from two marine teleost fish, Southern flounder (Paralicthys lethostigma) and killifish (Fundulus heteroclitis). Carrier-mediated uptake of the model organic cation, tetraethylammonium (TEA), increased when K+ was changed from 2.5 to 0.2 mM and decreased when medium K+ was increased to 20 mM. Uptake was also reduced by the K+ channel blocker barium (1 mM). Furthermore, basolateral membrane potential hyperpolarized 15-25 mV in low-K+ medium and depolarized 30-40 mV in high-K+ medium. Barium also depolarized. Finally, basolateral membrane potential was depolarized in a concentration-dependent manner by addition of 100-500 microM TEA or Darstine. Thus treatments that hyperpolarize the basolateral membrane potential increase carrier-mediated TEA uptake, whereas those that depolarize basolateral membrane potential reduce uptake. Furthermore, organic cation transport into tubular cells involves the net influx of positive charge. Together, these findings support the argument that carrier-mediated organic cation uptake at the basolateral membrane is a potential-driven, electrogenic process.

Sign in / Sign up

Export Citation Format

Share Document